Knowledge base v2.13.0 · Community edition · data through 2 October 2026
Thing · Concept
Running a page's JavaScript in a headless Chrome so Google sees the content as a browser shows it.
Glossary · Rendering
Running a page's JavaScript in a browser engine to see what users see. Google renders with Chromium and indexes the rendered HTML.
Documented in
Google's robots meta tag specification says data-nosnippet may be extracted both before and after rendering, so the attribute should not be added to or removed from existing elements with JavaScript.
Google Search Central · Day 2 · Controlling indexing
Google's JavaScript SEO basics guide says that when Google encounters a noindex rule it may skip rendering and JavaScript execution, so using JavaScript to change or remove a noindex robots meta tag may not work as expected.
Google Search Central · Day 2 · Controlling indexing
Google's JavaScript SEO guide says Googlebot sends every page with a 200 HTTP status code to the rendering queue, whether or not it contains JavaScript, unless a robots meta tag or header tells Google not to index it, and Google uses the rendered HTML to index the page.
Google Search Central · Day 2 · Lightning session D: Rendering and JavaScript
Google says Googlebot and its Web Rendering Service identify resources that do not contribute to essential page content, such as reporting and error requests, and may not fetch them, so client-side analytics may not give a full or accurate picture of their activity.
Google Search Central · Day 2 · Lightning session D: Rendering and JavaScript
Google's JavaScript SEO basics guide says Googlebot extracts links twice, from the HTML response before rendering and again from the rendered HTML, so links injected with JavaScript can be found if they use crawlable <a href> markup.
Google Search Central · Day 2 · Lightning session D: Rendering and JavaScript
In Google's March 2023 SEO office hours, John Mueller said Google handles infinite scroll with viewport expansion, rendering a page like a very long phone, which is not very efficient and can miss content, so pagination links are strongly recommended.
Google Search Central (SEO office hours transcript, March 2023) · Day 2 · Lightning session D: Rendering and JavaScript
Google says its Web Rendering Service fetches the resources a page references through Googlebot, including JavaScript, CSS and XHR requests to APIs, but not images or videos.
Search Central blog (3 December 2024), Search Central blog (31 March 2026) · Day 2 · Lightning session D: Rendering and JavaScript
Google's JavaScript SEO basics says every page with a 200 status code is queued for rendering, whether or not it uses JavaScript, unless a robots meta tag or header says not to index it; for non-200 pages such as 404 error pages, rendering might be skipped.
Google Search Central · Day 2 · What is Google friendly JavaScript
Google's March 2023 SEO office hours say Google sees infinite-scroll content through viewport expansion, rendering a page like a very long phone, which is not particularly efficient and can miss infinite content.
Google Search Central (SEO office hours transcript, March 2023) · Day 2 · What is Google friendly JavaScript
For effects that need WebGL, which Googlebot does not support, Google's guide to fixing JavaScript problems suggests skipping the effect or prerendering it with server-side rendering so that the content is accessible to Googlebot.
Google Search Central · Day 2 · What is Google friendly JavaScript
Google's guide to fixing Search-related JavaScript problems says its Web Rendering Service keeps no state across page loads: local storage, session storage and HTTP cookies are cleared.
Google Search Central · Day 2 · What is Google friendly JavaScript
Google's guide to fixing Search-related JavaScript problems says the Web Rendering Service may ignore caching headers and so use outdated JavaScript or CSS, and recommends content fingerprinting, which puts a hash of the content in the file name, as in main.2bb85551.js.
Google Search Central · Day 2 · What is Google friendly JavaScript
Google's guide to how Search works says rendering happens during the crawl, and describes indexing as analysing a page's text, key tags and attributes such as title elements and alt attributes, images and videos, and deciding whether the page is a duplicate or the canonical.
Google Search Central · Day 2 · Finding the gold nuggets: structured data, media, and more!
Slide and stage claims that name it, the ones Google’s documentation does not cover first.
Google described the mission of its rendering as simply executing JavaScript, while the implementation is complex, expensive and difficult.
Erin Sparling · Day 2 · Lightning session D: Rendering and JavaScript
After the crawler has fetched a page, Google's rendering system executes it, checks that it loads properly and works out what it looks like at different sizes.
Erin Sparling · Day 2 · Lightning session D: Rendering and JavaScript
Google said its pipeline needs to ensure that content indexable without JavaScript can pass through without rendering, while content that appears only through JavaScript and CSS takes a longer rendering pass.
