How Heavy Is an Analytics Script? How to Measure the Impact on Site Speed

A heavy or render-blocking analytics script slows your website down, and that can affect bounce rate, SEO, and conversions. The earlier version of this article had a benchmark button and comparison figures for RevKlik, GA4, and Plausible. We removed them because you could not reproduce the comparison figures and we had not documented how they were measured. This article replaces them with things you can check yourself.

Why Do Analytics Scripts Affect Speed?

Google uses Core Web Vitals as a page-experience signal. Heavy third-party scripts most often affect two metrics:

Largest Contentful Paint (LCP): a render-blocking script delays the largest element on screen.
Interaction to Next Paint (INP): long-running JavaScript on the main thread slows the response to clicks and taps.

That makes three things worth checking on any analytics tool: the script size, whether it loads without blocking render, and how it sends data.

What We Know About the RevKlik Script

These two facts come from the tracker code in our repository:

Size: klikapa.js is about 4 KB after gzip compression (about 4.3 KB in the build we checked).
How it sends data: events go out through fetch() with the keepalive: true option, so the request still completes if the visitor navigates away and the page does not wait on the server response.

The script is installed with the defer attribute, so it does not hold up HTML parsing:

<script defer data-site-id="your-site-id" src="https://app.revklik.com/klikapa.js"></script>

We deliberately do not list the size or latency of the GA4 and Plausible scripts. Both change between versions, so a number we write today may be wrong next month. Measure them yourself using the steps below.

How to Measure It Yourself

1. Script size after gzip

Run this in a terminal, replacing the URL with the script you want to check:

curl -s https://app.revklik.com/klikapa.js | gzip -c | wc -c

The result is the byte count after gzip. The same command works for any other analytics script, so you compare sizes using the same method.

2. Impact on page load time

Open your site in Chrome, then:

Open DevTools, go to the Network tab, tick Disable cache, and pick a network throttling profile that matches your visitors.
Load the page with the analytics script, then load it again without it.
Compare LCP in the Performance tab or in Lighthouse. Repeat a few times and take the median, because a single run is easy to misread.

3. Whether the script blocks rendering

In the Network tab, look at the Priority column and the waterfall. A script loaded with async or defer does not hold up HTML parsing. A synchronous script in <head> does. Lighthouse also flags render-blocking resources.

4. Data-sending latency

The event request runs in the background, so visitors do not see its timing directly. You can still find it in the Network tab by filtering for the tracking endpoint name and comparing the Time column. Results depend on your location, ISP, and network conditions, so do not draw conclusions from a single try.

About Server-Side Latency

RevKlik runs on Cloudflare Workers with a D1 database. Our configuration uses smart placement: the Worker runs near the D1 primary in Asia-Pacific rather than at the location closest to the visitor, so database queries do not travel a long way. That means “processed on the server closest to the visitor” is not accurate for every request, and we do not claim a specific latency figure. The architecture details are in edge-native analytics and building a SaaS with Workers and D1.

Summary

Check the gzip size, the defer or async attribute, and the way data is sent for every analytics tool.
Measure the impact on your own site, using devices and networks that represent your visitors.
Trust numbers you can repeat, including ours. For RevKlik, the number we know for sure is a script size of about 4 KB (gzip).

The tracker’s privacy side (first-party visitor ID, retention, and consent) is covered in analytics without third-party cookies.