While Notion doesn’t confirm whether it compresses images users upload, we’ve done some research and can confirm it does not.
This is something you can test at home: Note the file size of an image and upload it to Notion, then download it and compare the file sizes. They’re the same, right? That’s because it hasn’t been compressed. Had it have been, the size of the file downloaded would be smaller than the one uploaded.
We carried out this exact test on a batch of images of varying file sizes and found that Notion returned them in the exact same condition we uploaded them in – there was no discrepancies in file size whatsoever. We even added a custom hash to the files and they weren’t stripped out or edited in transit.
This can be considered proof that notion does not compress images – for now, at least.