diff --git a/src/backend/services/fs/FSService.ts b/src/backend/services/fs/FSService.ts
index 2d849ec1d..548739514 100644
--- a/src/backend/services/fs/FSService.ts
+++ b/src/backend/services/fs/FSService.ts
@@ -170,6 +170,9 @@ const isAppDataRootPath = (path: string): boolean => {
     );
 };
 
+/** Ends a subtree removal whose `proceed` check said to stop. */
+class RemovalStopped extends Error {}
+
 const isNoSuchKeyError = (err: unknown): boolean => {
     if (!err || typeof err !== 'object') return false;
     const e = err as { name?: unknown; Code?: unknown };
@@ -311,6 +314,10 @@ export class FSService extends PuterService {
 
     override onServerStart(): void {
         this.#registerPermissionRules();
+        this.clients.event.on('app.uninstalled', async (_key, data) => {
+            if (!data?.deleteData) return;
+            void this.#removeUninstalledAppData(data.userId, data.appUid);
+        });
     }
 
     /**
@@ -4565,27 +4572,111 @@ export class FSService extends PuterService {
     /**
      * Delete a directory's contents a page at a time, leaves first, so neither
      * memory nor a single statement grows with the subtree: a page's files go
-     * as it is read, a directory once everything under it has.
+     * as it is read, a directory once everything under it has. With `proceed`,
+     * each batch is deleted only while it answers true; false if it stopped.
      */
     async #removeDescendants(
         root: FSEntry,
         survivors: () => Promise<AncestorChain>,
-    ): Promise<void> {
+        proceed?: () => Promise<boolean>,
+    ): Promise<boolean> {
         const removeEntries = async (entries: FSEntry[]) => {
             if (entries.length === 0) return;
+            if (proceed && !(await proceed())) throw new RemovalStopped();
             // S3 objects are batched per bucket+region.
             await this.#removeDescendantsStorage(entries);
             await this.stores.fsEntry.deleteEntries(entries);
             this.#emitRemoveEvents(entries, survivors);
         };
-        await this.#walkSubtree(
-            root,
-            async (page) => {
-                await removeEntries(page.filter((entry) => !entry.isDir));
-                return page.filter((entry) => entry.isDir);
-            },
-            removeEntries,
-        );
+        try {
+            await this.#walkSubtree(
+                root,
+                async (page) => {
+                    await removeEntries(page.filter((entry) => !entry.isDir));
+                    return page.filter((entry) => entry.isDir);
+                },
+                removeEntries,
+            );
+        } catch (err) {
+            if (err instanceof RemovalStopped) return false;
+            throw err;
+        }
+        return true;
+    }
+
+    /**
+     * Delete `/<user>/AppData/<app-uid>` once the user removed the app with its
+     * data. Stops if the user authorizes the app again, so files written after
+     * that are kept. A failure is logged, not retried.
+     */
+    async #removeUninstalledAppData(
+        userId: number,
+        appUid: string,
+    ): Promise<void> {
+        if (!userId || !appUid || ['.', '..'].includes(appUid)) return;
+        if (appUid.includes('/')) return;
+        try {
+            const username = (await this.stores.user.getById(userId))?.username;
+            if (!username) return;
+            const path = `/${username}/AppData/${appUid}`;
+            const root = await this.stores.fsEntry.getEntryByPath(path, {
+                lineage: false,
+                skipCache: true,
+            });
+            // The path column's collation also matches other spellings.
