Save an app file

Changed on

<Info>This API is in beta. Endpoints, fields, and behavior may still change, so avoid depending on it in production.</Info>

Saves a file into the app, the same way saving in the app editor does.

Base44 writes the file, applies it to the app, and takes care of what the path implies: a backend function is redeployed, an entity or agent schema is parsed and validated, and a change that affects row-level security records a revertible notice on the app's chat.

Sending an empty content deletes the file. That is the app editor's own convention for this path, so treat an empty string as a delete rather than as a way to blank a file.

Paths are relative to the app root. Entity and agent schemas, workflows and email templates each have one canonical location, and a legacy shorthand is refused with a 400 naming the canonical form. A path that escapes the app is refused the same way.

Writing a backend function deploys it, so the request takes as long as the deploy and answers 422 carrying the compiler's diagnostics when the code doesn't build. Backend functions also need a Builder plan or higher on the app's workspace. Use Save several app files to write a batch of frontend files in one call.

Set branch_id to save the file on a branch instead of main. The change goes to the branch's own code, and a backend function is deployed for the branch only. On a branch, files that define the app's resources, such as entity and agent schemas, are refused with a 409, except on an app imported from GitHub. To add entities or fields on the branch, use Send chat message with the same branch_id. Other resource changes must be made on main.

The response is the app document as it stands after the change, the same shape Get app returns. On a branch, it's main's app document, so it doesn't show the change.

<Note>This endpoint accepts a personal API key. Workspace API keys are not authorized for it and are rejected with a 403.</Note>

<Warning>The response includes fields beyond the ones documented here. Don't rely on undocumented response fields, as they can change at any time. Send only the fields documented here. Other request fields are not supported and their behavior can change.</Warning>

post/api/apps/{app_id}/coding/write

Request

  • Base URL: https://app.base44.com
  • URL: https://app.base44.com/api/apps/{app_id}/coding/write
  • Auth: HTTP bearer

Path parameters

app_idstring required

ID of the app whose code to change.

Query parameters

branch_idstring

ID of the branch to work on, as returned by List branches. Omit it to work on the app's main branch.

Request body

file_pathstring required

Path of the file, relative to the app root.

contentstring required

Full contents to save. An empty string deletes the file, which is this endpoint's convention rather than a way to blank one.

Example request

{
  "content": "export default function About() {\n  return <h1>About</h1>;\n}\n",
  "file_path": "src/pages/About.jsx"
}

Response

The app after the write. With branch_id, main's app, which a branch write doesn't change.

idstring

ID of the app.

created_datestring date-time

Time the app was created, as a UTC timestamp in ISO 8601 format.

updated_datestring date-time

Time the app document was last written, as a UTC timestamp in ISO 8601 format.

created_bystring nullable

Email of the user who created the app.

organization_idstring nullable

ID of the workspace the app belongs to.

app_typestring

Kind of app, set when it's created. One of user_app (a web app), user_agent (an AI agent), mobile_app (a native mobile app), user_game (a game), slide (a presentation), or imported_app (an app imported from an existing code repository). List apps returns it as stored, so an older agent app can report agent instead of user_agent, and some older apps don't include it. Get app always returns one of the values above.

namestring

Display name of the app.

user_descriptionstring nullable

Description of the app, or null if none was set. An app created without a name gets a generated description once a build turn changes it.

logo_urlstring nullable

URL of the app's logo, or null if it has none. Set it with Set app logo or Generate app logo.

social_image_urlstring nullable

URL of the image shown when the app is shared on social platforms, or null if none was set, in which case the logo is shown instead. Set it with Set social image.

public_settings'private_with_login' | 'public_with_login' | 'public_without_login' | 'workspace_with_login'

Who can open the published app. Each value is described under Update app, which also changes it.

hide_entity_created_byboolean

Whether the app's entity records leave out the email of the user who created each one (created_by). Newer apps always leave the email out, whatever this is set to.

is_remixableboolean

Whether others can remix the app. While it's true, the published app also shows the Base44 badge if public_settings is public_with_login or public_without_login.

main_branch_protectedboolean

Whether the app's main branch is protected, so changes to main must go through a branch that's merged back. Always true for imported apps. Change it with Set main branch protection.

slugstring nullable

URL slug for the app, auto generated from the name and app ID or set to a custom value, or null if the app has no slug yet. The published URL is built from it.

is_unpublishedboolean

Whether the app was taken offline with Unpublish app and hasn't been published again since. While it's true, the published URL is offline and last_deployed_at still shows the last publish.

last_deployed_atstring date-time nullable

Time the app was last published, as a UTC timestamp in ISO 8601 format, or null if it has never been published.

screenshot_urlstring nullable

URL of a screenshot of the published app. Captured shortly after each publish, so it can briefly lag or be null right after publishing.

preview_screenshot_urlstring nullable

URL of a preview screenshot taken before publishing, distinct from screenshot_url, or null if none has been captured.

owner_idstring nullable

ID of the user who owns the app. It starts as the creator and changes when ownership is transferred.

dev_environment_enabledboolean

Whether test data is on, which gives the app a test database next to its live one.

Example response

{
  "id": "6820f3a4e7b91d003c45a1f2",
  "created_date": "2026-08-01T09:15:00",
  "updated_date": "2026-08-02T14:30:00",
  "created_by": "developer@example.com",
  "organization_id": "67e0b12c4d8a3f005b21c9e4",
  "app_type": "user_app",
  "name": "My CRM",
  "user_description": "A CRM to track leads and deals",
  "logo_url": "https://storage.base44.com/6820f3a4e7b91d003c45a1f2/3f2504e0_logo.png",
  "social_image_url": "https://storage.base44.com/6820f3a4e7b91d003c45a1f2/7c9e6679_social.png",
  "public_settings": "public_with_login",
  "auth_config": {
    "enable_username_password": true,
    "enable_google_login": true
  },
  "hide_entity_created_by": true,
  "slug": "my-crm-3c45a1f2",
  "last_deployed_at": "2026-08-02T14:30:00",
  "screenshot_url": "https://storage.base44.com/screenshots/6820f3a4e7b91d003c45a1f2.png",
  "preview_screenshot_url": "https://storage.base44.com/previews/6820f3a4e7b91d003c45a1f2.png",
  "owner_id": "6706af53b9c1e2004a37d85f",
  "status": {
    "state": "ready",
    "details": "Publishing app",
    "request_id": "a1b2c3d4e5f67890abcdef12",
    "last_updated_date": "2026-08-02T14:30:00Z",
    "error_source": "build",
    "paywall_context": {
      "billing_organization_id": "67e0b12c4d8a3f005b21c9e4",
      "user_id": "6706af53b9c1e2004a37d85f",
      "evaluated_at": "2026-08-02T14:30:00Z"
    }
  }
}

Changes

  • c23775445de2Revision changes
    • breaking

      query request parameter branch_id list-of-types was narrowed by removing types null

    • info

      for the query request parameter branch_id, the type was generalized from no type to string

  • 4e0beb03385bRevision changes
    • info

      added the new optional query request parameter branch_id