Erin Sparling · Day 2 · Lightning session D: Rendering and JavaScript
Switching JavaScript off and on in the browser gives a quick first impression of which content on a page depends on rendering.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
Unresolved placeholders caused by rendering timeouts are hard to catch because the problem moves around: it is not always the same page that is broken.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
To catch intermittent rendering problems, archive the full HTML and the resources of each page during a site audit and analyse them yourself, a community speaker advised.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
If a page keeps loading content indefinitely, not all of that content will be indexed, because Google's rendering does not go on forever (this passage of the recording is partly unclear).
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
Besides using Chrome DevTools more often, a community speaker advised checking rendering at scale with a modern crawler.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
Erin Sparling called URL fragments (the part of a URL after #) the next most common JavaScript issue seen, after rendering problems and blocked rendering.
Erin Sparling · Day 2 · What is Google friendly JavaScript
Google's indexing pipeline slide put a Processing stage between the crawler and the index and listed HTML parsing, rendering, deduplication and feature extraction above it, with feature extraction highlighted as the step of this talk.
Gary Illyes · Day 2 · Finding the gold nuggets: structured data, media, and more!
Gary Illyes said Google keeps saying it renders every URL on the internet and that he would say this is not true, though it is what he was told; he went on to say that Google's logs show the rendering queue cleared within weeks.
Gary Illyes · Day 3 · How long does it take to..?
According to Google's logs, everything in the rendering queue gets rendered within weeks.
Gary Illyes · Day 3 · How long does it take to..?
A Google pipeline slide placed processing between the crawler and the index and listed six processing steps: HTML parsing, rendering, deduplication, feature extraction, signal extraction and index selection.
Google renders pages in order to index what users see: its commitment to reflecting the user experience means understanding what people see when a page loads in a browser and surfacing that in Search.
Erin Sparling · Day 2 · Lightning session D: Rendering and JavaScript
Google's simple solution for the extra time of live page reads is to make JavaScript-generated content render quickly and efficiently, or to use server-side rendering.
Erin Sparling · Day 2 · Lightning session D: Rendering and JavaScript
A Google pipeline diagram ran from the crawl queue to the crawler, then through HTML parsing to processing, which passes pages to rendering and gets them back, and then to the index; rendering fetches its JavaScript and CSS through the crawler.
Erin Sparling · Day 2 · Lightning session D: Rendering and JavaScript
Although Google's pipeline diagram shows rendering as part of indexing, Google's rendering is a detached system, kept separate because rendering is time-consuming and computationally expensive.
Erin Sparling · Day 2 · Lightning session D: Rendering and JavaScript
In a navigation example, the main navigation was in the raw HTML and would survive a rendering failure, but the whole sub-navigation was built by JavaScript, so all of its links would be inaccessible to bots if rendering broke.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
Sites that create their content by rendering should have at least basic monitoring to check that the rendered pages come out right, a community speaker advised.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
Whatever is in the DOM at the moment Google's rendering finishes is what likely gets indexed.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
For rendering, what matters is whether content is present in the DOM, not whether it is visible on screen: hidden content can be indexed, absent content cannot.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
An Intersection Observer fires when the observed element enters the viewport, and the viewport Google renders with is tall, so content lazy-loaded this way can load during rendering.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
Disallowing a script folder such as /static/js/ or a generic /api/ folder in robots.txt can block the endpoints that supply a page's content, leaving blank modules and missing content after rendering.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
If an API folder must stay blocked in robots.txt, allow the endpoints that rendering needs, for example Disallow: /api/ together with Allow: /api/products/.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
On a product page whose data is fetched client-side, the rendering mistakes described can leave Google seeing no content at all while users still see the price and images.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
To find rendering issues, compare a page's raw source code with its rendered versions, including the rendered HTML that Google's testing tools show; the differences point to the problems.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
If JavaScript rendering fails, what Google indexes for a page differs from what the page shows once it is rendered.
Erin Sparling · Day 2 · What is Google friendly JavaScript
Erin Sparling named server-side or hybrid rendering, fallbacks and not leaving placeholders in the DOM, among other measures, as ways to guard against failed JavaScript rendering.
Erin Sparling · Day 2 · What is Google friendly JavaScript
For headless CMS content, Erin Sparling presented rendering on the server, not only in the browser, as a way to avoid indexing issues.
Erin Sparling · Day 2 · What is Google friendly JavaScript
Google estimated that rendering takes seconds when done right away and hours when the page waits in the queue, with an end point of days to weeks.
