diff --git a/backend/Dockerfile b/backend/Dockerfile
index 7c63c4b8..4226aa3a 100644
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@@ -1,11 +1,14 @@
-FROM node:22 AS build-stage
+FROM node:22
 
-WORKDIR /app
+WORKDIR /app/dwengo
+
+COPY ./backend/i18n ./i18n
 
 # Install dependencies
 
 COPY package*.json ./
 COPY backend/package.json ./backend/
+COPY common/package.json ./common/
 
 RUN npm install --silent
 
@@ -14,25 +17,13 @@ RUN npm install --silent
 # Root tsconfig.json
 COPY tsconfig.json ./
 
-WORKDIR /app/backend
+COPY backend ./backend
+COPY common ./common
+COPY docs ./docs
 
-COPY backend ./
-COPY docs /app/docs
-
-RUN npm run build
-
-FROM node:22 AS production-stage
-
-WORKDIR /app
-
-COPY package-lock.json backend/package.json ./
-
-RUN npm install --silent --only=production
-
-COPY ./docs /docs
-COPY ./backend/i18n /app/i18n
-COPY --from=build-stage /app/backend/dist ./dist/
+RUN npm run build --workspace=common
+RUN npm run build --workspace=backend
 
 EXPOSE 3000
 
-CMD ["node", "--env-file=.env", "dist/app.js"]
+CMD ["node", "--env-file=/app/dwengo/backend/.env", "/app/dwengo/backend/dist/app.js"]
diff --git a/backend/package.json b/backend/package.json
index c08fb1dc..c09ac285 100644
--- a/backend/package.json
+++ b/backend/package.json
@@ -24,6 +24,7 @@
         "cross": "^1.0.0",
         "cross-env": "^7.0.3",
         "dotenv": "^16.4.7",
+        "dwengo-1-common": "^0.1.1",
         "express": "^5.0.1",
         "express-jwt": "^8.5.1",
         "gift-pegjs": "^1.0.2",
diff --git a/backend/src/controllers/assignments.ts b/backend/src/controllers/assignments.ts
index c8dd1ec8..21bd568c 100644
--- a/backend/src/controllers/assignments.ts
+++ b/backend/src/controllers/assignments.ts
@@ -1,6 +1,7 @@
 import { Request, Response } from 'express';
 import { createAssignment, getAllAssignments, getAssignment, getAssignmentsSubmissions } from '../services/assignments.js';
-import { AssignmentDTO } from '../interfaces/assignment.js';
+
+import { AssignmentDTO } from 'dwengo-1-common/src/interfaces/assignment';
 
 // Typescript is annoying with parameter forwarding from class.ts
 interface AssignmentParams {
diff --git a/backend/src/controllers/classes.ts b/backend/src/controllers/classes.ts
index 7526f7c4..40683c6a 100644
--- a/backend/src/controllers/classes.ts
+++ b/backend/src/controllers/classes.ts
@@ -1,6 +1,7 @@
 import { Request, Response } from 'express';
 import { createClass, getAllClasses, getClass, getClassStudents, getClassStudentsIds, getClassTeacherInvitations } from '../services/classes.js';
-import { ClassDTO } from '../interfaces/class.js';
+
+import { ClassDTO } from 'dwengo-1-common/src/interfaces/class';
 
 export async function getAllClassesHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
diff --git a/backend/src/controllers/groups.ts b/backend/src/controllers/groups.ts
index 7de3e114..6258cb20 100644
--- a/backend/src/controllers/groups.ts
+++ b/backend/src/controllers/groups.ts
@@ -1,6 +1,7 @@
 import { Request, Response } from 'express';
 import { createGroup, getAllGroups, getGroup, getGroupSubmissions } from '../services/groups.js';
-import { GroupDTO } from '../interfaces/group.js';
+
+import { GroupDTO } from 'dwengo-1-common/src/interfaces/group';
 
 // Typescript is annoywith with parameter forwarding from class.ts
 interface GroupParams {
diff --git a/backend/src/controllers/learning-objects.ts b/backend/src/controllers/learning-objects.ts
index fc79ef0d..710999ce 100644
--- a/backend/src/controllers/learning-objects.ts
+++ b/backend/src/controllers/learning-objects.ts
@@ -1,12 +1,12 @@
 import { Request, Response } from 'express';
 import { FALLBACK_LANG } from '../config.js';
-import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '../interfaces/learning-content.js';
 import learningObjectService from '../services/learning-objects/learning-object-service.js';
 import { envVars, getEnvVar } from '../util/envVars.js';
 import { Language } from '../entities/content/language.js';
 import attachmentService from '../services/learning-objects/attachment-service.js';
 import { NotFoundError } from '@mikro-orm/core';
 import { BadRequestException } from '../exceptions/bad-request-exception.js';
+import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from 'dwengo-1-common/src/interfaces/learning-content';
 
 function getLearningObjectIdentifierFromRequest(req: Request): LearningObjectIdentifier {
     if (!req.params.hruid) {
diff --git a/backend/src/controllers/questions.ts b/backend/src/controllers/questions.ts
index 6735c305..089931f3 100644
--- a/backend/src/controllers/questions.ts
+++ b/backend/src/controllers/questions.ts
@@ -1,9 +1,9 @@
 import { Request, Response } from 'express';
 import { createQuestion, deleteQuestion, getAllQuestions, getAnswersByQuestion, getQuestion } from '../services/questions.js';
-import { QuestionDTO, QuestionId } from '../interfaces/question.js';
 import { FALLBACK_LANG, FALLBACK_SEQ_NUM } from '../config.js';
 import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
 import { Language } from '../entities/content/language.js';
+import { QuestionDTO, QuestionId } from 'dwengo-1-common/src/interfaces/question';
 
 function getObjectId(req: Request, res: Response): LearningObjectIdentifier | null {
     const { hruid, version } = req.params;
diff --git a/backend/src/controllers/submissions.ts b/backend/src/controllers/submissions.ts
index 67c1d3a9..df0f6e48 100644
--- a/backend/src/controllers/submissions.ts
+++ b/backend/src/controllers/submissions.ts
@@ -1,7 +1,8 @@
 import { Request, Response } from 'express';
 import { createSubmission, deleteSubmission, getSubmission } from '../services/submissions.js';
 import { Language, languageMap } from '../entities/content/language.js';
-import { SubmissionDTO } from '../interfaces/submission';
+
+import { SubmissionDTO } from 'dwengo-1-common/src/interfaces/submission';
 
 interface SubmissionParams {
     hruid: string;
diff --git a/backend/src/entities/content/learning-object.entity.ts b/backend/src/entities/content/learning-object.entity.ts
index e352a10a..db009e7a 100644
--- a/backend/src/entities/content/learning-object.entity.ts
+++ b/backend/src/entities/content/learning-object.entity.ts
@@ -1,11 +1,11 @@
 import { Embedded, Entity, Enum, ManyToMany, OneToMany, PrimaryKey, Property } from '@mikro-orm/core';
-import { Language } from './language.js';
 import { Attachment } from './attachment.entity.js';
 import { Teacher } from '../users/teacher.entity.js';
 import { DwengoContentType } from '../../services/learning-objects/processing/content-type.js';
 import { v4 } from 'uuid';
 import { LearningObjectRepository } from '../../data/content/learning-object-repository.js';
 import { EducationalGoal } from './educational-goal.entity.js';
+import { Language } from './language.js';
 import { ReturnValue } from './return-value.entity.js';
 
