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Attachment schema

An attachment object describes one uploaded file. POST /attachments/upload returns one, attachment_get looks one up, and messages list them in attachments.

{
  "id": "550e8400-e29b-41d4-a716-446655440000",
  "name": "diagram.png",
  "mime_type": "image/png",
  "size": 28431,
  "url": "https://chat.example.com/attachments/550e8400-e29b-41d4-a716-446655440000",
  "expires_at": 1788782400,
  "permanent": false,
  "width": 1280,
  "height": 720
}
interface Attachment {
  id: string;
  name: string;
  mime_type: string;
  size: number;
  url: string;
  expires_at: number | null;
  permanent: boolean;
  width?: number;
  height?: number;
}
Field Description
id The upload’s ID. Send { "id": "..." } to attach it to a message.
name The file name given at upload.
mime_type The file’s MIME type, lowercased and without parameters.
size Size in bytes, after any image processing.
url Where to download the file. Usually GET /attachments/{id} on this server, but it can point to the server’s external storage instead.
expires_at When the upload expires, in Unix seconds. null when the server keeps uploads forever.
permanent Always false on the current server.
width, height Pixel size. Present only for PNG and JPEG images.

In messages

Section titled “In messages”

When a message references an upload by id, the server swaps in the stored record above. The sender may override width and height with numbers.

An attachment with an ID the server doesn’t recognise is stored exactly as the sender wrote it. So an attachment object on a message doesn’t prove the server hosts that file, and its fields may not match this schema.

Once an upload expires, the server stops serving it, but messages keep their copy of the object. Its url on this server then returns 404.

See also

Section titled “See also”