Fetch & Render

What fetching and rendering actually mean

When a crawler visits a URL it first makes an ordinary HTTP request and receives a status code, headers and an HTML document. That document is the raw response. Many sites then rely on JavaScript to build the page that people see: client-side frameworks fetch data, insert content and sometimes rewrite the title or canonical tag. The page after that JavaScript has run is the rendered DOM.

Google renders pages with an evergreen version of Chromium, but rendering happens in a separate queue after the initial crawl, and Google has said that a page with noindex in its raw HTML may never be rendered at all. Bing renders too. Many AI crawlers, including those that fetch pages to answer questions, read only the raw HTML. So the safest page is one where the raw response already carries the content and signals you care about.

How this tool works

Our server requests the URL using the user agent you choose, follows up to five redirects, and checks every hop against private network ranges before connecting. The response comes back to your browser, which parses it without executing any of its scripts. Every panel is labelled with its source, so you always know whether you are looking at a raw response or a real render.

When the site owner has connected Cloudflare Browser Rendering, the tool also loads the page in headless Chromium with a matching viewport, waits for network activity to settle, and returns the resulting HTML and a screenshot. You then get a side-by-side comparison and findings such as content that only appears after JavaScript, links that only exist in the rendered DOM, or a canonical tag that JavaScript changed.

Choosing a request profile

• Googlebot Smartphone is the profile Google uses for most crawling, because Google indexes the mobile version of pages.
• Googlebot Desktop and Bingbot are useful when a site serves different HTML by device or crawler.
• GPTBot, OAI-SearchBot, ChatGPT-User, ClaudeBot, Claude-User, PerplexityBot and Perplexity-User show whether a site answers AI crawlers differently, for example with a block page or a challenge.
• Chrome on desktop or Android is the baseline an ordinary visitor would receive.

Tick the desktop and mobile option to fetch the page twice and compare the two versions.

Reading the raw versus rendered comparison

A large gap in word count between raw and rendered HTML means the main content depends on JavaScript. That is acceptable for Google if rendering succeeds, but it delays indexing, exposes you to rendering failures and hides the content from crawlers that do not render. Server-side rendering, static generation or pre-rendering solve it.

Differences in title, canonical or robots directives are more serious. Google documents that changing the canonical with JavaScript sends conflicting signals, and that robots meta tags should not rely on JavaScript. Fix these in the server HTML first.

Blocked resources

If robots.txt disallows the CSS or JavaScript a page needs, Google renders a broken version of it. The resource check lists every script and stylesheet in the raw HTML, fetches each host robots.txt, and reports whether Googlebot may fetch them. The rendering service does not report which requests a crawler would have been refused, so this check is the reliable way to find them.