---
title: "Change one field"
description: "Set one existing field of a singleton, addressed like a data-atelier201-field attribute."
canonical: "https://atelier201.com/docs/api/content/set-field"
updated: "2026-11-06"
---

# Change one field

Requires `sites:write`. Changes the draft only. Visitors see nothing until you [publish](/docs/api/publishing/publish).

The `address` is `<singleton>:<JSON pointer>`, the same value as the page's `data-atelier201-field` attribute: `business:/tagline`, `business:/hours/2/close`, `navigation:/cta/label`. The document is validated after the change. See [Content model and media](/docs/platform/content-model).

```http
POST https://api.atelier201.com/v1/sites/{site_id}/fields
```

## Authorizations

- `Authorization` (bearer, in header, required)

## Path parameters

- `site_id` (`string`, required): The site's id, or its slug (the address before .atelier201.page).

## Body

`application/json`, required

- `address` (`string`, required, length: `3–200 chars`): <singleton>:<JSON pointer>, as the page's data-atelier201-field attribute says, e.g. business:/hours/2/close.
- `value` (`string | number | boolean`, required)
- `expected_hash` (`string,null`)

## Response

**200**: Change one field

- `data` (`Record<string, object>`, required)
- `data.singleton` (`string`, required)
- `data.revision` (`string`, required, length: `40–40 chars`): A Git commit id (40 hex characters) of the site's repository.
- `data.changed` (`boolean`, required)
- `request_id` (`string`, required)

```json
{
  "data": {
    "singleton": "<string>",
    "revision": "<string>",
    "changed": true
  },
  "request_id": "<string>"
}
```

**400**: Possible codes: invalid_request, unknown_field, invalid_parameter, invalid_cursor

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**401**: Possible codes: authentication_required, invalid_api_key, api_key_expired, api_key_revoked

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**402**: Possible codes: insufficient_credits

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**403**: Possible codes: insufficient_scope, feature_not_available, admin_required

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**404**: Possible codes: resource_not_found

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**409**: Possible codes: conflict, result_not_ready, idempotency_key_reused

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**410**: Possible codes: result_expired

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**413**: Possible codes: request_too_large

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**422**: Possible codes: request_too_large_for_plan

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**429**: Possible codes: rate_limited

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**500**: Possible codes: internal_error

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**503**: Possible codes: service_unavailable

- `error` (`object`, required)
- `error.type` (`string`, required)
- `error.code` (`string`, required)
- `error.message` (`string`, required)
- `error.param` (`string`)
- `error.docs_url` (`string`, required)
- `error.action_url` (`string<uri>`)
- `error.details` (`Record<string, object>`)
- `request_id` (`string`, required)

```json
{
  "error": {
    "type": "<string>",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "docs_url": "<string>",
    "action_url": "<string>",
    "details": {}
  },
  "request_id": "<string>"
}
```

**Example request**

```bash
curl --request POST \
  --url 'https://api.atelier201.com/v1/sites/<site_id>/fields' \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
  "address": "<string>",
  "value": "<string>"
}'
```