diagnostic · one of 50 free, no counter
Network lab
What does this page do when a request fails or takes too long?
Every page is written on a fast connection that never drops, and the first time anybody sees its error state is when a customer does. This wraps the page's own fetch and XMLHttpRequest so they fail the way a dropped connection fails, or wait half a second, a second and a half or three seconds before they go out, and counts what it caught - so the banner, the spinner or the blank table that follows is something you looked at on purpose.
Reach it Press ⌘ + K on any tab and type network lab. Ctrl + K on Windows and Linux
in the panel · free, no counter
What this actually is
make fetch and xhr calls fail or wait to see how the page copes; delays are proBefore shipping a view that loads its data over fetch, when a bug report says the page went blank on a train, or when checking that a retry button retries and a stale list says it is stale. Reach for devtools throttling instead when images, scripts or fonts are the question - this does not touch them.
Asked about this diagnostic
3 of themIs this the same as devtools' Offline and throttling?
No, and the difference is the point of both. Devtools throttles the browser's whole network stack, images and fonts included. This changes two functions inside the page - fetch and XMLHttpRequest - so it tests how the page's own code handles a failed or slow call, and nothing else is affected. An image that fails to load is not something this can show.
Why did a request on the page still succeed while it was on?
Either it was not fetch or XHR - an image, a script, a stylesheet, a WebSocket, a beacon - or it was answered by a service worker or the HTTP cache, or it was already in flight when you switched. The panel says this beside the controls, because a test that quietly missed half the traffic would read as a page that copes.
Does anything stay changed after I turn it off?
No. The wrapper is installed in the page and removed by Turn off, by leaving the tool and by closing the panel, and a reload starts the page without it. Nothing is stored and the list of caught requests, cut at the path, never leaves the panel.
how to use network lab
- Open Network lab on the page, before the action that loads data.
- Choose Offline, or one of the delays, and use the page as a visitor would.
- Read what the page did with it, and the requests counted as failed or delayed.
- Press Turn off - or leave the tool - and the original fetch and XHR are back.
101 of these · no host permissions · three free audits