How fast are the biggest Czech online stores: measuring 85 shops

We took the CzechCrunch and BizMachine Top 100 Czech online stores ranking and measured the home page of every shop with a .cz or .eu domain - 85 online stores in total. Speed through Google PageSpeed Insights, real visitor data from the Chrome UX Report, and AI readiness from robots.txt, the llms.txt file and how much content is in the HTML without JavaScript. We don't name individual online stores; this is about the overall picture.

Loading: 12 seconds in the lab, 1.7 for people

Lighthouse on mobile simulates a slower phone on a worse network, and in that simulation the main content loads in a median of 12 seconds. The median mobile score is 48 out of 100, and only one online store out of 81 measured gets 90+. Real visitors, however, see the main content in a median of 1.7 seconds, and 90% of online stores are within Google's limit of 2.5 seconds. Both are true at once: on an ordinary phone with a good signal it's fine, on an older phone or on a train it isn't.

Where it really drags: response to a click

Only 31% of online stores meet Core Web Vitals for real people. For 56 of the 58 that failed, INP is to blame - the time before the page reacts to a tap. The median is 244 ms, Google's limit is 200 ms. A customer taps a filter or a size and nothing happens for a moment. Response is slowed mainly by JavaScript: half of the online stores block the browser with scripts for more than half a second, and 63% of home pages are heavier than 3 MB.

AI crawlers: they let them in, but show them half

At least one AI crawler is blocked in robots.txt by 16% of online stores, and crawlers of AI search engines and assistants such as GPTBot or ClaudeBot by only 10%. So most of them want visibility in AI answers. But a crawler that doesn't run JavaScript sees only the HTML response - and in it, for the median online store, there is 57% of the text a person sees. 24% of online stores have an llms.txt file, and 70% have structured data in the HTML.

What this means for a smaller online store

These are the biggest shops on the market with their own development teams, and still most of them don't pass the limit for response time. A fast response to a click and content readable without JavaScript are not a question of budget, but of how the website is built. We'll measure the same metrics on your online store as part of a free website audit. The complete numbers and methodology are in the report Speed and AI readiness of Czech online stores in the Data section.