# Concepts (/en/docs/developers/file/concepts)



## Purpose [#purpose]

`purpose` records how you intend to use an uploaded file. Uploads accept three values:

| Purpose      | Use and limitation                                                                                                                                                        |
| ------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `user_data`  | General input files. Required when referencing an image in a conversation.                                                                                                |
| `assistants` | Files intended for assistant or knowledge-store workflows. Uploading does not attach a file to an agent or store. Conversation image references reject this purpose.      |
| `vision`     | Accepts only PNG, JPEG, GIF or WebP images (detected from content); other content returns 400 `FILE_TYPE_UNSUPPORTED`. Conversation image references reject this purpose. |

`batch`, `fine-tune` and `evals` are not accepted upload purposes. Anthropic uploads are stored as `user_data`.

## Reuse a file ID [#reuse-a-file-id]

`/file/v1/files`, `/openai/v1/files` and `/anthropic/v1/files` share file IDs for the same account. Metadata and deletion work across these APIs. Download uploaded files through the native or OpenAI API; Anthropic downloads only support session output files.

* **Conversations:** reference a `user_data` image using `type: "file"` and `file.file_id`. Do not place the ID in `image_url.url`. Text and PDF file IDs are not currently accepted as conversation image input. See the [runnable image example](/en/docs/developers/model/guides/files).
* **Media libraries:** import the ID as `file_id` to create an asset. See [media files](/en/docs/api/native/media/assets).
* **Knowledge stores:** add `file_id` to a store to extract and index its content. See [knowledge concepts](/en/docs/developers/knowledge/concepts).
* **Agents:** attach a file to a session resource using `type: "file"`, `file_id` and `mount_path`. Setting `purpose=assistants` alone does not attach it. See [session resources](/en/docs/api/native/agent).

Session output metadata can include `scope`, `relative_path` and `revision`. List a session's files with `scope_id`; Anthropic requires `anthropic-beta: managed-agents-2026-04-01` for this filter.

## Expiry [#expiry]

Without an expiry setting, an uploaded file persists until deleted. `expires_after` measures seconds from `created_at`; the returned `expires_at` is the expiry timestamp. Expired files cannot be read or reused. See the [supported ranges](/en/docs/developers/file/limits-and-errors).

## Download safety [#download-safety]

Downloaded content identified as HTML, SVG, XML or JavaScript is served as an attachment. Responses use `X-Content-Type-Options: nosniff`. Detection uses content rather than the filename: uploaded HTML or SVG may be identified and returned as plain text. Downloading does not execute that content.

## Range downloads [#range-downloads]

Content downloads accept one `Range` interval: `bytes=0-1023`, `bytes=1024-` (to the end) or `bytes=-1024` (the last 1024 bytes). A satisfiable range returns 206 with `Content-Range`; a range beyond the file size returns 416. Every download response carries `Accept-Ranges: bytes`, so downloads can resume and audio or video can seek.

[API reference →](/en/docs/api/native/file) · [Cookbook →](/en/docs/cookbook)