Autosave was first introduced in WordPress 2.1 in January of 2007. The default AUTOSAVE_INTERVAL in WordPress is 60 seconds, but we bump that up to 120 seconds, or 2 minutes. In other words, if you have an unsaved post or page in the WordPress administration area, the autosave interval will kick in after 2 minutes to save it automatically for you. There's 1 autosave version of a post or page, and it's separate from other post revisions. In our experience, automatic saving that's too frequent can disrupt workflow by unexpectedly taking control of a user's system while the automatic save is performed; a very long AUTOSAVE_INTERVAL completely removes an important safety net that can allow you to recover important work. We previously had the AUTOSAVE_INTERVAL set much higher, but our testing showed there wasn't a noticeable performance hit to using a lower value. Therefore, we lowered it to take advantage of the content protection that autosave provides. We always recommend that you save your work when you think it's the right time to do so, but if that doesn't happen, the AUTOSAVE_INTERVAL might provide some protection.