Never block a resource that a page needs for rendering with robots.txt, a community speaker said, calling this common sense.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
In Google's processing step, links are extracted from the HTML Google already has, before rendering, and the URLs found go back to the crawl queue.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
After processing, an indexable page is placed in Google's render queue to wait for rendering.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
Blocking JavaScript or API resources in robots.txt is a classic rendering mistake: if Google's renderer cannot fetch a resource, it cannot run it.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
Google renders nearly all of the web by replicating what a browser does, using a real browser's rendering engine.
Erin Sparling · Day 2 · What is Google friendly JavaScript
Content that is not in the final DOM after rendering cannot be seen by Google, so it cannot be indexed.
Erin Sparling · Day 2 · What is Google friendly JavaScript
Content loaded as elements enter the viewport, for example with an Intersection Observer, does load when Google renders a page, because Google's rendering viewport is very tall.
Erin Sparling · Day 2 · What is Google friendly JavaScript
WebGL does not work well in Google's rendering: a WebGL shader that makes a page look like it is underwater will not be applied when Google renders the page.
Erin Sparling · Day 2 · What is Google friendly JavaScript
Erin Sparling recommended differential serving and polyfills to keep a site compatible with Google's rendering engine where it lacks a browser feature.
Erin Sparling · Day 2 · What is Google friendly JavaScript
Google framed rendering historically: when Google started, most of the web was plain, semantic HTML it could extract directly, but the modern web is built with JavaScript and much content is generated by JavaScript, so Google had to adapt.
Erin Sparling · Day 2 · Lightning session D: Rendering and JavaScript
After Google's opener, Lightning session D had three community talks: rendering and JavaScript execution blind spots (Sören Bendig), debugging JavaScript rendering for Search (Rebecca Yu) and virtualizing the browser (Natalia Venditto).
Erin Sparling · Day 2 · Lightning session D: Rendering and JavaScript
Many SEOs still treat everything beyond the raw HTML as the developers' business, but developers often do not handle rendering problems, a community speaker warned.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
The first rendering blind spot a community speaker showed was content changes: text, images and recommendations that differ between the raw HTML and the rendered page, illustrated by a shop page whose rendered version had a whole extra section.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
One site that builds its whole content by rendering also rendered its meta description with HTML tags inside it, which makes no sense and points to a flawed process.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
A community speaker summarised five rendering blind spots to check: content and markup changes, invisible links, rendering timeouts, Content Security Policy and blocked resources.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
Because even established brands have these rendering problems and every modern website uses a lot of JavaScript, a community speaker argued that most sites probably have them too and that ignoring rendering is reckless.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
The second community lightning talk of the rendering block covered debugging JavaScript rendering for Search: how Google renders pages, a step-by-step check, four common mistakes and a worked product page example.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
A community speaker listed four common but often overlooked JavaScript rendering mistakes: non-crawlable link markup, error pages that return HTTP 200 in single-page apps, content behind user interaction, and JavaScript or API resources blocked in robots.txt.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
A community speaker called not hiding content behind user interaction the most important of the four JavaScript rendering mistakes.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
A community speaker summed up JavaScript rendering issues as cases where search engines cannot execute, access or trigger the code needed to display a page's core content.
Rebecca Yu · Day 2 · Lightning session D: Rendering and JavaScript
Websites that rely heavily on JavaScript and rendering have common blind spots, because these features often break in subtle ways, a community speaker said.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
None of the rendering problems a community speaker showed from established brands' sites had been fixed promptly: some were fixed by the time of the talk and some were still live.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
A rendering failure such as a Content Security Policy blocking a video on a landing page that explains how to open a business account could have a drastic impact for a purely online business, a community speaker warned.
Sören Bendig · Day 2 · Lightning session D: Rendering and JavaScript
When Search Console reports that content is not rendering, Erin Sparling suggested putting AI agents on the problem, but only after doing your own due diligence.
Erin Sparling · Day 2 · What is Google friendly JavaScript
Google's redirects guide says Google Search follows JavaScript location redirects only after rendering, may never see one if rendering fails, and should be used only when server-side or meta refresh redirects are impossible; its site move guide asks for server-side permanent redirects (301 or 308) where technically possible. The JavaScript in Google's own migration was a fallback ('my only option'), not a pattern to copy.
Ibrahim Anjro · Day 1 · Q&A
Put rel=canonical and hreflang link elements in the head of the HTML the server sends, not only in JavaScript-rendered HTML, so Google can read them during HTML parsing without depending on rendering.
Ibrahim Anjro · Day 2 · How is HTML interpreted
Ship robots rules in the HTML the server sends and never rely on JavaScript to lift a noindex: Google may skip rendering a page that arrives with noindex, so the page can stay out of the index even if a script removes the tag later.
