lagcheck — can I play right now?

Your group — add and remove friends here

1 · Ask them for a code

They open lagcheck.com on their own device and run the check. It gives them a code to send you — nothing is collected about them, and nothing leaves their browser unless they choose to paste it.

2 · Paste a code they sent back

Or add someone without a code

Enough to tell you whether their provider is down or their region is affected — but they can't be ranked as a host until they run a check.

One place. Everything here stays in your browser — never sent anywhere, never stored on a server, and nothing is ever looked up about anyone. It's remembered between visits, and it's yours to delete.

Host picker Who should run the game tonight

Your check

Set it by hand

Where you are Upload 18 Mbps Jitter 4 ms Under load 22 ms Your plan (download) Provider

Who can be ranked

What these numbers mean

Upload: How fast you can push data out, measured over four connections at once to the nearest Cloudflare edge. This reads lower than Speedtest on purpose. Speedtest servers are often hosted by your own ISP, so they measure the line to your provider's doorstep. This measures a real internet destination — further away, and harder. For hosting, it's the more useful of the two. We also stop at a data cap, so on a fast line this is a floor, not a ceiling.
Ping: Round trip to that same edge. Jitter is how much it wobbles, and steadiness matters more than speed — a rock-solid 40 ms plays better than a 20 ms that jumps around.
Under load: The one that decides hosting. We ping while saturating your upload, because that's what hosting does: the game pushes to everyone at once. Under 60 ms of added delay is fine. Over 150 ms and the game stutters for everyone else no matter how good your idle ping looks. This is bufferbloat, and no plan speed ever tells you about it.
Provider: The network your traffic actually enters, read from the connection itself. That's the registered operator, which isn't always the brand on your bill.

A browser can time HTTP requests but can't measure UDP packet loss the way a game engine does. Treat all of this as a strong indicator, not a netgraph.

Ping is estimated from distance, so treat it as a strong indicator rather than a measurement. Only matters for games where one person actually hosts — anything on dedicated servers, pick the server region instead.