diff --git a/backend/src/database/DatabaseInterface.ts b/backend/src/database/DatabaseInterface.ts
index 476f9b0..5e85c49 100644
--- a/backend/src/database/DatabaseInterface.ts
+++ b/backend/src/database/DatabaseInterface.ts
@@ -121,6 +121,7 @@ export interface DBGlobalBlock {
   name: string;
   block_data: string;
   svg_data: string | null;
+  is_favorite: boolean;
   created_at: string;
   updated_at: string;
 }
diff --git a/backend/src/database/SqliteAdapter.ts b/backend/src/database/SqliteAdapter.ts
index e85efb8..f19a17f 100644
--- a/backend/src/database/SqliteAdapter.ts
+++ b/backend/src/database/SqliteAdapter.ts
@@ -35,6 +35,11 @@ export class SqliteAdapter implements DatabaseInterface {
     if (!columns.some(col => col.name === 'folder_id')) {
       this.db.exec('ALTER TABLE projects ADD COLUMN folder_id TEXT REFERENCES project_folders(id) ON DELETE SET NULL');
     }
+    // Add is_favorite column to global_blocks table for existing databases (Task F2)
+    const gbColumns = this.db.prepare("PRAGMA table_info('global_blocks')").all() as { name: string }[];
+    if (!gbColumns.some(col => col.name === 'is_favorite')) {
+      this.db.exec('ALTER TABLE global_blocks ADD COLUMN is_favorite INTEGER NOT NULL DEFAULT 0');
+    }
   }
 
   close(): void {
@@ -423,25 +428,31 @@ export class SqliteAdapter implements DatabaseInterface {
   }
 
   // ─── Global Blocks ─────────────────────────────────────
+  // Map DB row to DBGlobalBlock (is_favorite 0/1 → boolean, Task F2)
+  private mapGlobalBlockRow(row: Record<string, unknown>): DBGlobalBlock {
+    return { ...(row as unknown as DBGlobalBlock), is_favorite: Number(row.is_favorite ?? 0) === 1 };
+  }
+
   listGlobalBlocks(folderId?: string | null): DBGlobalBlock[] {
     if (folderId === undefined) {
-      return this.db.prepare('SELECT * FROM global_blocks ORDER BY updated_at DESC').all() as DBGlobalBlock[];
+      return (this.db.prepare('SELECT * FROM global_blocks ORDER BY updated_at DESC').all() as Record<string, unknown>[]).map(r => this.mapGlobalBlockRow(r));
     }
     if (folderId === null) {
-      return this.db.prepare('SELECT * FROM global_blocks WHERE folder_id IS NULL ORDER BY updated_at DESC').all() as DBGlobalBlock[];
+      return (this.db.prepare('SELECT * FROM global_blocks WHERE folder_id IS NULL ORDER BY updated_at DESC').all() as Record<string, unknown>[]).map(r => this.mapGlobalBlockRow(r));
     }
-    return this.db.prepare('SELECT * FROM global_blocks WHERE folder_id = ? ORDER BY updated_at DESC').all(folderId) as DBGlobalBlock[];
+    return (this.db.prepare('SELECT * FROM global_blocks WHERE folder_id = ? ORDER BY updated_at DESC').all(folderId) as Record<string, unknown>[]).map(r => this.mapGlobalBlockRow(r));
   }
 
   getGlobalBlock(id: string): DBGlobalBlock | null {
-    return (this.db.prepare('SELECT * FROM global_blocks WHERE id = ?').get(id) as DBGlobalBlock) ?? null;
+    const row = this.db.prepare('SELECT * FROM global_blocks WHERE id = ?').get(id) as Record<string, unknown> | undefined;
+    return row ? this.mapGlobalBlockRow(row) : null;
   }
 
   createGlobalBlock(data: Partial<DBGlobalBlock>): DBGlobalBlock {
     const id = data.id ?? `gblock-${randomUUID().slice(0, 8)}`;
     this.db.prepare(
-      'INSERT INTO global_blocks (id, folder_id, name, block_data, svg_data) VALUES (?, ?, ?, ?, ?)',
-    ).run(id, data.folder_id ?? null, data.name ?? 'Global Block', data.block_data ?? '{}', data.svg_data ?? null);
+      'INSERT INTO global_blocks (id, folder_id, name, block_data, svg_data, is_favorite) VALUES (?, ?, ?, ?, ?, ?)',
+    ).run(id, data.folder_id ?? null, data.name ?? 'Global Block', data.block_data ?? '{}', data.svg_data ?? null, data.is_favorite ? 1 : 0);
     return this.getGlobalBlock(id)!;
   }
 
