Slack API · error code

Slack error request_timeout: POST data missing or truncated

ConfigurationHTTP 200Slack-side errors

Last verified against Slack API reference - chat.postMessage errors

What Slack returns
The method was called via a POST request, but the POST data was either missing or truncated.

What error request_timeout means

Despite the name, this is usually not about Slack being slow — it is about your request arriving incomplete. The documented description: "The method was called via a POST request, but the POST data was either missing or truncated." Slack received your POST, waited for the body, and got nothing or only part of it before giving up.

The mechanics behind a truncated body are transport-level: a Content-Length header that promises more bytes than are sent (classic when the body is built after headers, or mutated by middleware), a connection dropped mid-upload on a flaky network, a proxy or gateway buffering/limiting request bodies, or a client timeout shorter than the time needed to stream a large payload. Hand-rolled HTTP is over-represented here; the official SDKs compute lengths and stream bodies correctly.

Debug at the wire: capture what actually left your process (or hit the proxy) and compare declared versus transmitted length. If bodies are large — big Block Kit payloads, long text — also reconsider whether the content belongs in a message at all versus a file upload.

What it looks like

{"ok": false, "error": "request_timeout"}

Why it happens

  • Content-Length disagrees with the transmitted body (middleware mutation, manual header setting).
  • The connection dropped or timed out mid-body on a slow or unstable network path.
  • A proxy, gateway, or serverless layer strips or limits the request body.
  • A client-side timeout aborts the request while the body is still streaming.

How to fix Slack error request_timeout

  1. 1Reproduce with curl using the same payload; if curl succeeds, the defect is in your HTTP client or a middlebox.
  2. 2Stop setting Content-Length manually; let the client library compute it after all body mutations.
  3. 3Raise client timeouts for large payloads or shrink the payload (files instead of giant messages).
  4. 4Inspect proxies/gateways in the path for body-size limits and streaming behavior.
  5. 5Prefer the official SDKs, which handle body serialization and length correctly.

How to stop it recurring

Send Slack traffic through a well-tested HTTP client (ideally the official SDK), keep payloads modest, and add a wire-level integration test for your largest realistic payload so transport truncation shows up in CI rather than in production logs.

Official reference: Slack API reference - chat.postMessage errors. See all Slack error codes or the Slack limits and quotas.

Related codes

Error request_timeout - quick answers

What does Slack error request_timeout mean?

Despite the name, this is usually not about Slack being slow — it is about your request arriving incomplete. The documented description: "The method was called via a POST request, but the POST data was either missing or truncated." Slack received your POST, waited for the body, and got nothing or only part of it before giving up.

How do I fix Slack error request_timeout?

1. Reproduce with curl using the same payload; if curl succeeds, the defect is in your HTTP client or a middlebox. 2. Stop setting Content-Length manually; let the client library compute it after all body mutations. 3. Raise client timeouts for large payloads or shrink the payload (files instead of giant messages). 4. Inspect proxies/gateways in the path for body-size limits and streaming behavior. 5. Prefer the official SDKs, which handle body serialization and length…

Stop debugging Slack by hand

Connect the channel through Conferbot: tokens, webhooks and retries are handled, failures show as readable status.