Make sense of
your logs.

Shared formats run first. Each transport checks its threshold, then applies its own formats. A format returning false drops the event. Finalizers like json and printf set Symbol(message); later changes to other fields do not automatically update that output.

This previews formatting and npm-level filtering, not file or network I/O. Custom code runs in a disposable worker with a time limit and blocked network requests. Browser inspection formatting can differ from Node.js; timestamps and ms values vary. Avoid mutations of nested objects across transports: Winston uses shallow copies.