Why mod files are so big
A single car mod for BeamNG.drive can run to a couple of gigabytes, and a Farming Simulator map further still. Set that against the base game and it looks wrong. It is not. A game ships assets that a studio has squeezed through a build pipeline for a known hardware target. A mod ships assets the way the author made them, usually at a resolution the base game never used.
Textures are almost all of it
A modern surface is not one image. It is a set: a colour map, a normal map that fakes the fine bumps, a roughness map that tells the renderer how sharp the reflections are, and often metallic and ambient occlusion maps on top of that.
The arithmetic is unkind. A 4096×4096 texture is about 16.8 million pixels. At four bytes a pixel, that is roughly 67 million bytes, or 64 MB in the units Windows shows you. The same image at 1024×1024 has one sixteenth the area: 4 MB. Four times the resolution means sixteen times the size, every time.
Stored as GPU block-compressed data it comes down, but the ratio does not change. BC7 uses one byte a pixel, so a 4K map is 16 MB and the 1K version is 1 MB. BC1 is half that again. Multiply by three maps in a set:
| One material set (colour, normal, roughness) | At 1024 | At 4096 |
|---|---|---|
| Uncompressed, four bytes a pixel | 12 MB | 192 MB |
| BC7, one byte a pixel | 3 MB | 48 MB |
Now count the sets on a car. Body paint, glass, interior trim, seats, dashboard, wheels, tyres, brakes, engine bay, underbody, lights. Ten or a dozen sets is easy to reach. Ten 4K sets is a few hundred megabytes before a single mesh or sound file is added. That is an order of magnitude, not a measurement of any particular mod.
Why the base game feels smaller
The studio knows exactly what hardware the game has to run on and what each surface is worth. A texture that covers half the screen gets 4K. A bolt head that is never seen closer than three metres might get 256. Everything goes through a build step that picks a GPU-compressed format per map type, strips channels nobody reads and packs three greyscale maps into the three channels of one image.
A mod author has no such step. The working files are made at whatever resolution looked right in the editor, and the mod ships close to that. Nothing decides that this particular wheel nut can be a quarter of the size. So the mod is not badly made. It is unoptimised in a way the shipped game never is.
Meshes, several times over
Each visible object usually exists more than once in the file. There is the full-detail mesh for when you are standing next to it, then a chain of simpler versions the engine swaps in as the object gets further away. If each level carries about half the triangles of the one above it, the whole chain costs a little under double the top level on its own.
On top of that there is collision geometry, separate from anything you see. Physics needs a shape it can test cheaply, so it gets its own much simpler mesh. Meshes are still a smaller share than textures on most mods, but a detailed body shell with its LOD chain is not nothing.
Sound
An engine cannot be one recording played faster and slower. It is sampled across the rev range in layers: on throttle and off throttle, several load points, exhaust and intake, cabin and exterior. The game blends between them as the revs move. That is dozens of short samples for one vehicle.
Audio has its own arithmetic. Mono, 16-bit, 44.1 kHz is 88,200 bytes a second, about 5 MB a minute. Stereo doubles it. Compressed formats cut that a long way down, but dozens of samples still add up, and uncompressed audio is common for the same reason big textures are.
Why the .zip barely helps
Zip compression looks for repetition and replaces it with references. Images and audio have already had their repetition removed by their own compression, so there is very little left for zip to find. The archive ends up close to the sum of its parts, and a 2 GB mod downloads as roughly 2 GB.
Why authors ship it big anyway
Downscaling would fix it: a 4K set becomes a 1K set and the mod loses most of its size. Two things stop it. A downscaled mod looks worse in screenshots, and screenshots are how people decide what to download. And it only goes one way, because once detail is thrown away it cannot be put back without redoing the work.
What this means when you download
On ModsDrop, every file has its own page at modsdrop.com/f/ plus an eight-character code, and the size is on it. Read that before you press Download.
- Downloads resume. If the connection drops on a 4 GB file, you carry on rather than start again. The signed link is valid for six hours, which is the window you have to finish or resume in. After that, open the file page and press Download for a fresh one.
- There is a speed cap, and it is deliberate. The first 25 MB come at full speed, then each stream is limited to 6 MB/s, and you can have four downloads going at once. Storage is shared between everyone using the site, so an uncapped stream is one visitor taking bandwidth from the rest. 6 MB/s is about 360 MB a minute, so a 2 GB file takes roughly six minutes and a 5 GB file roughly a quarter of an hour. That is a ceiling, not a promise: your own line decides the rest.
- Plan for several gigabytes. A handful of large mods is a bigger download than some whole games.
The download guide covers the countdown and the link itself.
Checking you have room, on Windows
Open File Explorer and click This PC. Each drive shows free space under its name. Right-click a drive and choose Properties for the detail. Settings, then System, then Storage shows the same figure with a breakdown.
Check the drive the game lives on, not just C:. If the game is on a second drive and your downloads folder is on C:, both need room.
Leave more than the archive size. While an archive is being extracted, or while a game unpacks a copy of its own, both copies exist at once. Plan for roughly twice the download, then delete the archive once the mod works.
“Unexpected end of archive”
A half-downloaded archive looks completely normal in Explorer. It has a name, an icon and a size. What it lacks is the end of the file, and a zip keeps its index of contents there. The archive tool goes looking for that index, finds nothing, and reports that the archive is corrupt or ends unexpectedly.
There is nothing to repair. The bytes were never received. Compare the size on your disk with the size on the file page, and if it is short, download it again. Because transfers resume, that usually means finishing the download rather than repeating it.
Prune the mods folder now and then
Mod folders only grow. Old versions stay behind after an author updates, mods you tried once sit there for months, and a game that keeps an unpacked cache holds a second copy. A few gigabytes accumulates without you noticing.
Sort the folder by size, work from the top, and remove what you no longer load. Keep a copy elsewhere of anything you might want again, because a mod that disappears from the internet does not come back.