PDF Compression

[brigitte-at-seesaw]

brigitte-at-seesaw last edited by

This is not actually a problem with Opera, but rather a request for clarification on how the browser works. I work for Seesaw, answering emails to help solve customer problems. We've recently seen an uptick in tickets where PDFs show up blank when uploaded to a Seesaw post. To quickly explain that, Seesaw users can upload PDFs to a post. This converts the PDF into movable, resizable images across multiple pages. The issue being reported will make a 5 page PDF display as 5 seemingly blank pages on Seesaw; these blank images can still be moved and resized. It does not happen with all PDFs, so normally we would assume there is a corrupt asset in the PDF itself. However, customers have reported that when they tested other browsers, Opera is the only browser where uploading PDFs works properly. Our Research/Testing squad has done a lot of research as to why it might not be working in other browsers, but we are wondering why Opera works. We know that Opera has built-in compression technology. Could this be compressing/repackaging the PDFs, causing Opera users not to run into the same issue?

[leocg]

leocg Moderator Volunteer @brigitte-at-seesaw last edited by

@brigitte-at-seesaw Nope, Opera for desktops doesn't compress data as far as I know.

[burnout426]

burnout426 Volunteer last edited by burnout426

Have you been able to reproduce the problem yourself? As in, do you have an example PDF that reproduces the problem in other browsers?

If so, try uploading the PDF in Opera GX, regular Opera, Opera Beta, and Opera Developer to see if any of them reproduce the problem. If you goto the URL opera://about, you can take note of the Chromium version in the user agent string. Perhaps the issue is limited to a certain major version of Chromium. Different Operas use different major versions of Chromium. I would also compare with Chrome, Brave, Chromium, Edge, and Vivaldi. And, don't just test with stable versions, but beta and dev versions too.

Do you have data on the user agent string for users that have reported this problem? They all Windows users too? Or, are some on Chromebooks?

Have any Firefox user reported this problem or just users of Chromium-based browsers besides Opera?

If you have a test pdf that triggers the problem in other browsers bu not Opera, in Opera, goto the URL opera://flags/#freeze-user-agent, enable the flag, restart opera and see if Opera then triggers the issue too. If so, it's like a browser sniffing issue with the Seesaw upload code.

In short though, Opera shouldn't be any different than any other Chromium-based browser besides its user agent string.

Just for extra testing though, in Opera, goto the URL opera://settings/userInterface, disable "Show popup with clipboard and recent downloads when uploading files", restart Opera and test all Opera's again. It's very, very, very unlikely. But, maybe that feature (enabled by default) somehow works around the problem you get in other Chromium-based browsers.

[brigitte-at-seesaw]

brigitte-at-seesaw @burnout426 last edited by

@burnout426 Thank you so much for your insight! We did not think about other browsers having different Chromium versions. It turns out the issue only occurs for newer browser versions: Chromium version 92 and newer, and Firefox 90. Basic Opera and Opera GX apparently use Chromium 91. The PDFs upload correctly within Safari, but that hasn't been updated since 2015, so that makes sense. We're still researching why it only happens for some PDFs rather than any PDF, but it's good to know it's most likely related to recent browser updates.