> ## Documentation Index
> Fetch the complete documentation index at: https://docs.base44.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Save an app file
> This API is in beta. Endpoints, fields, and behavior may still change, so avoid depending on it in production.
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](/api-reference/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](/api-reference/get-app) returns.
This endpoint accepts a personal API key. Workspace API keys are not authorized for it and are rejected with a 403.
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.
## OpenAPI
````yaml /developers/references/app-management/app-management-openapi.json post /api/apps/{app_id}/coding/write
openapi: 3.1.0
info:
title: Base44 App Management API
version: 1.0.0
servers:
- url: https://app.base44.com
security:
- ApiKeyAuth: []
paths:
/api/apps/{app_id}/coding/write:
post:
summary: Save an app file
description: >-
This API is in beta. Endpoints, fields, and behavior may still
change, so avoid depending on it in production.
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](/api-reference/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](/api-reference/get-app) returns.
This endpoint accepts a personal API key. Workspace API keys are
not authorized for it and are rejected with a 403.
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.
operationId: write_file_api_api_apps__app_id__coding_write_post
parameters:
- name: app_id
in: path
required: true
schema:
type: string
description: ID of the app whose code to change.
title: App Id
description: ID of the app whose code to change.
example: 6820f3a4e7b91d003c45a1f2
requestBody:
required: true
content:
application/json:
schema:
title: SaveAppFile
type: object
required:
- file_path
- content
properties:
file_path:
type: string
description: Path of the file, relative to the app root.
content:
type: string
description: >-
Full contents to save. An empty string deletes the file,
which is this endpoint's convention rather than a way to
blank one.
example:
file_path: src/pages/About.jsx
content: |
export default function About() {
return About
;
}
responses:
'200':
description: The app after the write.
content:
application/json:
schema:
$ref: '#/components/schemas/AppSummary'
'401':
description: Missing or invalid credentials.
'403':
description: >-
You don't have access to this app, or you used a workspace API key.
Writing a backend function also needs a Builder plan or higher on
the app's workspace.
'404':
description: App not found.
'409':
description: >-
The app is on a branch this change can't be made on: a branch that
has been merged or closed, a protected main, or a path the branch
refuses.
'422':
description: >-
A backend function in this write failed to build. The detail carries
the compiler diagnostics.
components:
schemas:
AppSummary:
properties:
id:
anyOf:
- type: string
- type: 'null'
title: Id
description: ID of the app.
example: 6820f3a4e7b91d003c45a1f2
name:
anyOf:
- type: string
- type: 'null'
title: Name
description: Display name of the app.
example: My CRM
slug:
anyOf:
- type: string
- type: 'null'
title: Slug
description: >-
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.
example: my-crm-3c45a1f2
user_description:
anyOf:
- type: string
- type: 'null'
title: User Description
description: >-
Description of the app, or `null` if none was set. On a newly
created app this holds the original prompt text.
example: A CRM to track leads and deals
created_by:
anyOf:
- type: string
- type: 'null'
title: Created By
description: Email of the user who created the app.
example: developer@example.com
created_date:
anyOf:
- type: string
format: date-time
- type: 'null'
title: Created Date
description: Time the app was created, as a UTC timestamp in ISO 8601 format.
example: '2026-08-01T09:15:00'
updated_date:
anyOf:
- type: string
format: date-time
- type: 'null'
title: Updated Date
description: >-
Time the app document was last written, as a UTC timestamp in ISO
8601 format.
example: '2026-08-02T14:30:00'
status:
anyOf:
- $ref: '#/components/schemas/AppStatusResponse'
- type: 'null'
description: >-
The app's current build status. Poll while a build is in progress to
watch it finish. This tracks building, not publishing.
last_deployed_at:
anyOf:
- type: string
format: date-time
- type: 'null'
title: Last Deployed At
description: >-
Time the app was last published, as a UTC timestamp in ISO 8601
format, or `null` if it has never been published.
example: '2026-08-02T14:30:00'
screenshot_url:
anyOf:
- type: string
- type: 'null'
title: Screenshot Url
description: >-
URL of a screenshot of the published app. Captured shortly after
each publish, so it can briefly lag or be `null` right after
publishing.
example: https://storage.base44.com/screenshots/6820f3a4e7b91d003c45a1f2.png
preview_screenshot_url:
anyOf:
- type: string
- type: 'null'
title: Preview Screenshot Url
description: >-
URL of a preview screenshot taken before publishing, distinct from
`screenshot_url`, or `null` if none has been captured.
example: https://storage.base44.com/previews/6820f3a4e7b91d003c45a1f2.png
type: object
title: AppSummary
description: An app in a workspace, limited to the properties the caller requested.
AppStatusResponse:
properties:
state:
type: string
enum:
- ready
- processing
- error
title: State
description: >-
Where the app is in its build lifecycle. Ready means idle with no
build in progress, processing means the app is being generated or
modified, and error means the last build failed. This tracks
building, not publishing.
example: ready
details:
anyOf:
- type: string
- type: 'null'
title: Details
description: >-
Human readable note about the current state, such as what is being
processed or why it failed, or `null` when there is nothing to
report.
example: Publishing app
request_id:
anyOf:
- type: string
- type: 'null'
title: Request Id
description: >-
ID of the request that last changed the status, or `null` if the
status has never changed. Useful when reporting an issue.
example: a1b2c3d4e5f67890abcdef12
last_updated_date:
anyOf:
- type: string
format: date-time
- type: 'null'
title: Last Updated Date
description: >-
Time the status was last updated, as a UTC timestamp in ISO 8601
format.
example: '2026-08-02T14:30:00Z'
error_source:
anyOf:
- type: string
- type: 'null'
title: Error Source
description: >-
Where the failure originated when `state` is `error`, or `null`
otherwise. A value of `paywall` means the work was blocked because
the app's workspace has no credits left.
example: build
paywall_context:
anyOf:
- $ref: '#/components/schemas/PaywallStatusContextResponse'
- type: 'null'
description: >-
Present when the operation was blocked by a plan limit, describing
what was evaluated, or `null` otherwise.
type: object
required:
- state
title: AppStatusResponse
description: The app's current build status.
PaywallStatusContextResponse:
properties:
billing_organization_id:
type: string
title: Billing Organization Id
description: ID of the billing organization the paywall was evaluated against.
example: 67e0b12c4d8a3f005b21c9e4
user_id:
type: string
title: User Id
description: ID of the user the paywall was evaluated for.
example: 6706af53b9c1e2004a37d85f
evaluated_at:
type: string
format: date-time
title: Evaluated At
description: >-
Time the paywall condition was evaluated, as a UTC timestamp in ISO
8601 format.
example: '2026-08-02T14:30:00Z'
type: object
required:
- billing_organization_id
- user_id
- evaluated_at
title: PaywallStatusContextResponse
securitySchemes:
ApiKeyAuth:
type: apiKey
in: header
name: api_key
description: Personal API key.
````