 @Entity({ repository: () => LearningObjectRepository })
diff --git a/backend/src/interfaces/answer.ts b/backend/src/interfaces/answer.ts
index 1162a1d3..f268730a 100644
--- a/backend/src/interfaces/answer.ts
+++ b/backend/src/interfaces/answer.ts
@@ -1,14 +1,7 @@
-import { mapToUserDTO, UserDTO } from './user.js';
-import {mapToQuestionDTO, mapToQuestionDTOId, QuestionDTO, QuestionId} from './question.js';
+import { mapToUserDTO } from './user.js';
+import { mapToQuestionDTO, mapToQuestionDTOId } from './question.js';
 import { Answer } from '../entities/questions/answer.entity.js';
-
-export interface AnswerDTO {
-    author: UserDTO;
-    toQuestion: QuestionDTO;
-    sequenceNumber: number;
-    timestamp: string;
-    content: string;
-}
+import { AnswerDTO, AnswerId } from 'dwengo-1-common/src/interfaces/answer';
 
 /**
  * Convert a Question entity to a DTO format.
@@ -23,16 +16,10 @@ export function mapToAnswerDTO(answer: Answer): AnswerDTO {
     };
 }
 
-export interface AnswerId {
-    author: string;
-    toQuestion: QuestionId;
-    sequenceNumber: number;
-}
-
-export function mapToAnswerDTOId(answer: Answer): AnswerId {
+export function mapToAnswerId(answer: AnswerDTO): AnswerId {
     return {
         author: answer.author.username,
         toQuestion: mapToQuestionDTOId(answer.toQuestion),
-        sequenceNumber: answer.sequenceNumber!,
+        sequenceNumber: answer.sequenceNumber,
     };
 }
diff --git a/backend/src/interfaces/assignment.ts b/backend/src/interfaces/assignment.ts
index 698b5b40..84cbd0cf 100644
--- a/backend/src/interfaces/assignment.ts
+++ b/backend/src/interfaces/assignment.ts
@@ -1,19 +1,9 @@
 import { FALLBACK_LANG } from '../config.js';
 import { Assignment } from '../entities/assignments/assignment.entity.js';
 import { Class } from '../entities/classes/class.entity.js';
-import { languageMap } from '../entities/content/language.js';
-import { GroupDTO } from './group.js';
 import { getLogger } from '../logging/initalize.js';
-
-export interface AssignmentDTO {
-    id: number;
-    class: string; // Id of class 'within'
-    title: string;
-    description: string;
-    learningPath: string;
-    language: string;
-    groups?: GroupDTO[] | string[]; // TODO
-}
+import { languageMap } from '../entities/content/language.js';
+import { AssignmentDTO } from 'dwengo-1-common/src/interfaces/assignment';
 
 export function mapToAssignmentDTOId(assignment: Assignment): AssignmentDTO {
     return {
diff --git a/backend/src/interfaces/class.ts b/backend/src/interfaces/class.ts
index ea1d4901..c711b94b 100644
--- a/backend/src/interfaces/class.ts
+++ b/backend/src/interfaces/class.ts
@@ -2,14 +2,7 @@ import { Collection } from '@mikro-orm/core';
 import { Class } from '../entities/classes/class.entity.js';
 import { Student } from '../entities/users/student.entity.js';
 import { Teacher } from '../entities/users/teacher.entity.js';
-
-export interface ClassDTO {
-    id: string;
-    displayName: string;
-    teachers: string[];
-    students: string[];
-    joinRequests: string[];
-}
+import { ClassDTO } from 'dwengo-1-common/src/interfaces/class';
 
 export function mapToClassDTO(cls: Class): ClassDTO {
     return {
diff --git a/backend/src/interfaces/group.ts b/backend/src/interfaces/group.ts
index a25c5b8e..9f71e3f7 100644
--- a/backend/src/interfaces/group.ts
+++ b/backend/src/interfaces/group.ts
@@ -1,12 +1,7 @@
 import { Group } from '../entities/assignments/group.entity.js';
-import { AssignmentDTO, mapToAssignmentDTO } from './assignment.js';
-import { mapToStudentDTO, StudentDTO } from './student.js';
-
-export interface GroupDTO {
-    assignment: number | AssignmentDTO;
-    groupNumber: number;
-    members: string[] | StudentDTO[];
-}
+import { mapToAssignmentDTO } from './assignment.js';
+import { mapToStudentDTO } from './student.js';
+import { GroupDTO } from 'dwengo-1-common/src/interfaces/group';
 
 export function mapToGroupDTO(group: Group): GroupDTO {
     return {
diff --git a/backend/src/interfaces/question.ts b/backend/src/interfaces/question.ts
index b46e324f..e4b1eb8f 100644
--- a/backend/src/interfaces/question.ts
+++ b/backend/src/interfaces/question.ts
@@ -1,14 +1,6 @@
 import { Question } from '../entities/questions/question.entity.js';
-import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
-import { mapToStudentDTO, StudentDTO } from './student.js';
-
-export interface QuestionDTO {
-    learningObjectIdentifier: LearningObjectIdentifier;
-    sequenceNumber?: number;
-    author: StudentDTO;
-    timestamp?: string;
-    content: string;
-}
+import { mapToStudentDTO } from './student.js';
+import { QuestionDTO, QuestionId } from 'dwengo-1-common/src/interfaces/question';
 
 function getLearningObjectIdentifier(question: Question): LearningObjectIdentifier {
     return {
@@ -33,11 +25,6 @@ export function mapToQuestionDTO(question: Question): QuestionDTO {
     };
 }
 
