LINE error 410: The content is gone

The status codes table defines 410 Gone as "access to the resource that is no longer available," and on the content endpoints the documented example is precise: "if the user unsends a message (410 Gone)" the body is {"message":"The content is gone"}. The message ID was real and the content existed - but the user withdrew it, and LINE honors the unsend by cutting off API access to the bytes.

The semantic difference from 404 not found is worth encoding in your handler: 404 means the ID never referred to retrievable content in this channel (or it aged out), while 410 means it did exist and was deliberately removed. When a user unsends a message, your bot also receives an unsend webhook event carrying the messageId - the reference pairs these mechanisms, and well-behaved bots are expected to delete their stored copy in response, not just note the failure.

410 is terminal by design. There is no endpoint, header, or support path that restores unsent content, and retrying is pointless. If your product depends on captured media (receipts, verification photos), the only robust design is downloading content immediately on the message webhook - after an unsend, the API-side copy is gone regardless of retry strategy.

// If the user unsends a message (410 Gone)
{
  "message": "The content is gone"
}

Download user media at webhook time and store it under your own retention policy, then treat LINE's copy as already deleted. Process unsend events as deletion commands against your store - that keeps you consistent with user intent and makes 410 a non-event operationally. Distinguish 404, 410, and success in metrics so a spike in unsends is visible; see media limits for the retrieval endpoints involved.