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Conversion

Why I need error tracking before launch

Analytics tells you a page was visited; it does not tell you the signup button threw on Safari and the visitor left. Client errors are invisible from your side unless something captures them — and a launch is when you have the most traffic and the least idea which browsers it arrives on.

What 13x checks

This is rule conversion.error-tracking in the public registry: Errors are reported somewhere. It runs on every audit, against the pages we actually fetched, and its result is derived from the response rather than estimated.

Surface
Conversion
Score weight
4 of the readiness score
Scope
Runs on every audited page
Applies
To every site

Registry version 2026-07-30. Every rule is published, and the audit is deterministic — the same page produces the same finding every time.

The fix

The same text the audit hands you when this check fails on your own site.

Add an error reporter so client-side failures are visible to you rather than only to the visitor who hit them.

Sentry, Bugsnag, Rollbar and Highlight all have free tiers that comfortably cover a launch. The generic install is one script in <head>:

html code
<script
  src="https://browser.sentry-cdn.com/8.0.0/bundle.tracing.min.js"
  crossorigin="anonymous"
></script>
<script>
  Sentry.init({
    dsn: "https://examplePublicKey@o0.ingest.sentry.io/0",
    tracesSampleRate: 0.1,
    // Without this, a release cannot be blamed for a spike in errors.
    release: "example.com@1.0.0",
  });
</script>

Two settings worth getting right on day one:

- `release` — otherwise every error is attributed to "unknown" and you cannot tell which deploy introduced it. - A sample rate below 1.0 for traces. Errors should be captured at 100%; performance traces at 100% will exhaust a free tier during a traffic spike.

If you have a consent banner, load the reporter under the same gate as your other non-essential scripts, or configure it to send no IP address and no cookies.

Framework-specific versions

Where the change differs enough to be worth writing out separately.

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