Maximum file size
When you want to make sure your curl command line will not try to download a too-large file, you can instruct curl to stop before doing that, if it knows the size before the transfer starts! Maybe that would use too much bandwidth, take too long time or you do not have enough space on your hard drive:
curl --max-filesize 100000 https://example.com/
Give curl the largest download you will accept in number of bytes and if curl can figure out the size before the transfer starts it will abort before trying to download something larger.
There are many situations in which curl cannot figure out the size at the time the transfer starts and this option will not affect those transfers, even if they may end up larger than the specified amount.