Which AI crawlers execute JavaScript?
Most do not, but the assumption is rarely tested. A page whose content is injected by script and which then requests a beacon URL turns this into an observation: any client that reaches the beacon has demonstrably executed JavaScript, and any client that fetches the page without the beacon demonstrably has not.
Measuring — the JS probe is live.
This matters more than it sounds. If a crawler does not run scripts, then a site that renders its content client-side is, from that crawler's perspective, close to empty — regardless of how much text a human sees.
It also explains why most analytics is blind here. Browser-based tracking only reports when scripts run, so a JavaScript tracker will faithfully report that no crawlers ever visit. That is not a measurement of crawler traffic; it is a measurement of script execution.
How this site measures it
One page carries its content inside a script rather than in the served HTML. The same script then requests a beacon URL carrying the identifier of that specific page view.
Reaching the beacon requires having executed the script. So the beacon request is direct evidence of JavaScript execution by that client, on that visit — not an inference from a user agent string or a capability table.
Clients that fetch the page and never the beacon produce the opposite evidence, equally recorded.
Why this page is the only one with scripts
Every other page here ships no JavaScript at all. Script execution is the variable under measurement, so it cannot also be a dependency of the measurement — a site that required scripts to be observed could only ever observe clients that run them.
Current state
The probe is live and recording. Results appear on the lab page as distinct user agents observed executing scripts. No general claim about any named crawler is made yet.
What the record shows today
No external client has ever executed the script on this site. The probe page has been fetched 10 times from outside; the beacon it contains has never fired for any of them.
This is a real result rather than a missing measurement — the mechanism works and has been verified with a browser. It means every external client that has fetched that page so far read the HTML and stopped there, which is what a crawler that does not render pages looks like.
Computed from the record at 2026-07-30 04:24:50 UTC. Every figure here is recomputed when the page is requested, so this section moves as the record does — week by week.