What you need

A computer with your videos, a free StashDB account, and some room for what x4u makes.

• A computer that holds your videos. Windows 10 or 11 (64-bit), a recent macOS, or 64-bit Linux. ffmpeg comes with x4u on Windows and Linux; on a Mac, install it with Homebrew (brew install ffmpeg).
• x4u itself, from Patreon.
• A free StashDB account, so x4u can name your scenes, performers and studios. x4u works without one, but your library is just file names.
• Room for what x4u makes: previews, thumbnails and every picture it shows, saved so it all works offline. A few gigabytes for a small library, tens of gigabytes for a big one.

x4u never changes, moves, renames or deletes your videos by itself. Tidying up is up to you: put what you don't want in its recycle bin, and it's deleted only when you empty the bin, after a last warning.