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RankBrain

Page Speed Test

Times server requests and sampled resources; adds browser paint measurements when capacity allows.

We load the page for you. Our server fetches the public address you enter and reads the response. Nothing you enter is stored. One step loads the page in a real browser on our side. Free, no account.

Finding the problem is the first half.

RankBrain applies the code-side fixes: deferred scripts, image dimensions, cache headers, lazy loading.

RankBrain works on websites built in code, through the AI tool you already use (Cursor, Claude Code, Codex, ChatGPT).

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How it works

Your page feels slow and you do not know which file is to blame. This test times the request from our server, reads a bounded sample of stylesheets, scripts, images and fonts referenced by the HTML, and when capacity allows loads the page in a real Chrome browser. You see paint times, layout shift and each file's size on the wire.

  1. 1

    Our server times the request itself: DNS, connection, TLS handshake and time to first byte, as the median of three requests.

  2. 2

    It then downloads a bounded sample of referenced stylesheets, scripts, images and fonts, recording transfer size, compression and cache lifetime.

  3. 3

    When capacity allows, the page is also loaded in a real Chrome browser on our side. That gives the first and largest contentful paint, layout shift and the full list of requests, including the ones scripts make.

What it does not do

  • The browser run happens in a data centre on a fast connection. Visitors on other devices and connections may see different numbers; use the results to compare before and after, not as a measurement of every visitor's experience.

  • Real-user data (the Core Web Vitals Google uses) only exists for sites with enough Chrome visitors and is reported in Search Console.

  • The real-browser run has a daily capacity. When it is used up, the server measurements still run and the page says which part is missing.

When a source is busy or a site does not answer, this tool says so. It never fills the gap with a guess.

Questions

Why is the speed number better than what my visitors see?

The browser run happens in a data centre on a fast connection, so visitors on other devices and connections may see different numbers. Use the results to compare one version of a page against another, not as what a customer experiences. The server timings and the file list still show what changed between two runs.

Which files are making my page heavy?

The test downloads a bounded sample of stylesheets, scripts, images and fonts referenced by the HTML and records transfer size, compression and cache lifetime. Look for the few large files and for files served without compression or with short cache lifetimes. Start with the scripts and stylesheets in the head: render-blocking resources can delay the first paint.

Can this test show the Core Web Vitals Google uses?

No. Aggregated Chrome field data needs enough eligible visits; Google reports it in Search Console and other CrUX-based tools. This test measures a single lab load in Chrome, plus the server timings. Core Web Vitals come from your visitors' actual devices, so treat this as a way to find and fix what is heavy, then watch Search Console for the field data.

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