To check a website for JavaScript errors, load it in a real browser with the developer console open and note every red error, including ones that appear only after you interact with the page. This free scan does that automatically: it opens your page in Chromium on desktop and at phone width, records console errors and failed network requests while it clicks the main button and follows links, and lists each error with the file it came from. Errors that happen only for logged-out visitors, which you never see while signed in, show up here.
What it checks
Console errors on load
Every error the page throws while loading is captured with its message and source file, so you can tell your own code from a plugin or a third-party script.
Errors after interaction
Some scripts only fail when a visitor does something. The scan clicks the main call to action and follows navigation, and records errors that appear then.
Failed network requests
Scripts, styles, images and API calls that return 404 or 500, or never load at all, are listed. A missing script file is one of the most common reasons a menu or form stops working.
Desktop and phone separately
Some scripts behave differently at small widths, such as mobile menus or sliders. Running at both sizes catches errors that happen only on one.
How to read your results
- Read the errors in order. The first one is often the cause and the rest are knock-on effects of a script that stopped halfway.
- Look at the file name. A file from a plugin, app or embed points at that vendor; a file from your theme or build points at your own code.
- Failed requests to files that no longer exist usually come from a removed plugin or app that left its script tag behind.
What an automated check can't tell you
- The scan sees errors in the visitor’s browser, not on your server. Server-side errors show up only as failed requests or error pages.
- Errors that occur only after logging in, or deep inside a multi-step flow, need a paid report covering more pages or the manual test.
- Warnings and messages that do not break anything are not all reported; the focus is on errors that affect visitors.
Want to see a full report before you scan? Here's a real sample report.
Frequently asked questions
How do I open the browser console?
In Chrome or Edge, right-click the page, choose Inspect, then the Console tab, or press F12. In Safari, enable the Develop menu in Settings > Advanced, then choose Develop > Show JavaScript Console.
Do JavaScript errors affect SEO?
They can. If an error stops your content from rendering, search engines that render pages may see less than a visitor would. More often the cost is to visitors: menus, forms and buttons that silently stop working.
Why does one JavaScript error break my whole menu?
Browsers stop running a script at the first unhandled error. If your menu code lives in the same file, or runs after the failing script, it never gets the chance to attach to the menu button.
Can I check JavaScript errors on my phone?
It takes extra setup: connecting the phone to a computer for remote debugging. This scan runs at phone width in a desktop browser engine, which catches most mobile-only errors without that setup.
Rather have a QA engineer test it by hand?
An automated check covers what a visitor sees on load. For logged-in flows, checkout, or a launch that has to go right, I'll test the site by hand.
- Up to 10 key pages tested by hand, not a scan
- Every flow a customer uses: forms, sign-up, checkout, booking
- Real mobile and desktop browsers
- A written report in plain language, with screenshots
- A 15-minute call to walk you through it
- 10 years of professional QA experience
Tell me about your site and I'll reply personally, usually the same day.
No payment now. I'll confirm scope and price first.
Related fix guides
Other free tools: Free mobile-friendly test · Contact form tester · Broken button checker · Free website bug checker · AI website tester
Built by Waqas Ahmad, QA engineer with 10 years of professional testing experience. Last checked October 26, 2026.
Sources: Yoast: find JavaScript errors with the console · Chrome DevTools: Console overview