The short version

A proxy is, in Brolla’s own words, “a small all-keyframe copy used only for smooth preview.” Think of it as a lightweight stand-in: a smaller, easier-to-play version of a clip that exists purely so you can watch it without stutters inside Brolla.

The key reassurance is this: “Your original is never changed, and exports always use the original.” The proxy is only ever used for previewing on screen. The full-quality file you imported stays exactly as it was.

Why big or ProRes files stutter

Some files are simply hard work for a computer to play back in real time. Very large clips carry a lot of data per second, and certain professional formats like ProRes are built for editing quality rather than smooth casual playback. When Brolla can’t play one of these comfortably, you’ll see a note such as “Large file — build a preview to watch it here” or, for a tricky codec, “This codec can’t be previewed here.”

That’s not a fault — it’s just the nature of heavy footage. A proxy solves it by giving Brolla a lighter version to show you.

Why this is safe

Because a proxy is a separate little copy, building one never alters your footage. You can make proxies, delete them, and remake them as often as you like. And when it comes time to export, Brolla quietly reaches past the proxy and uses your original, so your finished result is always full quality.