RedM files
Drop RDR2 and RedM files, or a whole resource folder. Each file is read from its bytes: a texture dictionary shows its textures, a model its LODs and collision, a map file its entities, a manifest whether RedM will start it. Then it points at the RedM tool that opens it.
Everything stays in this browser. Nothing is uploaded.
Where do the files go?
Into this browser's own storage on this machine, and nowhere else. No account, no server, no upload. The RedM workspace is kept apart from the FiveM one. Clearing site data for fivemad.com, or opening the page in a private window, means an empty workspace.
How is a file identified?
By its first bytes, then by its name. An RDR2 resource says RSC8 and carries a resource id, and the id says whether it is a texture dictionary, a model, a fragment, a map file or a clip dictionary. If the name and the bytes disagree, the page says so instead of trusting the name.
What it will not do
It does not read your disk or your RDR2 install, and it cannot open an encrypted or Oodle compressed file. The game's own archives (RPF8) and the files inside them are encrypted with keys a browser does not have, and the game packs its resources with Oodle. Export what you need with CodeX on your own machine, unencrypted and with no compression or Deflate, and drop that.
Versions and backups
Adding a file whose name is already in the folder makes a new version instead of overwriting. The first copy and the nine newest after it are kept, and restoring an older one only changes which is current.