DataSag guides · Updated 27 October 2026

Load analytics without blocking rendering on Gatsby

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 Gatsby.

Start with the Gatsby installation

Use the Gatsby SSR onRenderBody API to add one deferred external script through setHeadComponents. Merge the addition into an existing hook rather than overwriting it, and keep the React import required by your file format. Build and publish the generated site; inspect its HTML because this hook concerns generated documents.

A browser onRouteUpdate hook, a plugin and gatsby-ssr can all add analytics behavior. Do not add a second pageview sender without testing the current tracker. gatsby develop is not a substitute for checking generated production documents.

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 Gatsby

  1. Keep the deferred external script in the onRenderBody head addition and preserve existing Gatsby head output. Check plugins and browser hooks for another loader before changing timing.
  2. Measure the generated production site with fixed device, network and cache conditions. Gatsby development assets and generated pages have different behavior, so record the production build used for the comparison.
  3. Compare first-load timing with Gatsby Link navigation separately. Inspect the earliest action and script availability, and verify that a cached route transition does not cause another tracker initialization through a browser hook.

The built Gatsby site loads one non-blocking tracker with initial document and client-navigation costs distinguished.

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 Gatsby

The shared installation belongs in an onRenderBody head component in the root gatsby-ssr.js file. Use this as the installation reference while checking the procedure above.

const React = require("react");

// Merge into your existing onRenderBody hook if one exists.
exports.onRenderBody = ({ setHeadComponents }) => {
  setHeadComponents([
    <script key="datasag" defer
      src="https://www.datasag.com/tracker.js"
      data-datasag-key="YOUR_PUBLIC_KEY" />
  ]);
};

Related Gatsby guides

Full Gatsby setup guide · Search and AI visibility

References

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