It's 2022 and Google how has a "Recover Storage" option now which will compress (and subsequently remove from quota) all the original-quality photos and videos which count towards quota.
Sadly they still lack the ability to tell you WHICH ones are taking quota. The only possible explanation is that by making life difficult enough, Google can push people to give in and pay for cloud storage.
My Pixel 2XL's free original-quality uploads ended on January 16, 2021.
In my case I wanted to run "Recover Storage" but first I wanted to download the uncompressed versions to my PC. I don't want to download my ENTIRE account, as that's rather large and the older photos are still being kept in original quality anyway. So should I just select everything from 2021-01-16 to today? Well not quite, since I believe it's the upload date and not the capture date that determines storage rules.
So what I did was:
- Select everything from a date safely before that date (say, 2020-12-16, assuming I didn't do any backups that entire month); download all of those to my PC.
- Do the "Recover Storage"
- Go back to photos around that time and note the new sizes of the photos compared to the backup I just downloaded.
- Presumably, photos taken on 2020-12-16 were mostly likely uploaded before 2021-01-16 and therefore should be unaffected by the Recover Storage operation. Thus, the file sizes should be the same as the backup.
- Photos taken on 2021-01-17 would definitely be part of the compression; the new size should now be significantly less than the one I backed up.
- By finding the boundary between these two cases I can now identify exactly which of my photos have the "free original quality" privilege, and which ones don't. For the former, I can subsequently delete the redundant backups from my PC if I wish.
Going forward, my phone's backup setting will be set to "Storage Saver" to allow at least a compressed version to be automatically backed up. But I also have "Smart Storage" disabled; that way I can first copy all future original-quality images directly from phone to PC before manually freeing up space on my phone.