Error Tracking

VitalSentinel automatically captures JavaScript errors and resource loading failures experienced by your website visitors, helping you identify and fix issues before they impact user experience.

This page is part of RUM Monitoring and lives at Domain → RUM → Errors.

How It Works

The RUM script automatically captures three kinds of errors:

1. JavaScript Errors - Uncaught exceptions (window.onerror)
2. Unhandled Promise Rejections - Rejected promises with no handler
3. Resource Errors - Failed image, script, stylesheet, video, audio, and iframe loads

The error list shows individual error events by default. You can switch to a grouped view that aggregates errors by type (the message up to the first colon), with an occurrence count and affected-session count per group.

Dashboard Overview

Summary Cards

At the top of the page:

Error List

The list has two views, toggled at the top right:

• Events (default) – individual error events, 50 per page. Each row shows the error message, its type, the source file and line, the environment (browser and OS), and when it occurred. Expand a row for full detail.
• Types – errors grouped by kind (the message up to the first colon). Each group shows its type, when it was last seen, the number of occurrences, and the number of affected sessions. Expand a group to see its latest example events.

Search and Filters

Above the list you'll find:

• Search - free-text match against the error message, type, and URL.
• Type filter - JavaScript, Resource, or Unhandled Rejection (the options reflect the error types present in your data).
• Browser, OS, and device filters - narrow to a specific environment.
• Expand a row - see the captured stack trace, resource details, environment, and page context.

Filtering Errors

Filter the error list by:

Error Type

• JavaScript - Runtime JavaScript exceptions
• Resource - Failed resource loads (images, scripts, stylesheets, and similar)
• Unhandled Rejection - Promise rejections with no handler

Browser

Filter by browser to identify browser-specific issues:

• Chrome
• Firefox
• Safari
• Edge

Operating System

Filter by OS to find platform-specific problems:

• Windows
• macOS
• iOS
• Android
• Linux

Device Type

Filter by device category:

• Desktop
• Mobile
• Tablet

Error Details

Expand any error event to see its full context:

Error Details

Type, message, source file and line, and – for resource errors – the failing resource URL and element.

Environment

Browser and version, operating system, device type, and country.

Context

Page URL, referrer, and session ID.

Stack Trace

The captured stack trace, when available.

Common Error Types

Uncaught TypeError

Usually caused by:

• Accessing properties of undefined/null
• Calling non-functions
• Invalid type operations

Example:

Uncaught TypeError: Cannot read property 'foo' of undefined

Uncaught ReferenceError

Usually caused by:

• Using undefined variables
• Typos in variable names
• Script loading order issues

Example:

Uncaught ReferenceError: myFunction is not defined

Resource Loading Errors

Failed to load external resources:

Best Practices

Prioritize by Impact

Focus on errors affecting the most sessions:

1. Sort by affected sessions percentage
2. Fix high-impact errors first
3. Monitor trends after fixes

Check Browser Distribution

If an error only occurs in one browser:

• Check browser compatibility
• Review polyfills
• Test in that browser specifically

Monitor After Deployments

After releasing new code:

1. Check for new errors
2. Compare error counts before/after
3. Roll back if necessary

Set Up Alerts

Create alerts for error spikes:

1. Go to Alerts
2. Create a RUM alert
3. Set the metric to Error Rate within last 24h and enter a threshold percentage (for example, 5%)
4. Get notified when errors increase

Related Features