-export interface QuestionId {
-    learningObjectIdentifier: LearningObjectIdentifier;
-    sequenceNumber: number;
-}
-
 export function mapToQuestionDTOId(question: Question): QuestionId {
     const learningObjectIdentifier = getLearningObjectIdentifier(question);
 
diff --git a/backend/src/interfaces/student.ts b/backend/src/interfaces/student.ts
index 5297939a..e1e4253f 100644
--- a/backend/src/interfaces/student.ts
+++ b/backend/src/interfaces/student.ts
@@ -1,12 +1,6 @@
 import { Student } from '../entities/users/student.entity.js';
 import { getStudentRepository } from '../data/repositories.js';
-
-export interface StudentDTO {
-    id: string;
-    username: string;
-    firstName: string;
-    lastName: string;
-}
+import { StudentDTO } from 'dwengo-1-common/src/interfaces/student';
 
 export function mapToStudentDTO(student: Student): StudentDTO {
     return {
diff --git a/backend/src/interfaces/submission.ts b/backend/src/interfaces/submission.ts
index 98cc4f22..9a506b27 100644
--- a/backend/src/interfaces/submission.ts
+++ b/backend/src/interfaces/submission.ts
@@ -1,26 +1,7 @@
 import { Submission } from '../entities/assignments/submission.entity.js';
-import { Language } from '../entities/content/language.js';
-import { GroupDTO, mapToGroupDTO } from './group.js';
-import { mapToStudent, mapToStudentDTO, StudentDTO } from './student.js';
-import { LearningObjectIdentifier } from './learning-content.js';
-
-export interface SubmissionDTO {
-    learningObjectIdentifier: LearningObjectIdentifier;
-
-    submissionNumber?: number;
-    submitter: StudentDTO;
-    time?: Date;
-    group?: GroupDTO;
-    content: string;
-}
-
-export interface SubmissionDTOId {
-    learningObjectHruid: string;
-    learningObjectLanguage: Language;
-    learningObjectVersion: number;
-
-    submissionNumber?: number;
-}
+import { mapToGroupDTO } from './group.js';
+import { mapToStudent, mapToStudentDTO } from './student.js';
+import { SubmissionDTO, SubmissionDTOId } from 'dwengo-1-common/src/interfaces/submission';
 
 export function mapToSubmissionDTO(submission: Submission): SubmissionDTO {
     return {
diff --git a/backend/src/interfaces/teacher-invitation.ts b/backend/src/interfaces/teacher-invitation.ts
index cddef566..8df92fd1 100644
--- a/backend/src/interfaces/teacher-invitation.ts
+++ b/backend/src/interfaces/teacher-invitation.ts
@@ -1,12 +1,7 @@
 import { TeacherInvitation } from '../entities/classes/teacher-invitation.entity.js';
-import { ClassDTO, mapToClassDTO } from './class.js';
-import { mapToUserDTO, UserDTO } from './user.js';
-
-export interface TeacherInvitationDTO {
-    sender: string | UserDTO;
-    receiver: string | UserDTO;
-    class: string | ClassDTO;
-}
+import { mapToClassDTO } from './class.js';
+import { mapToUserDTO } from './user.js';
+import { TeacherInvitationDTO } from 'dwengo-1-common/src/interfaces/teacher-invitation';
 
 export function mapToTeacherInvitationDTO(invitation: TeacherInvitation): TeacherInvitationDTO {
     return {
diff --git a/backend/src/interfaces/teacher.ts b/backend/src/interfaces/teacher.ts
index 31b4723f..a1ba33fd 100644
--- a/backend/src/interfaces/teacher.ts
+++ b/backend/src/interfaces/teacher.ts
@@ -1,18 +1,6 @@
 import { Teacher } from '../entities/users/teacher.entity.js';
 import { getTeacherRepository } from '../data/repositories.js';
-
-export interface TeacherDTO {
-    id: string;
-    username: string;
-    firstName: string;
-    lastName: string;
-    endpoints?: {
-        classes: string;
-        questions: string;
-        invitations: string;
-        groups: string;
-    };
-}
+import { TeacherDTO } from 'dwengo-1-common/src/interfaces/teacher';
 
 export function mapToTeacherDTO(teacher: Teacher): TeacherDTO {
     return {
diff --git a/backend/src/interfaces/user.ts b/backend/src/interfaces/user.ts
index 58f0dd5a..ecc9dd77 100644
--- a/backend/src/interfaces/user.ts
+++ b/backend/src/interfaces/user.ts
@@ -1,17 +1,5 @@
 import { User } from '../entities/users/user.entity.js';
-
-export interface UserDTO {
-    id?: string;
-    username: string;
-    firstName: string;
-    lastName: string;
-    endpoints?: {
-        self: string;
-        classes: string;
-        questions: string;
-        invitations: string;
-    };
-}
+import { UserDTO } from 'dwengo-1-common/src/interfaces/user';
 
 export function mapToUserDTO(user: User): UserDTO {
     return {
diff --git a/backend/src/services/assignments.ts b/backend/src/services/assignments.ts
index 22c5ce9e..62ea31e6 100644
--- a/backend/src/services/assignments.ts
+++ b/backend/src/services/assignments.ts
@@ -1,6 +1,8 @@
 import { getAssignmentRepository, getClassRepository, getGroupRepository, getSubmissionRepository } from '../data/repositories.js';
-import { AssignmentDTO, mapToAssignment, mapToAssignmentDTO, mapToAssignmentDTOId } from '../interfaces/assignment.js';
-import { mapToSubmissionDTO, mapToSubmissionDTOId, SubmissionDTO, SubmissionDTOId } from '../interfaces/submission.js';
+import { mapToAssignment, mapToAssignmentDTO, mapToAssignmentDTOId } from '../interfaces/assignment.js';
+import { mapToSubmissionDTO, mapToSubmissionDTOId } from '../interfaces/submission.js';
+import { AssignmentDTO } from 'dwengo-1-common/src/interfaces/assignment';
+import { SubmissionDTO, SubmissionDTOId } from 'dwengo-1-common/src/interfaces/submission';
 import { getLogger } from '../logging/initalize.js';
 
