Warp Timer
The Warp Timer makes scripts check whether they are stuck in a long or infinite loop and drop to a low frame rate instead of freezing the whole project until the loop finishes. This prevents most "the project hung" crashes, but it has a real performance cost, so it is only on by default in the editor, not in the player. Toggle it in the editor settings or with the stuck URL parameter (also accepted as warp_timer).
As a demonstration, consider a project with an infinite loop inside a "run without screen refresh" block. With the Warp Timer on, the project keeps rendering at a low frame rate (a couple of frames per second). With it off, the script never yields and the project appears frozen.
Warp Timer was previously called "Stuck Checking".