Cookiebot: impact on page speed
Category: Consent management
Cookiebot shows the consent banner and controls which scripts may run. It has to load early, which puts its cost directly on the critical path of every first visit.
On 2.6 % of the 4108 homepages measured, Cookiebot is among the five heaviest third parties. Where it is, it takes a median of 84 ms of main-thread time; on the heaviest quarter of those sites it takes 154 ms or more.
2.6 %
of homepages: among the five heaviest third parties
84 ms
median main-thread time
154 ms
main-thread time on the heaviest quarter (p75)
151 KB
median transfer size
Distribution across homepages
Percentiles across 105 homepages with Cookiebot.
| Percentile | Main-thread time | Transfer size |
|---|---|---|
| p25 |
68 ms
|
146 KB |
| Median |
84 ms
|
151 KB |
| p75 |
154 ms
|
161 KB |
| p90 |
240 ms
|
437 KB |
In context
By median main-thread time, Cookiebot ranks 36th of 65 third parties in the benchmark, lighter than Clarity and heavier than Hotjar.
On 8.6 % of the homepages where it appears, Cookiebot alone uses 250 milliseconds of main-thread time or more, the mark from which Lighthouse flags third-party code.
Homepages with Cookiebot weigh 3.5 MB at the median (JavaScript: 1.5 MB), homepages without it 4.3 MB (JavaScript: 1.6 MB).
Often loaded together with
Share of homepages with Cookiebot where the other tool is also among the five heaviest third parties.
- Google Tag Manager 60 %
- Google CDN 12 %
- Google/Doubleclick Ads 11 %
How to spot Cookiebot on your page
The banner script uc.js and cc.js load from consent.cookiebot.com, the settings for your domain group from consentcdn.cookiebot.com. Because the script sits in the head before other scripts, any delay here pushes back everything that follows. Its cost is mostly fixed per page view, so its share of the total matters most on otherwise lean pages.
How to reduce the impact of Cookiebot
- Prefer manual script blocking via data attributes over automatic blocking where your setup allows it; automatic blocking scans and rewrites scripts at runtime.
- Make sure the banner script is included only once.
- Check whether the banner text becomes the Largest Contentful Paint element on mobile and keep the banner compact.
Frequently asked questions
How can I load Cookiebot with less impact?
Prefer manual script blocking via data attributes over automatic blocking where your setup allows it; automatic blocking scans and rewrites scripts at runtime. Make sure the banner script is included only once.
Does Cookiebot affect Core Web Vitals?
As a consent banner, Cookiebot sits on the critical path. The banner is often the first large element a visitor sees, so it can become the LCP element itself, and if its script blocks rendering the actual content waits. A banner that pushes the page down instead of overlaying it causes layout shifts, and the consent check runs before other tags may start.
Method and sample: Third-Party Benchmark.