SEO Browserthe crawler's-eye view

JavaScript SEO checker

Find content that only exists after JavaScript.

Fetch the raw source, then the rendered DOM, and diff them. Words and links present only after rendering are the ones a source-only crawl can miss.

The check reports a JS-injected proportion and a separate SEO-impact severity using the published thresholds below.

SOURCE vs RENDERED ///
Fetch as
JavaScript

No signup. Usually under 10 seconds. Your URL is submitted by POST, never written to disk or a database, and never logged by the crawler. It is processed in memory only for this one request, then discarded.

Advanced settings

Public pages only — the analyzer accepts http and https URLs on ports 80 and 443, follows up to five redirects, and caps the fetched response at 2 MB. Private, loopback, and cloud-metadata addresses are refused.

THRESHOLDS

How severity is scored.

JS-injected proportion is the share of the rendered word count that is not present in the raw source. The severity bands are fixed and published so a result is reproducible.

0%None

No JavaScript-dependent content — the rendered DOM matches the source, so it is fully visible to a source-only crawler.

< 10%Low

Under 10% of content appears only after JavaScript runs.

10–40%Medium

10–40% of content depends on JavaScript. Confirm crawlers can render it.

> 40%High

Over 40% of content depends on JavaScript. A source-only crawl sees little of it.

Honest limit: rendering here is one Chromium pass with a bounded timeout, and — for safety — it executes only scripts and styles served from the page's own host; cross-origin JavaScript and CSS are blocked. Sites that depend on third-party origins will render less completely here than in a full browser. Google's rendering can also differ in timing and resource budget. Treat a clean result as a strong signal, not a guarantee — confirm anything critical with Rich Results Test or URL Inspection.