Cookie Banner Performance: Core Web Vitals Benchmark

Date: May 30, 2026 Author: GetCookies Team Category: Technical Reading Time: 12 min

"Does this cookie banner slow down my site?"

It's the #1 question developers ask. And for good reason. Interaction to Next Paint (INP) and Largest Contentful Paint (LCP) are Google ranking factors. A heavy CMP can tank your SEO scores.

We benchmarked GetCookies against the industry giants (OneTrust, Cookiebot, Termly). Here is the data.

The Weight Class

• GetCookies: 1.2 KB (Loader) / 18 KB (Full UI).
• Cookiebot: 46 KB (Base).
• OneTrust: 140 KB+ (Base).

Benchmark Results (Lighthouse Mobile)

Why the Difference?

1. The "Stubb" Loader: GetCookies loads a tiny ~1.6 KB stub immediately. This stub queues commands (like GTM events) but does not render pixels. The heavy lifting happens off the main thread.
2. No Layout Shift (CLS): Competitors often inject a top bar that pushes content down, causing a Cumulative Layout Shift penalty. GetCookies uses a floating overlay or a bottom bar with position: fixed to ensure zero layout shift.
3. Modern JS: We ship ES2026 modules. Competitors often ship bloated ES5 bundles to support Internet Explorer 11 (which is dead).

Optimization Tips for Any CMP

1. DNS Prefetch: Add <link rel="dns-prefetch" href="https://js.getcookies.io"> to your head.
2. Async vs Defer: Always use async. defer might execute too late (after other scripts have already fired illegally).
3. Self-Hosting: For maximum speed, proxy the script through your own Cloudflare worker (GetCookies Enterprise supports this).

Conclusion

Compliance shouldn't cost you performance. If your current CMP is adding 100ms+ to your Total Blocking Time (TBT), it is hurting your SEO. Switch to a performance-first architecture.