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How to fix JavaScript console errors

Best practices1 min readFixes check console-errors

Errors in the console mean something on the page did not work. They are the fastest way to find broken features.

Step by step, with screenshots: Console errors and deprecated APIs: what the report flags →

Check your own site

Runs this check and the other 186, free, in about 45 seconds.

What a passing site looks like

  • No JavaScript errors while loading the pagewarning · −1.5 ptseffort M

JavaScript errors on load

Why it matters. Each error means a script stopped part-way, so a slider, form or tracker may silently not work for some visitors. Errors also cost time on the main thread.

How to fix it.
  1. Open the technical detail, then the browser console (F12) on the page, and fix the errors from the top; the first one often causes the rest.
  2. Check for plugins or scripts that were removed but are still referenced.

Filed under Best practices. Copy is generated from the same catalogue that scores every report, so what you read here is what the report says.