App Store screenshots return "File not found" through usercontent.apps.nextcloud.com

[JoaoMSacramento]

Description

Screenshots for my newly published app, Markdown Wiki (markdown_wiki), are not displayed on the Nextcloud App Store.

The App Store detects the screenshots and displays the screenshot carousel and navigation arrows, but the images themselves are blank.

The screenshot URLs are public HTTPS URLs hosted on raw.githubusercontent.com and work correctly when accessed directly.

Example

Screenshot URL:

https://raw.githubusercontent.com/JoaoMSacramento/markdown-wiki/main/screenshots/markdown-wiki-main.png

Direct request works correctly:

HTTP 200
Content-Type: image/png
Content-Length: 259713

However, when the same URL is requested through usercontent.apps.nextcloud.com, the response is:

HTTP 200
Content-Type: application/octet-stream
Content-Length: 14

File not found

Tests performed

I tested:

• The screenshot from the main branch
• The screenshot from the v0.1.1 tag
• The same image copied to appinfo/screenshot.png

All of them are accessible directly from raw.githubusercontent.com, but all return File not found through usercontent.apps.nextcloud.com.

As a control test, I tested the screenshot used by the Memories app:

https://raw.githubusercontent.com/pulsejet/memories/master/appinfo/screenshot.jpg

The Memories screenshot works correctly through the same usercontent.apps.nextcloud.com service.

This suggests that usercontent.apps.nextcloud.com is reachable and can retrieve images from raw.githubusercontent.com, but for some reason it cannot retrieve the Markdown Wiki screenshots.

App information

• App ID: markdown_wiki
• Version: 0.1.1
• Repository: https://github.com/JoaoMSacramento/markdown-wiki
• App Store page: https://apps.nextcloud.com/apps/markdown_wiki
• Supported Nextcloud versions: 31–34

[edward-ly]

Thanks for reporting! My guess for what happened was that there was some kind of failure when usercontent.apps.nextcloud.com tried to download the screenshot, but the failure wasn't recorded correctly. We'll see if we can clean this up on our end.

[aktasfatih]

Hi, this happens for Kanso as well https://github.com/aktasfatih/kanso. Thanks.

[martin-rueegg]

Found the cause: since the app store started serving screenshot URLs already in proxy form (nextcloud/appstore@fd69d12680), sync.php encodes the proxy URL a second time and fetches the proxy itself, so screenshots published since then are never fetched. All 70 "File not found" URLs in today's apps.json belong to the 18 apps whose newest release is 2026-09-20 or later, whatever host they are on. Fix and measurements in #31.