Blink (a.k.a. LagSwitch) is a Minecraft hack that temporarily stops the client from sending motion packets to the server, which makes it look to other players as if the user is standing still.

When Blink is turned off, the suspended motion packets are sent to the server all at once, making it look like the user suddenly teleports to their real location.

If Blink is cancelled instead, the suspended packets are simply deleted and the player is teleported back to their old position. This allows the user to “undo” a few seconds of movement. This can be very useful for parkour games, allowing the user to undo a failed jump.

There is a limit to how far the user can Blink at once, which is why Blink includes a counter for how many milliseconds have been “blinked” so far. The exact limit depends on the server and the user's internet connection. Generally, more than a few seconds of Blink-ing are not possible.

Blink often bypasses AntiCheat plugins, as players on a slow internet connection can teleport around in the same way as Blink hackers, through no fault of their own.

If a server tries to prevent Blink hacks, anything they do to the hackers also happens to any innocent players with slow enough internet. For this reason, most server admins decide not to block Blink hacks.

The Limit slider can be useful for simulating a slow internet connection.