+            if (!root?.isDir || root.path !== path || root.userId !== userId)
+                return;
+            if (await this.#subtreeHostsContent(root)) {
+                console.warn(
+                    `[fs] kept uninstalled app data at ${path}: it hosts a site or worker`,
+                );
+                return;
+            }
+
+            const appId = (await this.stores.app.getByUid(appUid))?.id;
+            const stillUninstalled = async () =>
+                typeof appId !== 'number' ||
+                (
+                    await this.stores.permission.listUserAppPermsFromPrimary(
+                        userId,
+                        appId,
+                    )
+                ).length === 0;
+            if (!(await stillUninstalled())) return;
+
+            const survivors = this.#memoizedChain(pathPosix.dirname(path));
+            const emptied = await this.#removeDescendants(
+                root,
+                survivors,
+                stillUninstalled,
+            );
+            if (!emptied || !(await stillUninstalled())) return;
+            await this.stores.fsEntry.deleteEntry(root);
+            this.#emitRemoveEvents([root], survivors);
+        } catch (err) {
+            console.warn('[fs] uninstalled app data removal failed', err);
+        }
+    }
+
+    /** Whether a site or worker is rooted at `root` or anywhere below it. */
+    async #subtreeHostsContent(root: FSEntry): Promise<boolean> {
+        const hosts = (entry: FSEntry) =>
+            entry.subdomains.length > 0 || entry.workers.length > 0;
+        if (hosts(root)) return true;
+        try {
+            await this.#walkSubtree(
+                root,
+                async (page) => {
+                    if (page.some(hosts)) throw new RemovalStopped();
+                    return page.filter((entry) => entry.isDir);
+                },
+                async () => {},
+            );
+        } catch (err) {
+            if (err instanceof RemovalStopped) return true;
+            throw err;
+        }
+        return false;
     }
 
     /**
diff --git a/src/backend/services/fs/FSService.uninstallAppData.test.ts b/src/backend/services/fs/FSService.uninstallAppData.test.ts
new file mode 100644
index 000000000..4b04413c0
--- /dev/null
+++ b/src/backend/services/fs/FSService.uninstallAppData.test.ts
@@ -0,0 +1,234 @@
+/*
+ * Copyright (C) 2024-present Puter Technologies Inc.
+ *
+ * This file is part of Puter.
+ *
+ * Puter is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import {
+    afterAll,
+    afterEach,
+    beforeAll,
+    describe,
+    expect,
+    it,
+    vi,
+} from 'vitest';
+import { setupPuterTestEnv, type PuterTestEnv } from '../../testUtil.js';
+import { FSService } from './FSService.js';
+
+/** Removing an app "with its data" takes its AppData folder too. */
+describe('uninstalling an app with its data', () => {
+    let env: PuterTestEnv;
+    const pageSize = FSService.SUBTREE_PAGE_SIZE;
+
+    beforeAll(async () => {
+        env = await setupPuterTestEnv();
+    }, 120_000);
+
+    afterAll(async () => {
+        await env?.shutdown();
+    });
+
+    afterEach(() => {
+        FSService.SUBTREE_PAGE_SIZE = pageSize;
+        vi.restoreAllMocks();
+    });
+
+    const post = (path: string, token: string, body: unknown) =>
+        fetch(new URL(path, env.apiOrigin), {
+            method: 'POST',
+            headers: {
+                authorization: `Bearer ${token}`,
+                'content-type': 'application/json',
+            },
+            body: JSON.stringify(body),
+        });
+
+    const exists = async (path: string) =>
+        (await env.server.stores.fsEntry.getEntryByPath(path, {
+            skipCache: true,
+        })) !== null;
+
+    const launch = async (origin: string) => {
+        const launched = await post(
+            '/auth/get-user-app-token',
+            env.users.user.token,
+            { origin },
+        );
+        expect(launched.status).toBe(200);
+        return (await launched.json()) as { token: string; app_uid: string };
+    };
+
+    /**
+     * An app with `count` files in its AppData, plus a folder whose name
+     * extends its uid.
+     */
+    const installWithFiles = async (count: number) => {
+        const { username, token } = env.users.user;
+        const origin = `https://uninstall-${Math.random().toString(36).slice(2, 10)}.example.com`;
+        const app = await launch(origin);
+        expect(
+            (
+                await post('/auth/request-app-root-dir', app.token, {
+                    app_uid: app.app_uid,
+                })
+            ).status,
+        ).toBe(200);
+        const root = `/${username}/AppData/${app.app_uid}`;
+        const files: string[] = [];
+        for (let i = 0; i < count; i++) {
+            const path = `${root}/notes-${i}.txt`;
+            const written = await post('/fs/write', app.token, {
+                fileMetadata: { path, size: 1, contentType: 'text/plain' },
+                fileContent: 'x',
+            });
+            expect(written.status).toBe(200);
+            files.push(path);