 export async function getAllAssignments(classid: string, full: boolean): Promise<AssignmentDTO[]> {
diff --git a/backend/src/services/classes.ts b/backend/src/services/classes.ts
index 7e773fbf..42f4640f 100644
--- a/backend/src/services/classes.ts
+++ b/backend/src/services/classes.ts
@@ -1,10 +1,13 @@
 import { getClassRepository, getStudentRepository, getTeacherInvitationRepository, getTeacherRepository } from '../data/repositories.js';
-import { ClassDTO, mapToClassDTO } from '../interfaces/class.js';
-import { mapToStudentDTO, StudentDTO } from '../interfaces/student.js';
-import { mapToTeacherInvitationDTO, mapToTeacherInvitationDTOIds, TeacherInvitationDTO } from '../interfaces/teacher-invitation.js';
+import { mapToClassDTO } from '../interfaces/class.js';
+import { mapToStudentDTO } from '../interfaces/student.js';
+import { mapToTeacherInvitationDTO, mapToTeacherInvitationDTOIds } from '../interfaces/teacher-invitation.js';
 import { getLogger } from '../logging/initalize.js';
 import { NotFoundException } from '../exceptions/not-found-exception.js';
 import { Class } from '../entities/classes/class.entity.js';
+import { ClassDTO } from 'dwengo-1-common/src/interfaces/class';
+import { TeacherInvitationDTO } from 'dwengo-1-common/src/interfaces/teacher-invitation';
+import { StudentDTO } from 'dwengo-1-common/src/interfaces/student';
 
 const logger = getLogger();
 
diff --git a/backend/src/services/groups.ts b/backend/src/services/groups.ts
index 16895e0a..5d35de55 100644
--- a/backend/src/services/groups.ts
+++ b/backend/src/services/groups.ts
@@ -6,8 +6,10 @@ import {
     getSubmissionRepository,
 } from '../data/repositories.js';
 import { Group } from '../entities/assignments/group.entity.js';
-import { GroupDTO, mapToGroupDTO, mapToGroupDTOId } from '../interfaces/group.js';
-import { mapToSubmissionDTO, mapToSubmissionDTOId, SubmissionDTO, SubmissionDTOId } from '../interfaces/submission.js';
+import { mapToGroupDTO, mapToGroupDTOId } from '../interfaces/group.js';
+import { mapToSubmissionDTO, mapToSubmissionDTOId } from '../interfaces/submission.js';
+import { GroupDTO } from 'dwengo-1-common/src/interfaces/group';
+import { SubmissionDTO, SubmissionDTOId } from 'dwengo-1-common/src/interfaces/submission';
 import { getLogger } from '../logging/initalize.js';
 
 export async function getGroup(classId: string, assignmentNumber: number, groupNumber: number, full: boolean): Promise<GroupDTO | null> {
diff --git a/backend/src/services/learning-objects.ts b/backend/src/services/learning-objects.ts
index 43af1aca..6dfd2704 100644
--- a/backend/src/services/learning-objects.ts
+++ b/backend/src/services/learning-objects.ts
@@ -1,6 +1,12 @@
 import { DWENGO_API_BASE } from '../config.js';
 import { fetchWithLogging } from '../util/api-helper.js';
-import { FilteredLearningObject, LearningObjectMetadata, LearningObjectNode, LearningPathResponse } from '../interfaces/learning-content.js';
+
+import {
+    FilteredLearningObject,
+    LearningObjectMetadata,
+    LearningObjectNode,
+    LearningPathResponse,
+} from 'dwengo-1-common/src/interfaces/learning-content';
 import { getLogger } from '../logging/initalize.js';
 
 function filterData(data: LearningObjectMetadata, htmlUrl: string): FilteredLearningObject {
diff --git a/backend/src/services/learning-objects/attachment-service.ts b/backend/src/services/learning-objects/attachment-service.ts
index 4ff4ec47..2acf90a0 100644
--- a/backend/src/services/learning-objects/attachment-service.ts
+++ b/backend/src/services/learning-objects/attachment-service.ts
@@ -1,6 +1,7 @@
 import { getAttachmentRepository } from '../../data/repositories.js';
 import { Attachment } from '../../entities/content/attachment.entity.js';
-import { LearningObjectIdentifier } from '../../interfaces/learning-content.js';
+
+import { LearningObjectIdentifier } from 'dwengo-1-common/src/interfaces/learning-content';
 
 const attachmentService = {
     async getAttachment(learningObjectId: LearningObjectIdentifier, attachmentName: string): Promise<Attachment | null> {
diff --git a/backend/src/services/learning-objects/database-learning-object-provider.ts b/backend/src/services/learning-objects/database-learning-object-provider.ts
index a8055f2c..0639782c 100644
--- a/backend/src/services/learning-objects/database-learning-object-provider.ts
+++ b/backend/src/services/learning-objects/database-learning-object-provider.ts
@@ -1,5 +1,4 @@
 import { LearningObjectProvider } from './learning-object-provider.js';
-import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '../../interfaces/learning-content.js';
 import { getLearningObjectRepository, getLearningPathRepository } from '../../data/repositories.js';
 import { LearningObject } from '../../entities/content/learning-object.entity.js';
 import { getUrlStringForLearningObject } from '../../util/links.js';
@@ -7,6 +6,7 @@ import processingService from './processing/processing-service.js';
 import { NotFoundError } from '@mikro-orm/core';
 import learningObjectService from './learning-object-service.js';
 import { getLogger, Logger } from '../../logging/initalize.js';
+import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from 'dwengo-1-common/src/interfaces/learning-content';
 
 const logger: Logger = getLogger();
 
diff --git a/backend/src/services/learning-objects/dwengo-api-learning-object-provider.ts b/backend/src/services/learning-objects/dwengo-api-learning-object-provider.ts
index dfee329d..35d9f899 100644
--- a/backend/src/services/learning-objects/dwengo-api-learning-object-provider.ts
+++ b/backend/src/services/learning-objects/dwengo-api-learning-object-provider.ts
@@ -1,5 +1,8 @@
 import { DWENGO_API_BASE } from '../../config.js';
 import { fetchWithLogging } from '../../util/api-helper.js';
+import dwengoApiLearningPathProvider from '../learning-paths/dwengo-api-learning-path-provider.js';
+import { LearningObjectProvider } from './learning-object-provider.js';
+import { getLogger, Logger } from '../../logging/initalize.js';
 import {
     FilteredLearningObject,
     LearningObjectIdentifier,
@@ -7,10 +10,7 @@ import {
     LearningObjectNode,
     LearningPathIdentifier,
     LearningPathResponse,
-} from '../../interfaces/learning-content.js';
-import dwengoApiLearningPathProvider from '../learning-paths/dwengo-api-learning-path-provider.js';
-import { LearningObjectProvider } from './learning-object-provider.js';
-import { getLogger, Logger } from '../../logging/initalize.js';
+} from 'dwengo-1-common/src/interfaces/learning-content';
 
 const logger: Logger = getLogger();
 
@@ -90,7 +90,7 @@ const dwengoApiLearningObjectProvider: LearningObjectProvider = {
             metadataUrl,
             `Metadata for Learning Object HRUID "${id.hruid}" (language ${id.language})`,
             {
-                params: id,
+                params: { ...id },
             }
         );
 
