A list of function calls shown in an error message that tells you exactly where in your code the error occurred.
Stack Trace is the trail of Function calls that an error message shows you when something goes wrong in your JavaScript code. It tells you not just what broke, but where — which file, which line, and which functions were involved.
A typical stack trace looks like this:
TypeError: Cannot read property 'length' of undefined
at PostsPage (posts.jsx:15:8)
at renderWithHooks (react-dom.js:1000)
at mountComponent (react-dom.js:2500)
Reading it from top to bottom:
Cannot read property 'length' of undefinedPostsPage in posts.jsx at line 15The most important line is usually the second one — that's YOUR code. Lines referencing react-dom.js or node_modules are Framework internals and usually not the source of your bug.
When Debugging, copy the error message and the first few lines of the stack trace. This gives Claude Code everything it needs to identify and fix the issue. The stack trace is especially useful when errors happen inside loaders, actions, or components — it pinpoints the exact location in your Route file where things went wrong.
Stack traces appear in the browser console (F12 → Console) and in your Terminal if you're running a Server.
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