How to detect frontend errors on a live website
Learn how live frontend error monitoring captures JavaScript errors, unhandled promises, broken resources, and failed browser requests with session context.
Frontend errors happen in the visitor browser
Frontend errors are failures that happen inside the user’s browser. They can include JavaScript exceptions, unhandled promise rejections, broken images or scripts, failed API calls, and custom application warnings.
These errors may not appear in backend logs, so teams need browser-side monitoring to see what visitors actually experienced.
What HeronSignal captures
HeronSignal can capture runtime errors, failed resources, optional console logs, custom logs, and network failures. Each log can be connected to the page, session, browser, country, device, and user journey around the failure.
- window.onerror runtime JavaScript errors
- Unhandled promise rejections
- Failed scripts, stylesheets, images, and other resources
- Failed or slow fetch and XMLHttpRequest calls
- Manual logs through window.heronsignal.log(...)
How to use the data
The best frontend error workflow is not only counting errors. It is opening the affected session, seeing what happened before the error, and checking whether it happened near an important funnel step such as signup, checkout, or demo request.
Ready to monitor real website experience?
Use HeronSignal to connect real visitor signals, frontend diagnostics, funnels, and AI guidance.