diagnostic · one of 36 Field data - what real visitors experienced - is the Pro half; the navigation reading is free.
Load timing
Where did the time go on this page load?
The browser records exactly how long each phase of a navigation took, and the number people usually quote - "it loads in two seconds" - hides which phase owns the two seconds. A slow TTFB is a server problem, a slow processing phase is a JavaScript problem, and the fix for one does nothing for the other.
Reach it Press ⌘ + K on any tab and type load timing. Ctrl + K on Windows and Linux
in the panel · this one is Pro
What this actually is
the real waterfall for this document, summarisedWhen a page is slow and nobody has established where. Run it on a fresh load: this is one load on one machine and the card says so, which is exactly why the field data beside it is worth having.
Asked about this diagnostic
4 of themWhy is one load not enough?
Because it is your machine, your connection and a warm or cold cache you did not choose. It is the right reading for finding which phase is slow and the wrong one for claiming a number.
What is the field data?
What real visitors to this origin experienced, which is the only measurement that answers "is this fast for people". It is the Pro capability inside this tool; the navigation reading is free and complete.
Does the origin get sent anywhere?
Only for the field-data request, and only when you ask for it. The navigation breakdown is read from your own browser and transmits nothing.
Why do the phases not add up to the total?
Because some of them overlap and some of them are zero on a reused connection. Each phase is reported as the browser recorded it rather than being scaled to fill a bar.
how to use load timing
- Reload the page, then open Load timing.
- Read which phase owns the time: a slow TTFB is a server problem, slow processing is a script problem.
- The card says this is one load on one machine, and it means it.
- Read the field data beside it before drawing a conclusion from a single sample.
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