Knowledge base v2.13.0 · Community edition · data through 2 October 2026
Topic · Rendering and JavaScript
Day 2 confirms Day 1's point that Google's crawlers do not click and adds that they do not scroll either: content that loads only after a click or a scroll is not in the DOM when Google renders the page, so it cannot be indexed. What counts is presence in the DOM, not visibility: tab or accordion content hidden with CSS or the hidden attribute can be indexed, while tab content fetched from an API on click does not exist for Google. Instead of scrolling, Google renders in a tall viewport, about 10,000 pixels according to Google's speaker (a figure not in the documentation, which calls it viewport expansion and warns it can miss infinite content), so content loaded when an element enters the viewport, for example with an Intersection Observer, loads while scroll-event listeners never run. For infinite scroll, Google's lazy-loading guide asks for paginated loading, with a persistent URL for each chunk, sequential links between them and the History API updating the displayed URL, a concrete pattern to go with Day 1's caution that 'load more' pagination is risky.
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Content that loads only after a user action such as a click or a scroll is not in the DOM while Google renders the page, so Google cannot index it.
Speaker Rebecca YuIn Day 2, 10:40 · Lightning session D: Rendering and JavaScriptEvidence slide photo, transcript
Used byrequirement DEV-REN-02
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.
“Not visible versus hidden. Present versus absent in the DOM.”
Wording checked against the slide or recording
Speaker Rebecca YuIn Day 2, 10:40 · Lightning session D: Rendering and JavaScriptEvidence slide photo
Used byrequirement DEV-REN-02
Lazy loading triggered by a scroll event listener, such as window.addEventListener('scroll', loadMoreProducts), never runs for Googlebot because Googlebot does not scroll.
“Googlebot doesn't scroll. Never runs.”
Wording checked against the slide or recording
Speaker Rebecca YuIn Day 2, 10:40 · Lightning session D: Rendering and JavaScriptEvidence slide photo, transcript
Used byrequirement DEV-REN-03glossary term Lazy loading
Lazy loading should be triggered by an Intersection Observer that watches a sentinel element instead of by a scroll event listener.
Speaker Rebecca YuIn Day 2, 10:40 · Lightning session D: Rendering and JavaScriptEvidence slide photo, transcript
Used byrequirement DEV-REN-03glossary term Lazy loading
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.
“Fires on viewport entry. Viewport is tall.”
Wording checked against the slide or recording
Speaker Rebecca YuIn Day 2, 10:40 · Lightning session D: Rendering and JavaScriptEvidence slide photo
Used byrequirement DEV-REN-03
Tab or accordion content fetched from an API only when a user clicks the tab, as in tab.onclick = () => fetch('/api/specs'), does not exist for Google until someone clicks.
“Doesn't exist until someone clicks”
Wording checked against the slide or recording
Speaker Rebecca YuIn Day 2, 10:40 · Lightning session D: Rendering and JavaScriptEvidence slide photo
Used byrequirement DEV-REN-02
Tab and accordion content should be in the DOM from the start and only hidden with CSS or the hidden attribute; Google indexes such hidden content.
“CSS-hidden is fine. Google indexes it.”
Wording checked against the slide or recording
Speaker Rebecca YuIn Day 2, 10:40 · Lightning session D: Rendering and JavaScriptEvidence slide photo, transcript
Used byrequirement DEV-REN-02
When checking which links bots can see, keep in mind that the rendered HTML can change with user actions, a community speaker cautioned.
Speaker Sören BendigIn Day 2, 10:40 · Lightning session D: Rendering and JavaScriptEvidence transcript
A community speaker called not hiding content behind user interaction the most important of the four JavaScript rendering mistakes.
Speaker Rebecca YuIn Day 2, 10:40 · Lightning session D: Rendering and JavaScriptEvidence transcript
In the speaker's product page example, three of the mistakes combine: product links behind onclick handlers keep the product detail pages hidden, the product API is blocked in robots.txt, and some content waits for a user interaction.
Speaker Rebecca YuIn Day 2, 10:40 · Lightning session D: Rendering and JavaScriptEvidence transcript
Content that loads only when a user clicks an element is not supported in the way Google renders pages for indexing.
Speaker Erin SparlingIn Day 2, 11:15 · What is Google friendly JavaScriptEvidence transcript
Used byrequirement DEV-REN-02glossary term Lazy loading
Google does not scroll a page when it renders it for indexing, so content that infinite scroll loads on scroll-depth triggers works for users but is never loaded for Google.
Speaker Erin SparlingIn Day 2, 11:15 · What is Google friendly JavaScriptEvidence slide photo, transcript
Used byrequirements DEV-REN-03, DEV-URL-07
Instead of scrolling, Google renders a page in a very tall viewport, around 10,000 pixels high.
“it renders it in a very tall viewport. Specifically, around 10,000 pixels is what the viewport gets rendered as.”
