RUM Data | Error Rate Breakdown

This document will help explain the data points and graphs under the Errors tab of a RUM report. This is a companion document for RUM, and is best used once you have generated a RUM snippet and are actively collecting data. 

For setup instructions, click here

Error Rate Over Time

This graph visualizes errors color-coded by type and compared against the pageviews for the URL, group, or domain you are monitoring with RUM. 

4xx Errors

4xx errors measure AJAX errors that a page relies on, and records status code 4xx if that call fails with status code 4xx.

An increase in 4xx errors could mean either your site may have missing pages, is rejecting user requests, or that certain endpoints are functioning as intended. Authorization being a good example where 4xx errors might be “acceptable”. 

5xx Errors

5xx errors measure AJAX errors that a page relies on, and records status code 5xx if that call fails with status code 5xx.

5xx errors, generally speaking, are not a part of normal operation and should be considered an indication that something is wrong. Usually these errors are at the server level. It is recommended to keep 5xx errors as close to 0% as possible. Even a small increase in 5xx errors could signal a growing problem and may require action from your team. 

JavaScript Errors

JavaScript errors reflect errors that occur when the browser is processing AJAX network requests, or bugs in JavaScript code that may cause processing to stop. These are errors the browser usually logs in red within the JavaScript console.

Some examples of requests not logged include: XHR/Fetch.

JavaScript errors can sometimes occur during normal operation (particularly due to 3rd party libraries and snippets) and a certain percentage may be expected. However, JavaScript errors can also signal a problem accessing certain resources or bugs in your site's JavaScript.

Errors By Code

RUM checks collect specific data on error codes encountered, which can assist in diagnostics. Click or filter for a specific URL or group to examine errors by code. 


Each error code is listed alongside the number of times the error was encountered, and a percentage representing the error rate. The error percentage represents a ratio for the number of pages or number of AJAX calls that experienced errors. Errors can be sorted by type.

Please note: 4xx and 5xx errors cannot be tracked for the main load of a page. If an AJAX error occurs during the loading of the main HTML page, which can cause that page to load incorrectly, we log that error as both an AJAX error and an error on the main HTML page.

Called URLs

View the AJAX calls made at a given URL or URL Group that resulted in errors. 

Want to see our checks in action? Check out our youtube-logov4.svg YouTube Library for more!

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