@@ -123,7 +123,7 @@ const dwengoApiLearningObjectProvider: LearningObjectProvider = {
     async getLearningObjectHTML(id: LearningObjectIdentifier): Promise<string | null> {
         const htmlUrl = `${DWENGO_API_BASE}/learningObject/getRaw`;
         const html = await fetchWithLogging<string>(htmlUrl, `Metadata for Learning Object HRUID "${id.hruid}" (language ${id.language})`, {
-            params: id,
+            params: { ...id },
         });
 
         if (!html) {
diff --git a/backend/src/services/learning-objects/learning-object-provider.ts b/backend/src/services/learning-objects/learning-object-provider.ts
index 81b4d228..6ea7cbd1 100644
--- a/backend/src/services/learning-objects/learning-object-provider.ts
+++ b/backend/src/services/learning-objects/learning-object-provider.ts
@@ -1,4 +1,4 @@
-import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '../../interfaces/learning-content.js';
+import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from 'dwengo-1-common/src/interfaces/learning-content';
 
 export interface LearningObjectProvider {
     /**
diff --git a/backend/src/services/learning-objects/learning-object-service.ts b/backend/src/services/learning-objects/learning-object-service.ts
index 59ffb643..7a4dd828 100644
--- a/backend/src/services/learning-objects/learning-object-service.ts
+++ b/backend/src/services/learning-objects/learning-object-service.ts
@@ -1,8 +1,8 @@
-import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '../../interfaces/learning-content.js';
 import dwengoApiLearningObjectProvider from './dwengo-api-learning-object-provider.js';
 import { LearningObjectProvider } from './learning-object-provider.js';
 import { envVars, getEnvVar } from '../../util/envVars.js';
 import databaseLearningObjectProvider from './database-learning-object-provider.js';
+import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from 'dwengo-1-common/src/interfaces/learning-content';
 
 function getProvider(id: LearningObjectIdentifier): LearningObjectProvider {
     if (id.hruid.startsWith(getEnvVar(envVars.UserContentPrefix))) {
diff --git a/backend/src/services/learning-objects/processing/markdown/dwengo-marked-renderer.ts b/backend/src/services/learning-objects/processing/markdown/dwengo-marked-renderer.ts
index d1c797be..3b9ad4e5 100644
--- a/backend/src/services/learning-objects/processing/markdown/dwengo-marked-renderer.ts
+++ b/backend/src/services/learning-objects/processing/markdown/dwengo-marked-renderer.ts
@@ -8,13 +8,13 @@ import InlineImageProcessor from '../image/inline-image-processor.js';
 import * as marked from 'marked';
 import { getUrlStringForLearningObjectHTML, isValidHttpUrl } from '../../../../util/links.js';
 import { ProcessingError } from '../processing-error.js';
-import { LearningObjectIdentifier } from '../../../../interfaces/learning-content.js';
 import { Language } from '../../../../entities/content/language.js';
 
 import Image = marked.Tokens.Image;
 import Heading = marked.Tokens.Heading;
 import Link = marked.Tokens.Link;
 import RendererObject = marked.RendererObject;
+import { LearningObjectIdentifier } from 'dwengo-1-common/src/interfaces/learning-content';
 
 const prefixes = {
     learningObject: '@learning-object',
diff --git a/backend/src/services/learning-objects/processing/processing-service.ts b/backend/src/services/learning-objects/processing/processing-service.ts
index f731eb5d..d0d43061 100644
--- a/backend/src/services/learning-objects/processing/processing-service.ts
+++ b/backend/src/services/learning-objects/processing/processing-service.ts
@@ -13,9 +13,9 @@ import GiftProcessor from './gift/gift-processor.js';
 import { LearningObject } from '../../../entities/content/learning-object.entity.js';
 import Processor from './processor.js';
 import { DwengoContentType } from './content-type.js';
-import { LearningObjectIdentifier } from '../../../interfaces/learning-content.js';
 import { Language } from '../../../entities/content/language.js';
 import { replaceAsync } from '../../../util/async.js';
+import { LearningObjectIdentifier } from 'dwengo-1-common/src/interfaces/learning-content';
 
 const EMBEDDED_LEARNING_OBJECT_PLACEHOLDER = /<learning-object hruid="([^"]+)" language="([^"]+)" version="([^"]+)"\/>/g;
 const LEARNING_OBJECT_DOES_NOT_EXIST = "<div class='non-existing-learning-object' />";
diff --git a/backend/src/services/learning-paths/database-learning-path-provider.ts b/backend/src/services/learning-paths/database-learning-path-provider.ts
index 3d883ef2..d0fcf630 100644
--- a/backend/src/services/learning-paths/database-learning-path-provider.ts
+++ b/backend/src/services/learning-paths/database-learning-path-provider.ts
@@ -1,5 +1,4 @@
 import { LearningPathProvider } from './learning-path-provider.js';
-import { FilteredLearningObject, LearningObjectNode, LearningPath, LearningPathResponse, Transition } from '../../interfaces/learning-content.js';
 import { LearningPath as LearningPathEntity } from '../../entities/content/learning-path.entity.js';
 import { getLearningPathRepository } from '../../data/repositories.js';
 import { Language } from '../../entities/content/language.js';
@@ -7,6 +6,13 @@ import learningObjectService from '../learning-objects/learning-object-service.j
 import { LearningPathNode } from '../../entities/content/learning-path-node.entity.js';
 import { LearningPathTransition } from '../../entities/content/learning-path-transition.entity.js';
 import { getLastSubmissionForCustomizationTarget, isTransitionPossible, PersonalizationTarget } from './learning-path-personalization-util.js';
+import {
+    FilteredLearningObject,
+    LearningObjectNode,
+    LearningPath,
+    LearningPathResponse,
+    Transition,
+} from 'dwengo-1-common/src/interfaces/learning-content';
 
