The online video files you played also exist here.
Please note: Firefox's temporary files are not like ie, and even the suffixes are random. Generally, it is to prevent virus infection or to expose the web pages you have visited (so it is so hidden and embarrassing).
The modification method is to enter "about:config" in the address bar of Firefox, thus opening the configuration page of Firefox. Right-click the mouse in the page and select "New → String", and an input dialog box will pop up. Enter browser.cache.disk.parent _ directory, and then enter the location of the new temporary folder after confirmation, such as E: \ Firefox temp, whatever you want.
Remember: don't put spaces in the name of the input folder!
If it is E: \ firefox temp, just restart firefox and open the webpage for the first time, and the E disk will create a new folder for firefox temp. Others and so on.