# Upload an attachment

> Upload an image to show in an issue's or a pull request's description or in a comment: a screenshot of a preview, say, instead of committing it to the repository. data is the file base64-encoded, name its file name (the image's alt text), content_type optional (checked against the bytes).

<div class="g1t-endpoint"><span class="g1t-method" data-method="post">POST</span><code>/repos/{owner}/{name}/attachments</code></div>

PNG, JPEG, GIF and WebP of at most 10 MB; a larger file is refused with 413 too_large, another type (SVG, PDF, anything its bytes do not show to be one of those) with 415 unsupported_type. Anyone who may comment on the repository may. Returns its id, url (on the usercontent origin, g1tusercontent.com on g1t.sh), name, size, content_type, and markdown (`![name](url)`) to paste into the body or summary of [`create_issue`](/reference/api/issues/create-issue/), [`update_issue`](/reference/api/issues/update-issue/), [`add_comment`](/reference/api/issues/add-comment/), [`create_pull_request`](/reference/api/pull-requests/create-pull-request/) or [`mark_pull_request_ready`](/reference/api/pull-requests/mark-pull-request-ready/). Its address is its permission: anyone given it can see the image, even one from a private repository. Over MCP the file travels in the tool call, so keep it small (a few hundred KB); `g1t attach FILE` uploads one from disk and prints the markdown.

`data` is the file base64-encoded: `base64 -w0 preview.png`. Paste `markdown` into the `body` of an issue, pull request or comment, or a pull request's `summary`. The type is read from the bytes; a file over 10 MB is refused with `413` (`too_large`), one that is not a PNG, JPEG, GIF or WebP with `415` (`unsupported_type`). From a shell, `g1t attach preview.png` does all of it and prints the markdown.

- **Authentication:** Required. Send an [access token](/reference/api/#authentication) as `Authorization: Bearer`.
- **MCP tool:** [`issue`](/reference/mcp/#issue) with `action` `attach`, and the same inputs
- **Scope:** An access token needs [`issues:write`](/guides/authentication/#scopes).

## Path parameters

| Name | Type | Required | Description |
| --- | --- | --- | --- |
| `owner` | string | Yes | The workspace that owns the repository. |
| `name` | string | Yes | The repository's name. |

## Body parameters

Send a JSON object. Names are `snake_case`, as in responses; the `camelCase` spelling is accepted too.

| Name | Type | Required | Description |
| --- | --- | --- | --- |
| `name` | string | Yes | The file's name, such as preview.png: the image's alt text in the markdown. |
| `content_type` | string | No | What the file is. Optional: it is read from the bytes, and refused when it says otherwise. One of `image/png`, `image/jpeg`, `image/gif`, `image/webp`. |
| `data` | string | Yes | The file, base64-encoded: PNG, JPEG, GIF or WebP of at most 10 MB. |

## Example request

```sh
curl -X POST https://api.g1t.sh/repos/flagon-io/session-lab/attachments \
  -H "Authorization: Bearer $G1T_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "preview.png",
    "content_type": "image/png",
    "data": "iVBORw0KGgoAAAANSUhEUgAA…"
  }'
```

## Example response

A successful request answers `200` with:

```json
{
  "id": "3f9c2a7e5b1d48c6a0e7f4b2d9c81a6e5f3b7d2c9a4e8f1b6c0d5a7e2f9b3c41",
  "name": "preview.png",
  "url": "https://g1tusercontent.com/attachments/3f9c2a7e5b1d48c6a0e7f4b2d9c81a6e5f3b7d2c9a4e8f1b6c0d5a7e2f9b3c41",
  "markdown": "![preview.png](https://g1tusercontent.com/attachments/3f9c2a7e5b1d48c6a0e7f4b2d9c81a6e5f3b7d2c9a4e8f1b6c0d5a7e2f9b3c41)",
  "content_type": "image/png",
  "size": 184213
}
```

## Errors

A failed request answers with one of these statuses and a body like `{"error": {"code": "not_found", "message": "Repository not found."}}`. See [errors](/reference/api/#errors).

| Status | Code | When |
| --- | --- | --- |
| 401 | `unauthenticated` | A token is required, or the one sent is not valid. |
| 403 | `forbidden` | The token is valid but not allowed to do this, such as a member-only change, or a token without the scope it needs. |
| 404 | `not_found` | It does not exist, or you cannot see it. |
| 409 | `conflict` | The request conflicts with the current state. |
| 422 | `invalid` | The input is not valid. `message` says which field and why. |