Bethesda mod archives
The Gamebyro engine can load files from specialised archives into the game on startup. This allows DLCs and mods to package all their files together without worrying about them being accidentally overwritten and further simplifies the modding process by minimising the number of files. These archives can be either BSA (Oblivion, Fallout 3, Fallout New Vegas and Skyrim) or BA2 (Fallout 4 and Fallout 76) format files. Extracting or modifying archives should be considered an advanced modding technique and in most cases is unnecessary to allow the game to function correctly.
Mod archive compatibility
The BSA and BA2 archives are not automatically compatible with all games. Even among the variations of the same file type, they can cause unwanted side effects such as preventing the game from starting up. The table below lists the types of BSA and BA2 and how they behave with each Gamebyro title.
| Game | BSA v103 | BSA v104 | BSA v105 | BA2 v1 |
|---|---|---|---|---|
| Oblivion | Compatible | Ignored | Ignored | Ignored |
| Fallout 3 | Untested | Compatible | Untested | Ignored |
| Fallout New Vegas | Untested | Compatible | Untested | Ignored |
| Skyrim (2011) | Limited Support | Compatible | Incompatible | Ignored |
| Skyrim Special Edition | Incompatible | Incompatible | Compatible | Ignored |
| Fallout 4 | Ignored | Ignored | Ignored | Compatible |
| Skyrim VR | Untested | Ignored | ||
| Fallout 4 VR | Ignored | Ignored | Ignored | Compatible |
| Fallout 76 | Ignored | Ignored | Ignored | Compatible |
