File Sharing App: Intermittent 403 Errors on Thumbnail Display

Other Questions Google drive
1

Our team built a file-sharing app that’s acting up. Here’s what’s happening:

  1. Users share files, making them public but unlisted.
  2. Other users can see a list of shared files.
  3. When they try to view file info and thumbnails, we sometimes get 403 errors.

It’s weird because:

  • API calls seem fine, no visible limits hit.
  • Opening thumbnails in new tabs works.
  • All devs get the error at once, despite different IPs.
  • Single file requests can trigger it too.

We’ve ruled out:

  • Too many requests at once
  • Authorization issues

The thumbnails eventually start working again on their own. Any clue what’s causing this? We’re scratching our heads here!

2

I’ve encountered similar issues in my projects before. One thing that often gets overlooked is server-side file permissions. Even if the API calls seem fine, there might be a mismatch between the permissions set on the files and the user or process trying to access them.

In our case, it turned out that our web server was running under a different user than the one who owned the files. This caused intermittent 403 errors when the server tried to access certain files. We solved it by adjusting the file ownership and permissions.

Another potential culprit could be antivirus or security software on your server. These can sometimes interfere with file access, especially for newly uploaded or modified files. It might be worth temporarily disabling such software to see if it resolves the issue.

Lastly, check your server logs thoroughly. Often, there are subtle clues hiding in there that can point you in the right direction. Good luck troubleshooting!

3

This sounds like a tricky issue. Have you considered caching problems? Sometimes CDNs or intermediate caches can cause intermittent 403 errors if they’re not properly configured or if there’s a mismatch between cache settings and actual file permissions.

Another possibility is rate limiting at the infrastructure level. While your API might not show limits, your hosting provider or CDN could be imposing restrictions you’re unaware of.

It might be worth implementing detailed logging for these requests, including response headers. This could reveal patterns or specific error messages that aren’t visible in the browser.

Lastly, check if there’s any difference in how your app handles initial thumbnail requests versus subsequent ones. There might be a session or token issue that’s causing the first attempt to fail but allowing later ones to succeed.

4

hey there, have u checked ur web server config? sometimes weird 403s pop up cos of funky rules in nginx or apache. also, maybe look into ur CORS settings? those can be a real pain and cause random issues like this. just a thought, hope it helps!