Sending Crash Reports to Your Backend

CrashSense runs entirely in the browser. To persist crash data, you need to send reports to your own backend.

Using the onCrash Callback

The simplest approach is the onCrash callback:

import { createCrashSense } from '@crashsense/core';

const cs = createCrashSense({
  appId: 'my-app',
  onCrash: async (report) => {
    await fetch('https://your-api.com/crashes', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(report),
    });
  },
});

What's in the Report

Each report includes the full crash event with:

• Classification — category, subcategory, confidence score, severity
• Error details — type, message, parsed stack frames
• System state — memory usage and trends, CPU/long task metrics, network status
• Device info — user agent, viewport, device memory, hardware concurrency
• Breadcrumbs — last N user interactions, navigation, network requests, console messages
• Contributing factors — weighted factors with human-readable evidence strings

PII (emails, IPs, auth tokens, credit card numbers) is auto-scrubbed before the report reaches your callback.

Using a Plugin

For more complex integrations, use the plugin system:

import type { CrashSensePlugin, CrashEvent, CrashSenseCore } from '@crashsense/core';

const backendReporter: CrashSensePlugin = {
  name: 'backend-reporter',

  setup(core: CrashSenseCore) {
    console.log('Reporter initialized for', core.config.appId);
  },

  teardown() {},

  onCrashEvent(event: CrashEvent) {
    fetch('/api/crashes', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({
        category: event.category,
        subcategory: event.subcategory,
        severity: event.severity,
        message: event.error.message,
        fingerprint: event.fingerprint,
      }),
    }).catch(() => {});

    return event;
  },
};

const cs = createCrashSense({ appId: 'my-app' });
cs.use(backendReporter);

Tips

Error Handling

Always handle network errors in your crash reporting callback. A crash reporter that itself throws errors defeats the purpose:

onCrash: async (report) => {
  try {
    await fetch('/api/crashes', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(report),
    });
  } catch (err) {
    // Log locally but never throw
    console.warn('Failed to report crash:', err);
  }
},

Batching

For high-traffic applications, consider batching crash reports instead of sending each one individually:

const crashBuffer: unknown[] = [];

const cs = createCrashSense({
  appId: 'my-app',
  onCrash: (report) => {
    crashBuffer.push(report);

    if (crashBuffer.length >= 10) {
      const batch = crashBuffer.splice(0, 10);
      fetch('/api/crashes/batch', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(batch),
      }).catch(() => {});
    }
  },
});

Sending on Page Unload

Use navigator.sendBeacon to reliably send data when the page is closing:

window.addEventListener('beforeunload', () => {
  if (crashBuffer.length > 0) {
    navigator.sendBeacon(
      '/api/crashes/batch',
      JSON.stringify(crashBuffer),
    );
  }
});