DataSag guides · Updated 27 October 2026

Load analytics without blocking rendering on SvelteKit

Use the platform's non-blocking external script mechanism and install the tracker once. Measure the published page before and after the change; script size alone cannot predict the effect on your website. This guide applies to SvelteKit.

Start with the SvelteKit installation

Add the script to head in src/app.html, preserving %sveltekit.head% and the existing body template. That document template loads the tracker once for the application. Replace the public key before building and deploying.

Putting the tracker in a route component can reinstall it on navigation. Keep browser calls out of server load functions and test both direct entry and client-side navigation.

Use the public project key from the DataSag project you are inspecting. A test on a preview domain does not confirm that the production domain has the same code or settings.

Load analytics without blocking rendering in SvelteKit

  1. Use the deferred external script in src/app.html and preserve the SvelteKit document placeholders. Avoid adding another loader in a layout onMount callback while the template already owns the installation.
  2. Measure a production build through the deployed adapter. A local development session can include reload behavior and assets that differ from the published app, so it is not the final timing comparison.
  3. Inspect a direct nested entry and a later client navigation separately. Check when the first intended browser action occurs relative to tracker availability, especially if you experiment with loading later than the document reference.

The production app template provides one non-blocking load with timing measured against the actions the app needs to observe.

Complete the collection checks

  1. Record a baseline of the published page using the same browser, device emulation and network settings you will use for comparison. Include a representative content page, not only the homepage.
  2. Use defer for a normal external HTML script, or the framework-specific loading strategy shown in the installation example. Do not add a parser-blocking synchronous script as a shortcut.
  3. Keep one installation in the shared document or layout. Duplicate execution adds work even if the browser reuses the downloaded file.
  4. Inspect the Network waterfall for tracker.js and /api/track. Compare transfer size, timing and request count on a cold load and a cached load.
  5. Check that measurement still starts at the intended point. Loading only after idle or interaction can omit short visits and early clicks; performance and coverage must be evaluated together.
  6. Repeat the measurements and record variability. Report measured results for your page rather than claiming a universal speed improvement or zero performance cost.
// Browser Console, after loading the published page:
performance.getEntriesByType('resource')
  .filter(entry => entry.name.includes('/tracker.js'))
  .map(entry => ({ url: entry.name, durationMs: entry.duration }));
// Cross-origin transfer details may be unavailable.

What a successful check looks like

The script uses a non-blocking loading mechanism, appears once and records the intended visits. Any performance claim comes from repeatable measurements of the actual site.

Record the public path you tested, the browser state, the approximate time and the observed request. Check one direct page load and one later navigation so the result covers more than the homepage.

Common mistake

A faster lab result does not prove every visitor has a faster experience. Avoid mixing a warm-cache result with a cold-load baseline.

Installation snippet for SvelteKit

The shared installation belongs in the head of src/app.html. Use this as the installation reference while checking the procedure above.

<script defer src="https://www.datasag.com/tracker.js" data-datasag-key="YOUR_PUBLIC_KEY"></script>

Related SvelteKit guides

Full SvelteKit setup guide · Search and AI visibility

References

Official SvelteKit documentation covers the integration point. For DataSag data handling, read the privacy policy. Use support if a request fails after these checks.