# Upload an attachment

> POST /attachments

Source: https://docs.trykintsugi.com/reference/2026-07-21/upload-an-attachment

POST /attachments

Upload an attachment

Attach a document to a related entity in the resolved organization, as `multipart/form-data` with the file in the `file` part and `relatedEntityId` and `relatedEntityType` as form fields. Returns the stored attachment's metadata. Returns 404 if the related entity does not exist or belongs to an organization your credential cannot access. The file must be at most 10 MB.

Category: Attachments

Response fields:
id (string, required) - Kintsugi's unique identifier for the attachment.
fileName (string, required) - Name the file was uploaded under.
contentType (string, required) - Media type of the file.
size (integer, required) - Size of the file in bytes.
relatedEntity (RelatedEntityRef, required) - The entity this attachment is held against.
  id (string, required) - Kintsugi's unique identifier for the related entity.
  type (string, required) - Kind of entity the attachment is held against.
uploadedAt (string, required) - When the attachment was uploaded, as an RFC-3339 UTC timestamp.

Response statuses: 201, 400, 401, 403, 404, 409, 413, 422

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