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FO4 mod count cap?


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I have read in the past months posts explaining that the 256 esp/esm cap for Skyrim is because it is a 32 bit game and with FO4 the cap will be way bigger. 

However it seems this is not the case. Or is it?

Would someone please explain this? Thanks!

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Guest MonsterFish

32 bit is an incredibly large number. 32 bit would be 2,147,483,647. 255 is 8 bit and is most likely used because it's the largest exponent of 2 (2 bit, 4 bit, 8 bit, 16 bit... and so on) that doesn't break a hexadecimal value with 2 characters.

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I may be wrong but I don't think the limit has anything to do with Skyrim being a 32 bit application. They most likely just decided some time ago to assign a two digit hexadecimal value to plugins. As such, they have a range of 0-FF. It's probably hard coded and Fallout 4 most likely has the same limitation. 

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Skyrim run time IDs are done this way:


8 bytes for the actual object id. Gives 8^3=2^24=more than 16 millions possible unique identifiers for objects.

And Skyrim was a 32bits application. This gave another 8bits to give an unique id during the run time to different objects that had the same internal ID but were added by different mods.


Now Skyrim for many versions had the 32 bits as SIGNED integer, so it was problematic to use the very first bit. And the mod limit was 128 (and the game uses an id, all DLCs uses one, and 255 was always for dynamic objects.)


Sadly Fallout4 uses exactly the same way to identify objects and mods.

So the limit will be probably a little bit less than 255.


How to check? Open the CK, create a mod, create one object. Find this object using the text search, and you will find 8 hexadecimals digit identifying the object. So total of 32bits also here.


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It has to do with 32 bit used for IDs. Measing 4 byte. A byte has a value between 0 (00) and 255 (FF).

The first byte is for the load order the ESM/ESP has.


For more: http://www.uesp.net/wiki/Skyrim:Form_ID


AFAIK they haven't changed this in FO4, limiting us to 255 esp/esp files. FF is used by the game, see wiki link.

And why would they? As MonsterFish said, you can have 2,147,483,647 objects if all ID's are used. Less because you shouldn't edit the Vanilla Files.

Merge smaller mods and you use the available IDs efficiently.

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I see this topic reserge on almost everyday.


Its like people expect to be able to actually find and use 255 ESP files.


Now I've had a whole lot of different mods installed before on different games but a whole lot of them did not include plugs aka ESP, ESM files.


There is also the fact that merging files is possible and I've done that to stay well below limits.


Now here's the thing.

The guys that make it to 255 that bother to complain most likely will have already introduced complications into their game because of their modding or their mod choices.

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I think it's a valid question, my skyrim is about 255 mods with merged follower, merged armor and weapon. 


it's very time consuming to merge, and something do not merge easly. 


I had to make very hard choice as what to use mainly gameplay esp. and with the full suite of sexlab esp.. almost 20 esp.


if I count all the single mods without merging them I bet I'm over 400 (including  merged textures and script)


Right  now in FO4 there is enought mods to go up to 255 easly without merging... and merging isn't realy as easy as in skyrim...


My fallout 4 as already 132 esp. some mods add 10 esp each.


it is a sad new that I would have to do the same "work" on fo4.

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And yes, the additional 300-ish esps are all merged into 1, and yes it all works perfectly fine, without any issues, because I merged them by hand, one by one and manually resolved all potential issues. And no, I wouldn't recommend my method to anyone, because it requires quite a bit of time and effort and quite a bit of understanding the stuffs inside the esp.

Oh, and yes, I consider this a small loadorder...I had Skyrim instances with 800-1000ish mods. Not there yet with fo4, but it's just a matter of time. ^^

As I use to say...as long as you got more than 15fps, there's still room for one more mod ;P

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