How to avoid duplicates while crossposting?

So we all know subs have strict rules.
How to see if I am crossposting gif thats already posted?
It was possible to see before in the url of redgif, just instead comments switch to duplicates and you would see places that gif was posted.
But now that option is not working. So any suggestion to see if I m posting fresh or reposted gif? Thanks

I'm also interested if anyone has a method to check for GIFs and videos. I check pictures with Google reverse image search and that's worked great so far.