What Does This Error Message Mean?

Error messages look scary, but they usually point to a simple mistake. The key is to find the first real error, not the last line in the list.

How to read it fast

  1. Find the first error line in the output.
  2. Look for the file name and line number.
  3. Fix that line first, then recompile.

Common patterns

  • missing semicolon: usually the line before the one shown
  • not declared in this scope: typo or missing include
  • expected ... : brackets or quotes not closed
Bottom line

Start at the first error line and fix it. Most of the errors after that are just noise.

Related: Why do I get expected semicolon before...? · Why does my code compile but not work? · How do I use Serial Monitor correctly?