+        }
+        const lookalike = `${root}-keep`;
+        expect(
+            (await post('/fs/mkdir', token, { path: lookalike })).status,
+        ).toBe(200);
+        return { app, origin, root, files, lookalike };
+    };
+
+    const uninstall = (appUid: string, deleteData: boolean) =>
+        post('/auth/revoke-user-app', env.users.user.token, {
+            app_uid: appUid,
+            permission: '*',
+            deleteData,
+        });
+
+    it("deletes exactly the app's AppData folder", async () => {
+        const { app, root, files, lookalike } = await installWithFiles(3);
+
+        expect((await uninstall(app.app_uid, true)).status).toBe(200);
+
+        await vi.waitFor(async () => expect(await exists(root)).toBe(false));
+        for (const file of files) expect(await exists(file)).toBe(false);
+        expect(await exists(lookalike)).toBe(true);
+    });
+
+    /** A site rooted at `dir`, serving an index.html written by the app. */
+    const hostSite = async (appToken: string, dir: string) => {
+        const written = await post('/fs/write', appToken, {
+            fileMetadata: {
+                path: `${dir}/index.html`,
+                size: 6,
+                contentType: 'text/html',
+            },
+            fileContent: 'hosted',
+        });
+        expect(written.status).toBe(200);
+        const entry = (await env.server.stores.fsEntry.getEntryByPath(dir, {
+            skipCache: true,
+        }))!;
+        const subdomain = `uninstall-${Math.random().toString(36).slice(2, 10)}`;
+        await env.server.stores.subdomain.create({
+            userId: entry.userId,
+            subdomain,
+            rootDirId: entry.id,
+        });
+        const port = new URL(env.origin).port;
+        const serve = () =>
+            fetch(
+                `http://${subdomain}.site.puter.localhost:${port}/index.html`,
+            );
+        const served = await serve();
+        expect(served.status).toBe(200);
+        expect(await served.text()).toBe('hosted');
+        return serve;
+    };
+
+    it.each([
+        ['a folder inside it', '/www/public'],
+        ['the folder itself', ''],
+    ])('keeps AppData that hosts a site at %s', async (_case, sub) => {
+        const { app, root, files } = await installWithFiles(2);
+        const siteDir = `${root}${sub}`;
+        if (sub) {
+            const made = await post('/fs/mkdir', app.token, {
+                path: siteDir,
+                create_missing_parents: true,
+            });
+            expect(made.status).toBe(200);
+        }
+        const serve = await hostSite(app.token, siteDir);
+        const warn = vi.spyOn(console, 'warn');
+
+        expect((await uninstall(app.app_uid, true)).status).toBe(200);
+
+        await vi.waitFor(() =>
+            expect(warn).toHaveBeenCalledWith(
+                expect.stringContaining(`kept uninstalled app data at ${root}`),
+            ),
+        );
+        const served = await serve();
+        expect(served.status).toBe(200);
+        expect(await served.text()).toBe('hosted');
+        for (const file of files) expect(await exists(file)).toBe(true);
+    });
+
+    it('keeps the folder without deleteData', async () => {
+        const { app, root, files } = await installWithFiles(1);
+        const checks = vi.spyOn(
+            env.server.stores.fsEntry,
+            'deleteEntries',
+        );
+
+        expect((await uninstall(app.app_uid, false)).status).toBe(200);
+
+        expect(checks).not.toHaveBeenCalled();
+        expect(await exists(root)).toBe(true);
+        expect(await exists(files[0]!)).toBe(true);
+    });
+
+    it('stops once the user authorizes the app again', async () => {
+        FSService.SUBTREE_PAGE_SIZE = 1;
+        const { app, origin, root, files } = await installWithFiles(4);
+        const { fsEntry, permission } = env.server.stores;
+
+        // The app is opened again right after its first file is deleted.
+        const deleteEntries = fsEntry.deleteEntries.bind(fsEntry);
+        let reopened = false;
+        vi.spyOn(fsEntry, 'deleteEntries').mockImplementation(
+            async (entries) => {
+                await deleteEntries(entries);
+                if (!reopened) {
+                    reopened = true;
+                    await launch(origin);
+                }
+            },
+        );
+        const listGrants =
+            permission.listUserAppPermsFromPrimary.bind(permission);
+        let sawGrant = false;
+        vi.spyOn(permission, 'listUserAppPermsFromPrimary').mockImplementation(
+            async (userId, appId) => {
+                const rows = await listGrants(userId, appId);
+                if (rows.length > 0) sawGrant = true;
+                return rows;
+            },
+        );
+
+        expect((await uninstall(app.app_uid, true)).status).toBe(200);
+
+        await vi.waitFor(() => expect(sawGrant).toBe(true));
+        const left = (await Promise.all(files.map(exists))).filter(Boolean);
+        expect(left).toHaveLength(files.length - 1);
+        expect(await exists(root)).toBe(true);
+    });
+});