 /**
  * Fetches the corresponding learning object for each of the nodes and creates a map that maps each node to its
diff --git a/backend/src/services/learning-paths/dwengo-api-learning-path-provider.ts b/backend/src/services/learning-paths/dwengo-api-learning-path-provider.ts
index a6093bb4..b7f03d35 100644
--- a/backend/src/services/learning-paths/dwengo-api-learning-path-provider.ts
+++ b/backend/src/services/learning-paths/dwengo-api-learning-path-provider.ts
@@ -1,8 +1,8 @@
 import { fetchWithLogging } from '../../util/api-helper.js';
 import { DWENGO_API_BASE } from '../../config.js';
-import { LearningPath, LearningPathResponse } from '../../interfaces/learning-content.js';
 import { LearningPathProvider } from './learning-path-provider.js';
 import { getLogger, Logger } from '../../logging/initalize.js';
+import { LearningPath, LearningPathResponse } from 'dwengo-1-common/src/interfaces/learning-content';
 
 const logger: Logger = getLogger();
 
diff --git a/backend/src/services/learning-paths/learning-path-provider.ts b/backend/src/services/learning-paths/learning-path-provider.ts
index 5e2a09df..a904296a 100644
--- a/backend/src/services/learning-paths/learning-path-provider.ts
+++ b/backend/src/services/learning-paths/learning-path-provider.ts
@@ -1,6 +1,6 @@
-import { LearningPath, LearningPathResponse } from '../../interfaces/learning-content.js';
 import { Language } from '../../entities/content/language.js';
 import { PersonalizationTarget } from './learning-path-personalization-util.js';
+import { LearningPath, LearningPathResponse } from 'dwengo-1-common/src/interfaces/learning-content';
 
 /**
  * Generic interface for a service which provides access to learning paths from a data source.
diff --git a/backend/src/services/learning-paths/learning-path-service.ts b/backend/src/services/learning-paths/learning-path-service.ts
index f8e328b2..bebfe8a9 100644
--- a/backend/src/services/learning-paths/learning-path-service.ts
+++ b/backend/src/services/learning-paths/learning-path-service.ts
@@ -1,9 +1,9 @@
-import { LearningPath, LearningPathResponse } from '../../interfaces/learning-content.js';
 import dwengoApiLearningPathProvider from './dwengo-api-learning-path-provider.js';
 import databaseLearningPathProvider from './database-learning-path-provider.js';
 import { envVars, getEnvVar } from '../../util/envVars.js';
 import { Language } from '../../entities/content/language.js';
 import { PersonalizationTarget } from './learning-path-personalization-util.js';
+import { LearningPath, LearningPathResponse } from 'dwengo-1-common/src/interfaces/learning-content';
 
 const userContentPrefix = getEnvVar(envVars.UserContentPrefix);
 const allProviders = [dwengoApiLearningPathProvider, databaseLearningPathProvider];
diff --git a/backend/src/services/submissions.ts b/backend/src/services/submissions.ts
index a456d9d1..314b9d65 100644
--- a/backend/src/services/submissions.ts
+++ b/backend/src/services/submissions.ts
@@ -1,7 +1,8 @@
 import { getSubmissionRepository } from '../data/repositories.js';
 import { Language } from '../entities/content/language.js';
 import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
-import { mapToSubmission, mapToSubmissionDTO, SubmissionDTO } from '../interfaces/submission.js';
+import { mapToSubmission, mapToSubmissionDTO } from '../interfaces/submission.js';
+import { SubmissionDTO } from 'dwengo-1-common/src/interfaces/submission';
 
 export async function getSubmission(
     learningObjectHruid: string,
diff --git a/backend/src/util/api-helper.ts b/backend/src/util/api-helper.ts
index 9aac5bd1..af36532d 100644
--- a/backend/src/util/api-helper.ts
+++ b/backend/src/util/api-helper.ts
@@ -1,6 +1,6 @@
 import axios, { AxiosRequestConfig } from 'axios';
 import { getLogger, Logger } from '../logging/initalize.js';
-import { LearningObjectIdentifier } from '../interfaces/learning-content.js';
+import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
 
 const logger: Logger = getLogger();
 
diff --git a/backend/src/util/links.ts b/backend/src/util/links.ts
index ff334eb5..bd14bfba 100644
--- a/backend/src/util/links.ts
+++ b/backend/src/util/links.ts
@@ -1,4 +1,4 @@
-import { LearningObjectIdentifier } from '../interfaces/learning-content';
+import { LearningObjectIdentifier } from 'dwengo-1-common/src/interfaces/learning-content';
 
 export function isValidHttpUrl(url: string): boolean {
     try {
diff --git a/backend/tests/services/learning-objects/database-learning-object-provider.test.ts b/backend/tests/services/learning-objects/database-learning-object-provider.test.ts
index 2c3b7dfc..e87c158b 100644
--- a/backend/tests/services/learning-objects/database-learning-object-provider.test.ts
+++ b/backend/tests/services/learning-objects/database-learning-object-provider.test.ts
@@ -5,11 +5,11 @@ import example from '../../test-assets/learning-objects/pn-werkingnotebooks/pn-w
 import { LearningObject } from '../../../src/entities/content/learning-object.entity';
 import databaseLearningObjectProvider from '../../../src/services/learning-objects/database-learning-object-provider';
 import { expectToBeCorrectFilteredLearningObject } from '../../test-utils/expectations';
-import { FilteredLearningObject } from '../../../src/interfaces/learning-content';
 import { Language } from '../../../src/entities/content/language';
 import learningObjectExample from '../../test-assets/learning-objects/pn-werkingnotebooks/pn-werkingnotebooks-example';
 import learningPathExample from '../../test-assets/learning-paths/pn-werking-example';
 import { LearningPath } from '../../../src/entities/content/learning-path.entity';
+import { FilteredLearningObject } from 'dwengo-1-common/src/interfaces/learning-content';
 
 async function initExampleData(): Promise<{ learningObject: LearningObject; learningPath: LearningPath }> {
     const learningObjectRepo = getLearningObjectRepository();
diff --git a/backend/tests/services/learning-objects/learning-object-service.test.ts b/backend/tests/services/learning-objects/learning-object-service.test.ts
index f284b939..2e96c4fc 100644
--- a/backend/tests/services/learning-objects/learning-object-service.test.ts
+++ b/backend/tests/services/learning-objects/learning-object-service.test.ts
@@ -4,11 +4,11 @@ import { LearningObject } from '../../../src/entities/content/learning-object.en
 import { getLearningObjectRepository, getLearningPathRepository } from '../../../src/data/repositories';
 import learningObjectExample from '../../test-assets/learning-objects/pn-werkingnotebooks/pn-werkingnotebooks-example';
 import learningObjectService from '../../../src/services/learning-objects/learning-object-service';
-import { LearningObjectIdentifier, LearningPathIdentifier } from '../../../src/interfaces/learning-content';
 import { Language } from '../../../src/entities/content/language';
 import { envVars, getEnvVar } from '../../../src/util/envVars';
 import { LearningPath } from '../../../src/entities/content/learning-path.entity';
 import learningPathExample from '../../test-assets/learning-paths/pn-werking-example';
+import { LearningObjectIdentifier, LearningPathIdentifier } from 'dwengo-1-common/src/interfaces/learning-content';
 
