I allow multiple form submits on my sites. What I don't do is allow the same form to be submitted twice if the checksum of values it is submitting is the same a

I allow multiple form submits on my sites. What I don't do is allow the same form to be submitted twice if the checksum of values it is submitting is the same as a prior submit. This allows for the best balance between preventing double-submission errors, and a good user experience if a user has made an error. I still de-dupe check on the server too (in case JS is disabled), and in a distributed environment the server submissoin de-dupe check isn't guaranteed (what if two submissions went to different servers?). Perhaps if anything should be added to browsers it's simply a checksum of all of the values to submitted and an option to prevent submission if a prior checksum has been submitted. But even then... this is trivial to do in JS. The above only applies to POST, for GET I don't care... it's cached, and perhaps the second request is the because the first one stalled (bad mobile network, etc).