How Automatic Error Grouping Works

Understand how Lognitor groups individual errors into actionable error groups.

The Problem

A single bug can generate thousands of identical error logs. Showing each one individually makes it impossible to prioritize.

How Grouping Works

Lognitor automatically generates a fingerprint for each error based on:

1. Error type — e.g., TypeError, ConnectionError
2. Error message — normalized to remove dynamic values
3. Stack trace location — the file and line where the error originated

Errors with the same fingerprint are grouped together. If the same TypeError: Cannot read properties of undefined fires 500 times from payment.js:42, you see it as one error group with a count of 500.

What You See

Each error group shows:

• Error type and message
• Total event count and affected users
• First seen / last seen timestamps
• Trend direction (increasing, decreasing, or flat)
• The release that introduced it

Custom Fingerprints

If automatic grouping doesn't match your needs, you can set a custom fingerprint:

Lognitor.error('Payment failed', {
  error: new Error('Card declined'),
  fingerprint: 'payment-card-declined',
});

All errors with the same fingerprint value are grouped together regardless of their stack trace.