Code to Disable Autosave in WordPress through Config File

/* Disable Autosave in WordPress */
define('AUTOSAVE_INTERVAL', 86400);

By default, WordPress autosaves pages and posts every one minute (60 seconds). You can also change that timing interval. However, if you want to disable autosave completely, add the above code in the wp-config.php file in the public_html folder.

This code will technically wont disable the feature, but it will extend the autosaving interval from 60 seconds to 1 day (86400 seconds)

It is also possible to disable autosave through a code to functions.php. But, it will only support the classic editor. For Gutenberg, you can achieve this through plugin. Please visit, Code to Disable Autosave for Classic Editor in WordPress for more details.