Fixing “Media Error: Format(s) Not Supported or Source(s) Not Found” on Videos

If you’re seeing the error Media error: Format(s) not supported or source(s) not found when trying to load an MP4 file or Vimeo video on your WordPress site hosted on Staq, this guide will help you resolve it.

What’s Causing the Issue?

In most cases, this is not a server or cache issue — it’s related to how video files are being handled by Staq Optimizer’s Lazy Load feature within Media Optimization.

We’ve confirmed that the issue can be replicated when the video file is unintentionally lazyloaded, causing rendering problems during playback.

You can test this by appending ?no_cache to the end of the website URL. If the video loads correctly, the issue is likely related to JavaScript optimization or lazyload rendering.

Solution #1 – Exclude the Video from Lazy Loading

Inside the backend of WordPress, click Staq Hosting > Optimizer > Media.

Under the section “Exclude images & videos from lazyloading”, enter the video file name — not the full URL and not the Vimeo embed code:

Example:
If the video is hosted on Vimeo and the embedded link looks like:

https://player.vimeo.com/progressive_redirect/playback/000000/rendition/1080p/file.mp4

Then all you need to enter in the lazyload exclusion field is:

file.mp4

as per above screenshot and that’s it! You do not need to enter the full URL — Staq will automatically detect it based on the file name.

Solution #2 – Disable Staq Lazyload (Use Native WordPress Instead)

If you prefer to let WordPress handle lazyloading instead of Staq Optimizer:

1. Click Extra Options and toggle “Disable Lazyload in WordPress core” to OFF.

This will allow native WordPress lazyload to handle media, which often plays better with embedded videos and external media services like Vimeo.

Conclusion

This issue stems from frontend rendering conflicts caused by aggressive lazyload optimizations. By either excluding specific video files or switching to WordPress-native lazyloading, you can regain control over how your videos load and prevent playback issues.

Still not working? Reach out to Staq Support and we’ll help you troubleshoot further.