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Save an app file

<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 builder's code 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 builder'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.

The response is the app document as it stands after the change, the same shape Get app returns.

<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

Path parameters

app_idstring required

ID of the app whose code to change.

ID of the app whose code to change.

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.

Response

The app after the write.

idstring nullable

ID of the app.

namestring nullable

Display name of the app.

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.

user_descriptionstring nullable

Description of the app, or null if none was set. On a newly created app this holds the original prompt text.

created_bystring nullable

Email of the user who created the app.

created_datestring date-time nullable

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

updated_datestring date-time nullable

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

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.

Example response

{
  "id": "6820f3a4e7b91d003c45a1f2",
  "name": "My CRM",
  "slug": "my-crm-3c45a1f2",
  "user_description": "A CRM to track leads and deals",
  "created_by": "developer@example.com",
  "created_date": "2026-08-01T09:15:00",
  "updated_date": "2026-08-02T14:30:00",
  "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"
    }
  },
  "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"
}

Changes

Changed in 1 of the 15 revisions of this API.1