Why it matters
In single-page apps the server often returns the app with 200 for every URL and the front-end router shows a "not found" view, so no error is reported. When a server-side 404 is impractical, Google documents two fallbacks: a JavaScript redirect to a URL that returns 404, or a noindex robots meta tag added with JavaScript.
How to meet it
Prefer the server: route known paths, look up dynamic ones such as product slugs, and send the app shell with 404 for everything else. Otherwise, in the client, redirect error views to a URL the server answers with 404, or inject <meta name="robots" content="noindex"> on error views.
How to test it
curl -I on a made-up deep URL returns 404, or the rendered HTML in URL Inspection shows the redirect or the noindex; the Page indexing report shows no soft 404s on app routes.
How Regensbot covers it
Decided automatically once Regensbot renders your pages.
Headless Chromium renders the page on an isolated render service, and the raw and the rendered HTML run through the same parsers.
Sources
Google documents02
- 01Understand the JavaScript SEO basicsGoogle Search Central (opens in a new tab)
- 02Fix Search-related JavaScript problemsGoogle Search Central (opens in a new tab)
Claims in the knowledge base07
- D2-C190ConfirmedLightning session D: Rendering and JavaScriptSaid on stage
- D2-C291ConfirmedWhat is Google friendly JavaScriptSaid on stage
- D2-C264ConfirmedWhat is Google friendly JavaScriptShown on screen
- D2-C192SourceLightning session D: Rendering and JavaScriptGoogle's documentation
- D2-C294SourceWhat is Google friendly JavaScriptGoogle's documentation
- D2-C191ConsistentLightning session D: Rendering and JavaScriptSaid on stage
- D2-C295n/aWhat is Google friendly JavaScriptThe author's interpretation
Claim IDs refer to the Search Central Live 2026 knowledge base. The knowledge base (opens in a new tab)
- Confirmed
- Google's documentation states the same thing.
- Consistent
- Google's documentation supports it without stating it.
- Source
- The claim is the cited document itself.
- n/a
- Nothing to verify: a quotation, framing, opinion or analysis.