If you’ve stumbled across a file named in your site’s media library, server logs, or source code, you might be wondering what it is and why it has such a cryptic name.

Systems use this "source" file to create smaller, optimized versions (transcodes) for different devices and internet speeds.

Avoid using the _source.mp4 link for public-facing embeds. It is usually too large and will cause slow loading for viewers. Use the optimized/processed versions instead.