Speaker Erin SparlingIn Day 2, 11:15 · What is Google friendly JavaScriptEvidence slide photo, transcript
Used byrequirements DEV-REN-03, DEV-URL-07glossary term Viewport expansion
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.
Speaker Erin SparlingIn Day 2, 11:15 · What is Google friendly JavaScriptEvidence transcript
Used byrequirement DEV-REN-03
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.
“this is done through a technique called "viewport expansion", where we render a page like a very long phone.”
Publisher Google Search Central (SEO office hours transcript, March 2023)Annotates Day 2, 10:40 · Lightning session D: Rendering and 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.
“a technique called "viewport expansion", where we render a page like a very long phone”
Publisher Google Search Central (SEO office hours transcript, March 2023)Annotates Day 2, 11:15 · What is Google friendly JavaScript
Used byrequirement DEV-URL-07glossary term Viewport expansion
To make infinite scroll indexable, Google's lazy-loading guide says to support paginated loading: give each chunk its own persistent, unique URL, link sequentially to those URLs, and update the displayed URL with the History API when a new chunk becomes the main visible element.
Publisher Google Search CentralAnnotates Day 2, 11:15 · What is Google friendly JavaScript
Used byrequirement DEV-URL-07
Audit tabs, accordions and 'load more' lists for content fetched on click or scroll: put tab content in the initial DOM and hide it with CSS, trigger lazy loading with an Intersection Observer, and give long lists paginated URLs linked with <a href>.
Author Ibrahim AnjroAnnotates Day 2, 10:40 · Lightning session D: Rendering and JavaScript
Treat the 10,000-pixel viewport as a safety margin, not a target: load lazy content when it enters the viewport (Intersection Observer or native lazy loading, never scroll listeners), and give infinite-scroll content paginated URLs linked with <a href> so anything below the first rendered screen stays reachable.
Author Ibrahim AnjroAnnotates Day 2, 11:15 · What is Google friendly JavaScript
Content that loads only after a user action such as a click or a scroll is not in the DOM while Google renders the page, so Google cannot index it.
Google's crawlers do not click buttons. Each page in a series needs its own URL and an <a href> link to the next page, should not use page 1 as its canonical, and rel=next and rel=prev are no longer used.
Lazy loading triggered by a scroll event listener, such as window.addEventListener('scroll', loadMoreProducts), never runs for Googlebot because Googlebot does not scroll.
Tab or accordion content fetched from an API only when a user clicks the tab, as in tab.onclick = () => fetch('/api/specs'), does not exist for Google until someone clicks.
Google's crawlers do not click buttons. Each page in a series needs its own URL and an <a href> link to the next page, should not use page 1 as its canonical, and rel=next and rel=prev are no longer used.
Content that loads only when a user clicks an element is not supported in the way Google renders pages for indexing.
Google's crawlers do not click buttons. Each page in a series needs its own URL and an <a href> link to the next page, should not use page 1 as its canonical, and rel=next and rel=prev are no longer used.
Google does not scroll a page when it renders it for indexing, so content that infinite scroll loads on scroll-depth triggers works for users but is never loaded for Google.
Google does not scroll a page when it renders it for indexing, so content that infinite scroll loads on scroll-depth triggers works for users but is never loaded for Google.
Instead of scrolling, Google renders a page in a very tall viewport, around 10,000 pixels high.
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.
To make infinite scroll indexable, Google's lazy-loading guide says to support paginated loading: give each chunk its own persistent, unique URL, link sequentially to those URLs, and update the displayed URL with the History API when a new chunk becomes the main visible element.
Google's crawlers do not click buttons. Each page in a series needs its own URL and an <a href> link to the next page, should not use page 1 as its canonical, and rel=next and rel=prev are no longer used.
Content inside tabs, for example separate tabs for a product description and a manufacturer description, might be part of a page's main content.
Tab and accordion content should be in the DOM from the start and only hidden with CSS or the hidden attribute; Google indexes such hidden content.
Content that loads only when a user clicks an element is not supported in the way Google renders pages for indexing.
Content that loads only after a user action such as a click or a scroll is not in the DOM while Google renders the page, so Google cannot index it.
Google does not scroll a page when it renders it for indexing, so content that infinite scroll loads on scroll-depth triggers works for users but is never loaded for Google.
Lazy loading triggered by a scroll event listener, such as window.addEventListener('scroll', loadMoreProducts), never runs for Googlebot because Googlebot does not scroll.
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.
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.
Lazy-load with native lazy loading or an IntersectionObserver, never with scroll events
Rests on 6 claims, 6 of them in this topic
Have all indexable content in the DOM after load, without clicks, typing or scrolling
Rests on 8 claims, 5 of them in this topic
Back infinite scroll and load-more buttons with paginated URLs
Rests on 6 claims, 4 of them in this topic