Ibrahim Anjro · Day 2 · Controlling indexing
On stage the rule was absolute (Google won't even process the JavaScript of a page served with noindex), while Google's guide says only that it may skip rendering; either way, a noindex in the served HTML must never be one that JavaScript is expected to lift.
Ibrahim Anjro · Day 2 · Controlling indexing
The stage remark that content indexable without JavaScript can pass through without rendering does not mean such pages skip rendering, because Google's guide queues every 200 page for rendering; read it as: content already in the raw HTML does not depend on the slower rendering pass.
Ibrahim Anjro · Day 2 · Lightning session D: Rendering and JavaScript
Put everything indexing depends on (title, meta description, canonical, robots meta tag, main text and links) in the raw HTML so it is available without rendering, let JavaScript add enhancements only, and check the rendered HTML in URL Inspection for the rest.
Ibrahim Anjro · Day 2 · Lightning session D: Rendering and JavaScript
Check rendering per template rather than per URL: inspect one URL of each page type (product, category, article) in URL Inspection and confirm that the main content, prices and internal links appear in the rendered HTML.
Ibrahim Anjro · Day 2 · Lightning session D: Rendering and JavaScript
Because Web Fragments monkey-patches core browser APIs such as document, history and location, test pages that use it in Google's rendering (the rendered HTML in Search Console's URL Inspection tool or the Rich Results Test), not only in a normal desktop browser.
Ibrahim Anjro · Day 2 · Lightning session D: Rendering and JavaScript
Check robots.txt for Disallow rules covering JavaScript bundles, build folders or API endpoints the page calls while rendering, including on separate API or CDN hostnames with their own robots.txt, then confirm in URL Inspection's live test that the rendered HTML contains the main content.
Ibrahim Anjro · Day 2 · What is Google friendly JavaScript
With a headless CMS, choose the rendering per template before launch (server-rendered or pre-rendered for pages that must rank), and make any agent-built test suite assert that the main content and <a href> links are present in the rendered HTML.
Ibrahim Anjro · Day 2 · What is Google friendly JavaScript
Put critical content, links and meta tags in the server HTML: content that needs JavaScript reaches indexing only after rendering, usually within hours but sometimes weeks, and even Google's own speaker doubted that every URL gets rendered.
Ibrahim Anjro · Day 3 · How long does it take to..?
The stage doubt that every URL gets rendered sits beside Google's JavaScript guide, which says every page with a 200 status is queued for rendering unless a robots rule blocks indexing: queued is not the same as rendered, so do not rely on rendering for critical content.
Ibrahim Anjro · Day 3 · How long does it take to..?
Kit items about Rendering: their own words name it, or several of the claims they rest on do.
Server-render the main content and everything indexing depends on (SSR, static generation or hybrid)
Rests on 11 claims, 5 of them naming Rendering; its own words name Rendering
Make rendering robust: no slow API dependencies and no unresolved placeholders
Rests on 8 claims, 5 of them naming Rendering; its own words name Rendering
Run recurring rendering checks: raw versus rendered HTML, placeholders and console errors
Rests on 7 claims, 4 of them naming Rendering; its own words name Rendering
Do not add, change or remove robots meta tags with JavaScript
Rests on 9 claims, 4 of them naming Rendering; its own words name Rendering
Do not block JavaScript, CSS or API endpoints that pages need for rendering in robots.txt
Rests on 7 claims, 3 of them naming Rendering; its own words name Rendering
Give every indexable page a unique, descriptive title element in the server HTML
Rests on 7 claims, 2 of them naming Rendering
Rests on 7 claims, 2 of them naming Rendering
Have all indexable content in the DOM after load, without clicks, typing or scrolling
Rests on 8 claims, 2 of them naming Rendering
Lazy-load with native lazy loading or an IntersectionObserver, never with scroll events
Rests on 6 claims, 2 of them naming Rendering; its own words name Rendering
Feature-detect permission-based APIs and WebGL, and render the content without them
Rests on 5 claims, 2 of them naming Rendering
Use permanent server-side redirects (301 or 308) for moved URLs, straight to the final URL
Rests on 10 claims, 1 of them naming Rendering; its own words name Rendering
Use data-nosnippet on a span, div or section to keep one detail out of snippets
Rests on 6 claims, 1 of them naming Rendering; its own words name Rendering
Make JavaScript-generated content render quickly
Rests on 5 claims, 1 of them naming Rendering; its own words name Rendering
Also inglossary terms Render queue, Rendering, Raw HTML and rendered HTML, Viewport expansion
Things named in the same claim, with the number of claims they share.