 const EXPECTED_DWENGO_LEARNING_OBJECT_TITLE = 'Werken met notebooks';
 const DWENGO_TEST_LEARNING_OBJECT_ID: LearningObjectIdentifier = {
@@ -105,7 +105,10 @@ describe('LearningObjectService', () => {
             expect(new Set(result.map((it) => it.key))).toEqual(DWENGO_TEST_LEARNING_PATH_HRUIDS);
         });
         it('returns an empty list when queried with a non-existing learning path id', async () => {
-            const result = await learningObjectService.getLearningObjectsFromPath({ hruid: 'non_existing', language: Language.Dutch });
+            const result = await learningObjectService.getLearningObjectsFromPath({
+                hruid: 'non_existing',
+                language: Language.Dutch,
+            });
             expect(result).toEqual([]);
         });
     });
@@ -120,7 +123,10 @@ describe('LearningObjectService', () => {
             expect(new Set(result)).toEqual(DWENGO_TEST_LEARNING_PATH_HRUIDS);
         });
         it('returns an empty list when queried with a non-existing learning path id', async () => {
-            const result = await learningObjectService.getLearningObjectIdsFromPath({ hruid: 'non_existing', language: Language.Dutch });
+            const result = await learningObjectService.getLearningObjectIdsFromPath({
+                hruid: 'non_existing',
+                language: Language.Dutch,
+            });
             expect(result).toEqual([]);
         });
     });
diff --git a/backend/tests/services/learning-path/database-learning-path-provider.test.ts b/backend/tests/services/learning-path/database-learning-path-provider.test.ts
index a5943f5f..7b1f2bf8 100644
--- a/backend/tests/services/learning-path/database-learning-path-provider.test.ts
+++ b/backend/tests/services/learning-path/database-learning-path-provider.test.ts
@@ -19,7 +19,8 @@ import {
     createConditionTestLearningPathAndLearningObjects,
 } from '../../test-assets/learning-paths/test-conditions-example.js';
 import { Student } from '../../../src/entities/users/student.entity.js';
-import { LearningObjectNode, LearningPathResponse } from '../../../src/interfaces/learning-content.js';
+
+import { LearningObjectNode, LearningPathResponse } from 'dwengo-1-common/src/interfaces/learning-content';
 
 async function initExampleData(): Promise<{ learningObject: LearningObject; learningPath: LearningPath }> {
     const learningObjectRepo = getLearningObjectRepository();
diff --git a/backend/tests/test-utils/expectations.ts b/backend/tests/test-utils/expectations.ts
index c3fa5a43..374bf6a7 100644
--- a/backend/tests/test-utils/expectations.ts
+++ b/backend/tests/test-utils/expectations.ts
@@ -1,8 +1,8 @@
 import { AssertionError } from 'node:assert';
 import { LearningObject } from '../../src/entities/content/learning-object.entity';
-import { FilteredLearningObject, LearningPath } from '../../src/interfaces/learning-content';
 import { LearningPath as LearningPathEntity } from '../../src/entities/content/learning-path.entity';
 import { expect } from 'vitest';
+import { FilteredLearningObject, LearningPath } from 'dwengo-1-common/src/interfaces/learning-content';
 
 // Ignored properties because they belang for example to the class, not to the entity itself.
 const IGNORE_PROPERTIES = ['parent'];
diff --git a/backend/tsconfig.json b/backend/tsconfig.json
index 2dd3998d..a47827ba 100644
--- a/backend/tsconfig.json
+++ b/backend/tsconfig.json
@@ -4,6 +4,8 @@
     "compilerOptions": {
         "rootDir": "./src",
         "outDir": "./dist",
-        "resolveJsonModule": true
+        "resolveJsonModule": true,
+        "sourceMap": true,
+        "composite": true
     }
 }
diff --git a/common/package.json b/common/package.json
new file mode 100644
index 00000000..db8adfd0
--- /dev/null
+++ b/common/package.json
@@ -0,0 +1,16 @@
+{
+    "name": "dwengo-1-common",
+    "version": "0.1.1",
+    "description": "Common types and utilities for Dwengo-1",
+    "private": true,
+    "type": "module",
+    "scripts": {
+        "build": "tsc --project tsconfig.json",
+        "format": "prettier --write src/",
+        "format-check": "prettier --check src/",
+        "lint": "eslint . --fix"
+    },
+    "exports": {
+        "./src/*": "./dist/*"
+    }
+}
diff --git a/common/src/interfaces/answer.d.ts b/common/src/interfaces/answer.d.ts
new file mode 100644
index 00000000..d2faf87d
--- /dev/null
+++ b/common/src/interfaces/answer.d.ts
@@ -0,0 +1,16 @@
+import { UserDTO } from './user';
+import { QuestionDTO } from './question';
+
+export interface AnswerDTO {
+    author: UserDTO;
+    toQuestion: QuestionDTO;
+    sequenceNumber: number;
+    timestamp: string;
+    content: string;
+}
+
+export interface AnswerId {
+    author: string;
+    toQuestion: QuestionId;
+    sequenceNumber: number;
+}
diff --git a/common/src/interfaces/assignment.d.ts b/common/src/interfaces/assignment.d.ts
new file mode 100644
index 00000000..8ad1649b
--- /dev/null
+++ b/common/src/interfaces/assignment.d.ts
@@ -0,0 +1,11 @@
+import { GroupDTO } from './group';
+
+export interface AssignmentDTO {
+    id: number;
+    class: string; // Id of class 'within'
+    title: string;
+    description: string;
+    learningPath: string;
+    language: string;
+    groups?: GroupDTO[] | string[]; // TODO
+}
diff --git a/common/src/interfaces/class.d.ts b/common/src/interfaces/class.d.ts
new file mode 100644
index 00000000..c35c2dfc
--- /dev/null
+++ b/common/src/interfaces/class.d.ts
@@ -0,0 +1,7 @@
+export interface ClassDTO {
+    id: string;
+    displayName: string;
+    teachers: string[];
+    students: string[];
+    joinRequests: string[];
+}
diff --git a/common/src/interfaces/group.d.ts b/common/src/interfaces/group.d.ts
new file mode 100644
index 00000000..45523461
--- /dev/null
+++ b/common/src/interfaces/group.d.ts
@@ -0,0 +1,7 @@
+import { AssignmentDTO } from './assignment';
+
+export interface GroupDTO {
+    assignment: number | AssignmentDTO;
+    groupNumber: number;
+    members: string[] | StudentDTO[];
+}
diff --git a/backend/src/interfaces/learning-content.ts b/common/src/interfaces/learning-content.d.ts
similarity index 96%
rename from backend/src/interfaces/learning-content.ts
rename to common/src/interfaces/learning-content.d.ts
index 693aec37..610b1385 100644
--- a/backend/src/interfaces/learning-content.ts
+++ b/common/src/interfaces/learning-content.d.ts
@@ -1,4 +1,4 @@
-import { Language } from '../entities/content/language';
+import { Language } from 'dwengo-1-backend/src/entities/content/language.js';
 
