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What are BSA, BSL and SEQ files


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Hi Everyone


Just few questions :


What's a BSA file, what it can contains ? (yes, i want to compact scripts, meshes and textures of my mod).


For example, when i tried to made a Bsa file for my mod (esp : 500 ko), its' made a 25000 ko .bsa, and a 5ko .bsl.


How to made a SEQ file ? What's this file ?


What the way of work of the experimented modders in loverlabs community ?


Thanks in advance

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Just a quick rundown:


BSA files are archives of loose files. The game can pull pretty much any kind of resource file (model, texture, sound, behavior, animation) from a BSA. The only exception I know about is Bink video like the intro movie. Oh and of course you cannot store your mod itself (the ESP file) inside a BSA.


The BSA file format is designed for fast access and not compression, even though BSA does actually support some weak compression too.




BSL files are just for housekeeping. They are not used by the game itself, only by the Archive.EXE program that creates your BSA files.

All file paths inside a BSA are relative to the games root directory. The BSA does not store information where the file actually came from on your computer because that doesn't matter to the game. However, this matters very much to Archive.EXE if you want to rebuild your BSA because you changed some source files.

The BSL file simply contains a table that stores the absolute file path for each file in the BSA. It will make your life as a modder easier but you do NOT need to distribute this file to users. The game doesn't use it and it is virtually useless for other modders.




SEQ files are needed since the 1.6 patch. The SEQ file contains information about "Start Game Enabled" quests.

If your mod contains new quests that must be running from the very get-go, you need to create a SEQ file telling the game about it, otherwise the quest might not run, fail to run scripts, fail to enable dialog or mess up in many other ways. Thanks Obama ... I mean Bethesda.


You create the SEQ file by running the creation kit with the -GenerateSEQ:mymod.esp flag. Replace "mymod.esp" with the name of the mod file you are working on. The creation kit program will start, do some stuff and close. After that you will find a new mymod.SEQ file in its directory. Move it to ./data/SEQ and you're golden.




I hope this helps. Have a nice day and good luck.

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