@@ -452,6 +463,7 @@ export class SqliteAdapter implements DatabaseInterface {
     if (data.folder_id !== undefined) { sets.push('folder_id = ?'); vals.push(data.folder_id); }
     if (data.block_data !== undefined) { sets.push('block_data = ?'); vals.push(data.block_data); }
     if (data.svg_data !== undefined) { sets.push('svg_data = ?'); vals.push(data.svg_data); }
+    if (data.is_favorite !== undefined) { sets.push('is_favorite = ?'); vals.push(data.is_favorite ? 1 : 0); }
     sets.push("updated_at = datetime('now')");
     this.db.prepare(`UPDATE global_blocks SET ${sets.join(', ')} WHERE id = ?`).run(...vals, id);
     return this.getGlobalBlock(id);
diff --git a/backend/src/database/schema.sql b/backend/src/database/schema.sql
index bb4dd12..dae4b63 100644
--- a/backend/src/database/schema.sql
+++ b/backend/src/database/schema.sql
@@ -171,6 +171,7 @@ CREATE TABLE IF NOT EXISTS global_blocks (
   name TEXT NOT NULL,
   block_data TEXT NOT NULL DEFAULT '{}',
   svg_data TEXT,
+  is_favorite INTEGER NOT NULL DEFAULT 0,
   created_at TEXT NOT NULL DEFAULT (datetime('now')),
   updated_at TEXT NOT NULL DEFAULT (datetime('now')),
   FOREIGN KEY (folder_id) REFERENCES global_block_folders(id) ON DELETE SET NULL
diff --git a/backend/src/routes/globalBlocks.ts b/backend/src/routes/globalBlocks.ts
index 0cebe5c..000253c 100644
--- a/backend/src/routes/globalBlocks.ts
+++ b/backend/src/routes/globalBlocks.ts
@@ -134,11 +134,14 @@ export function registerGlobalBlockRoutes(fastify: FastifyInstance, db: Database
     const { id } = request.params as { id: string };
     const idErr = validateIdParam(id, 'id');
     if (idErr) return reply.code(400).send({ error: idErr });
-    const body = request.body as { name?: string; folder_id?: string | null; block_data?: string; svg_data?: string };
+    const body = request.body as { name?: string; folder_id?: string | null; block_data?: string; svg_data?: string; is_favorite?: boolean };
     if (body.name !== undefined) {
       const nameErr = validateName(body.name, 'name');
       if (nameErr) return reply.code(400).send({ error: nameErr });
     }
+    if (body.is_favorite !== undefined && typeof body.is_favorite !== 'boolean') {
+      return reply.code(400).send({ error: 'is_favorite must be a boolean' });
+    }
     if (body.folder_id !== undefined && body.folder_id !== null) {
       const fidErr = validateIdParam(body.folder_id, 'folder_id');
       if (fidErr) return reply.code(400).send({ error: fidErr });
diff --git a/backend/tests/globalBlocks.test.ts b/backend/tests/globalBlocks.test.ts
index cafad0b..209a916 100644
--- a/backend/tests/globalBlocks.test.ts
+++ b/backend/tests/globalBlocks.test.ts
@@ -525,3 +525,90 @@ describe('Global Blocks API – F1 export/import', () => {
     expect(res.statusCode).toBe(400);
   });
 });
+
+// ─── Task F2: Block-Favoriten ─────────────────────────────
+describe('Global Blocks API – F2 favorite', () => {
+  let app: FastifyInstance;
+  let db: SqliteAdapter;
+  let authToken: string;
+  let blockId: string;
+
+  beforeAll(async () => {
+    db = new SqliteAdapter(':memory:');
+    await db.init();
+    app = await createServer({ db, port: 0 });
+    await app.ready();
+
+    const regRes = await app.inject({
+      method: 'POST',
+      url: '/api/auth/register',
+      payload: { email: 'fav-test@example.com', password: 'Password123!', name: 'Fav Test', role: 'admin' },
+    });
+    authToken = JSON.parse(regRes.body).session.token;
+
+    const blockRes = await app.inject({
+      method: 'POST',
+      url: '/api/global-blocks',
+      headers: { authorization: `Bearer ${authToken}` },
+      payload: { name: 'Fav-Block', block_data: '{"type":"block"}' },
+    });
+    blockId = JSON.parse(blockRes.body).id;
+  });
+
+  afterAll(async () => {
+    await app.close();
+    db.close();
+  });
+
+  it('neuer Block startet mit is_favorite=false', async () => {
+    const res = await app.inject({
+      method: 'GET',
+      url: `/api/global-blocks/${blockId}`,
+      headers: { authorization: `Bearer ${authToken}` },
+    });
+    expect(res.statusCode).toBe(200);
+    expect(JSON.parse(res.body).is_favorite).toBe(false);
+  });
+
+  it('PATCH is_favorite:true setzt Favorit', async () => {
+    const res = await app.inject({
+      method: 'PATCH',
+      url: `/api/global-blocks/${blockId}`,
+      headers: { authorization: `Bearer ${authToken}` },
+      payload: { is_favorite: true },
+    });
+    expect(res.statusCode).toBe(200);
+    expect(JSON.parse(res.body).is_favorite).toBe(true);
+  });
+
+  it('is_favorite ist persistent nach GET', async () => {
+    const res = await app.inject({
+      method: 'GET',
+      url: `/api/global-blocks/${blockId}`,
+      headers: { authorization: `Bearer ${authToken}` },
+    });
+    expect(res.statusCode).toBe(200);
+    expect(JSON.parse(res.body).is_favorite).toBe(true);
+  });
+
+  it('PATCH is_favorite:false hebt Favorit auf', async () => {
+    const res = await app.inject({
+      method: 'PATCH',
+      url: `/api/global-blocks/${blockId}`,
+      headers: { authorization: `Bearer ${authToken}` },
+      payload: { is_favorite: false },
+    });
+    expect(res.statusCode).toBe(200);
+    expect(JSON.parse(res.body).is_favorite).toBe(false);
+  });
+
+  it('PATCH mit nicht-boolean is_favorite liefert 400', async () => {
+    const res = await app.inject({
+      method: 'PATCH',
+      url: `/api/global-blocks/${blockId}`,
+      headers: { authorization: `Bearer ${authToken}` },
+      payload: { is_favorite: 'yes' },
+    });
+    expect(res.statusCode).toBe(400);
+  });
+});