 export interface Transition {
     default: boolean;
diff --git a/common/src/interfaces/question.d.ts b/common/src/interfaces/question.d.ts
new file mode 100644
index 00000000..2b2a263c
--- /dev/null
+++ b/common/src/interfaces/question.d.ts
@@ -0,0 +1,14 @@
+import { StudentDTO } from './student';
+
+export interface QuestionDTO {
+    learningObjectIdentifier: LearningObjectIdentifier;
+    sequenceNumber?: number;
+    author: StudentDTO;
+    timestamp?: string;
+    content: string;
+}
+
+export interface QuestionId {
+    learningObjectIdentifier: LearningObjectIdentifier;
+    sequenceNumber: number;
+}
diff --git a/common/src/interfaces/student.d.ts b/common/src/interfaces/student.d.ts
new file mode 100644
index 00000000..cb13d3c2
--- /dev/null
+++ b/common/src/interfaces/student.d.ts
@@ -0,0 +1,12 @@
+export interface StudentDTO {
+    id: string;
+    username: string;
+    firstName: string;
+    lastName: string;
+    endpoints?: {
+        classes: string;
+        questions: string;
+        invitations: string;
+        groups: string;
+    };
+}
diff --git a/common/src/interfaces/submission.d.ts b/common/src/interfaces/submission.d.ts
new file mode 100644
index 00000000..c4c2b35d
--- /dev/null
+++ b/common/src/interfaces/submission.d.ts
@@ -0,0 +1,19 @@
+import { GroupDTO } from './group';
+
+export interface SubmissionDTO {
+    learningObjectIdentifier: LearningObjectIdentifier;
+
+    submissionNumber?: number;
+    submitter: StudentDTO;
+    time?: Date;
+    group?: GroupDTO;
+    content: string;
+}
+
+export interface SubmissionDTOId {
+    learningObjectHruid: string;
+    learningObjectLanguage: Language;
+    learningObjectVersion: number;
+
+    submissionNumber?: number;
+}
diff --git a/common/src/interfaces/teacher-invitation.d.ts b/common/src/interfaces/teacher-invitation.d.ts
new file mode 100644
index 00000000..13709322
--- /dev/null
+++ b/common/src/interfaces/teacher-invitation.d.ts
@@ -0,0 +1,8 @@
+import { UserDTO } from './user';
+import { ClassDTO } from './class';
+
+export interface TeacherInvitationDTO {
+    sender: string | UserDTO;
+    receiver: string | UserDTO;
+    class: string | ClassDTO;
+}
diff --git a/common/src/interfaces/teacher.d.ts b/common/src/interfaces/teacher.d.ts
new file mode 100644
index 00000000..05bf74a0
--- /dev/null
+++ b/common/src/interfaces/teacher.d.ts
@@ -0,0 +1,12 @@
+export interface TeacherDTO {
+    id: string;
+    username: string;
+    firstName: string;
+    lastName: string;
+    endpoints?: {
+        classes: string;
+        questions: string;
+        invitations: string;
+        groups: string;
+    };
+}
diff --git a/common/src/interfaces/user.d.ts b/common/src/interfaces/user.d.ts
new file mode 100644
index 00000000..e7bbe2ed
--- /dev/null
+++ b/common/src/interfaces/user.d.ts
@@ -0,0 +1,12 @@
+export interface UserDTO {
+    id?: string;
+    username: string;
+    firstName: string;
+    lastName: string;
+    endpoints?: {
+        self: string;
+        classes: string;
+        questions: string;
+        invitations: string;
+    };
+}
diff --git a/common/tsconfig.json b/common/tsconfig.json
new file mode 100644
index 00000000..a47827ba
--- /dev/null
+++ b/common/tsconfig.json
@@ -0,0 +1,11 @@
+{
+    "extends": "../tsconfig.json",
+    "include": ["src/**/*.ts"],
+    "compilerOptions": {
+        "rootDir": "./src",
+        "outDir": "./dist",
+        "resolveJsonModule": true,
+        "sourceMap": true,
+        "composite": true
+    }
+}
diff --git a/package-lock.json b/package-lock.json
index a38ca88a..52338b8a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -10,6 +10,7 @@
             "license": "MIT",
             "workspaces": [
                 "backend",
+                "common",
                 "frontend",
                 "docs"
             ],
@@ -40,6 +41,7 @@
                 "cross": "^1.0.0",
                 "cross-env": "^7.0.3",
                 "dotenv": "^16.4.7",
+                "dwengo-1-common": "^0.1.1",
                 "express": "^5.0.1",
                 "express-jwt": "^8.5.1",
                 "gift-pegjs": "^1.0.2",
@@ -83,6 +85,10 @@
                 "url": "https://github.com/sponsors/sindresorhus"
             }
         },
+        "common": {
+            "name": "dwengo-1-common",
+            "version": "0.1.1"
+        },
         "docs": {
             "name": "dwengo-1-docs",
             "version": "0.0.1",
@@ -4919,6 +4925,10 @@
             "resolved": "backend",
             "link": true
         },
+        "node_modules/dwengo-1-common": {
+            "resolved": "common",
+            "link": true
+        },
         "node_modules/dwengo-1-docs": {
             "resolved": "docs",
             "link": true
diff --git a/package.json b/package.json
index e23a49f6..c7eeccc3 100644
--- a/package.json
+++ b/package.json
@@ -5,14 +5,15 @@
     "private": true,
     "type": "module",
     "scripts": {
-        "build": "npm run build --workspace=backend --workspace=frontend",
-        "format": "npm run format --workspace=backend --workspace=frontend",
-        "format-check": "npm run format-check --workspace=backend --workspace=frontend",
-        "lint": "npm run lint --workspace=backend --workspace=frontend",
+        "build": "npm run build --workspaces --if-present",
+        "format": "npm run format --workspace=backend --workspace=common --workspace=frontend",
+        "format-check": "npm run format-check --workspace=backend --workspace=common --workspace=frontend",
+        "lint": "npm run lint --workspace=backend --workspace=common --workspace=frontend",
         "test:unit": "npm run test:unit --workspace=backend --workspace=frontend"
     },
     "workspaces": [
         "backend",
+        "common",
         "frontend",
         "docs"
     ],