Debug a running Node process with breakpoints and the inspector

console.log is scattered through six files and you still can't tell which branch the code actually takes.

IntermediateRead 6 minDoing: about 30 minutes8 steps

What you'll have at the end

The exact line causing a wrong branch found live with a breakpoint and a watched value, fixed, and confirmed by resending the same request that used to come back wrong.

Before you start

You need

A Node process you started yourself, still running, that you can reach from a terminal on the same machine or one you can shell into.

Not covered

Finding a memory leak or a slow endpoint, which needs a heap snapshot or a CPU profile instead of a paused breakpoint.

Leans on

Node.js Cheat SheetCovers the inspector agent this recipe turns on, and the flag that starts a process with it already running.
Chrome DevTools Cheat SheetCovers every debugger control this recipe uses: a line breakpoint, stepping one line at a time, and a watch expression that updates as you go.

8 steps

Where to go next

Two heap snapshots and the leak they were hiding

when the process is slow or its memory keeps climbing instead of one specific wrong branch

Checked 25 Aug 2026

Part of the Node.js cookbook