When a Mastodon post from your instance fails to reach followers on another server, you see no error on your screen. The post publishes locally, but remote users never receive it. This is a federation failure, and it often hides in the background jobs processed by Sidekiq, Mastodon’s task queue system. This article explains how to locate and read Sidekiq logs to trace the exact failure point, identify the remote server that rejected the activity, and apply the correct fix.
Federation failures can happen for many reasons: a remote instance is down, TLS certificates expired, the payload violates server limits, or the remote server blocked your domain. Sidekiq logs record every attempted delivery along with the HTTP response code and error message. By examining these logs, you can determine whether the problem is temporary, permanent, or caused by a configuration mismatch. This guide covers the log location, filtering methods, and common error patterns so you can resolve federation issues without guessing.
You will learn where Sidekiq logs reside in a default Mastodon installation, how to filter for failed federation jobs, and how to interpret the error fields. The article also includes steps to re-deliver failed activities and to adjust server settings when a remote instance consistently rejects your content.