How to make sure testers don't see old cached version?

I frequently update my game and upload the latest version to my web server. When I ask people to playtest the game they usually get an old cashed version instead of the latest. Is there any way to prevent this, as clearing the browser cache every time becomes tiring and doesn't always work well.

Any way to force the browser to reload all, after an new export is uploaded?

Delete the offline.appcache and dont reupload it. That will force the user to load all the files each time.

OR add some random querystring like yourgame/index.html?v=321

Put a version number on the title screen

Delete the offline.appcache and dont reupload it. That will force the user to load all the files each time.

This solution seems to fit nicely. Thanks!