Yandex can execute JavaScript when crawling, and the console lets you decide whether it should. The setting lives under Indexing → JavaScript page rendering, still in beta.
The three options
The default is at the bot’s discretion: the robot decides for itself, and Yandex describes how — it may compare the quality and completeness of the content with and without JavaScript, and load whichever version is likely to be more useful to the visitor. The alternatives are to require rendering or to forbid it.
When to forbid it
Yandex gives one clear instruction: prohibit rendering if the site implements SSR or pre-rendering. If the server already delivers complete HTML, executing scripts adds nothing and consumes crawl resources on both sides. Note the warning that comes with rendering in general — it can create additional load on your server.
Delayed content
For sites where content arrives late, Yandex supports a signalling object: create window.YandexRotorSetting so that it is processed before the DOMContentLoaded event, with WaiterEnabled set to indicate that the robot should wait. Registering it after that event does nothing — the robot has already decided.
The order of preference
Server-side rendering first, rendering-on-demand second, and the waiting object only where neither is possible. A page whose content depends on a script executing correctly is a page whose indexing depends on a process with far more failure modes than serving HTML — and Yandex’s own guidance elsewhere is unambiguous that what should rank must be present in the HTML immediately on request.
Checking the result
The JavaScript rendering tool checks individual URLs and shows what survives rendering; the ordinary page check shows the raw response. Comparing the two is the fastest way to see exactly which content depends on scripts — and therefore which content is at risk.
Cómo lo aplicamos
We treat this as a diagnostic before treating it as a setting: run the same URL through the plain page check and the rendering tool, and the difference is the content that only exists if a script runs. For clients with SSR we switch rendering off as Yandex recommends. The DOMContentLoaded timing on the waiter object is the detail developers get wrong, and it fails silently.
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