What is the stream folder in FiveM?

When the server starts a resource it scans the stream folder at the root of that resource, including its subfolders, and builds a list of the files inside. A player who joins receives that list; the files themselves are downloaded into a local cache as the game needs them and are treated as if they were part of its own archives. From then on the engine loads and unloads each asset on demand as it is needed nearby, which is the meaning of streaming in GTA V.

Subfolders are allowed and are purely for organisation: stream/mycar/mycar.yft works the same as stream/mycar.yft. Only the file name identifies the asset. According to Cfx.re's documentation, FiveM for GTAV Enhanced loads a stream_enhanced folder instead of stream when a resource has one; Alchemist vs mod converters covers that and the tool that converts Legacy assets.

Meta files are loaded through files and data_file entries in fxmanifest.lua instead.

mycars/
  fxmanifest.lua
  data/
    car1/vehicles.meta
    car2/vehicles.meta
  stream/
    car1/
      car1.yft
      car1_hi.yft
      car1.ytd
    car2/
      car2.yft
      car2_hi.yft
      car2.ytd

Because assets are identified by file name alone, names must be unique across every started resource. This single rule explains several behaviours:

• Replace vehicles: a file named after a stock asset, such as adder.yft, takes the place of the base game's file. That is how a replace mod works with no meta files.
• Conflicts: if two resources stream a file with the same name, only one of them is used, and it may not be the one you expect. Two car packs that both include the same shared texture dictionary are the usual case.
• Renaming: changing a car's spawn name means renaming its stream files as well as editing its metas.

• Oversized assets: the server warns about any streamed file that needs more than 16 MiB of memory, and such files can fail to load for players. The file is still streamed; the warning is not a block. See the "16 MB limit" guide.
• Folder named Stream or streams: only a folder called exactly stream, directly inside the resource folder, is scanned. Use lowercase, which also avoids surprises on Linux.
• New files not picked up: after adding files, run refresh and restart the resource, or restart the server. Players may need to reconnect to download them.
• Total size: players download every asset they come across, and it stays in their cache. Hundreds of unoptimized cars mean long first joins and pressure on the streaming budget.

The Resource Inspector lists the largest stream files in a resource and flags the oversized ones. When combining many cars, the Car Pack Builder removes identical duplicate assets and reports name conflicts.