no-hats-bgum

if you're looking for a version compatible with Loyalists' Touhou playermodels, you can find one here.

Links to similar mods:

https://www.teamfortress.tv/56398/no-hats-mod-headsfeet-2020-edition (The original mod kept updated alongside a headsfeet variant.)
https://github.com/JarateKing/CleanTF2plus (This is a batch script that includes a nohats options.)
https://github.com/jeebsAU/No-Hats-Mod (The mod here was at first based on his mod, which is outdated now.)
No Stattracks/Action Items/Random Misc. Stuff (There you can find even more mods to remove models from the game. needs to be preloaded, read the notes below)

This is a pack of mods whose purpose is to remove some visual aspects from Team Fortress 2 (cosmetics, skins, unusuals, etc).

Note: apart from no_hats_bgum.vpk, all the mods are dormant. This means I won't add new mods or work on the existing ones. Occasional bug fixes may be released, but this is without any guarantees.
Note: Multiple versions of the so-called "no-hats-mod" exist, some people seem to forget that this isn't the only one in existence. The version provided here makes the default headgears reappear, if you want a version which only removes the hats, you can find an up to date version here or generate one yourself here. (You can even make one with nhcustom2 if you're crazy enough.)
Note: Some mods here require the models to be preloaded to work. For them, you have to use Pilso's Preloader map and settings (it even allows for custom model preloading through Vscript). It most likely won't work if you use another preload map (unless you know what you're doing).

A side by side view of no-hats-bgum ON or OFF.

Primary mod - no_hats_bgum.vpk

This is the main mod of the pack. It prevents the game from loading cosmetics and also makes the default headgear reappear, should it be removed by the cosmetic the player is wearing. (E.g. no more soldiers jumping around without helmet, safety first amarite?). The nice thing is that it works on Valve servers.

Concerning performance...

You can get a small boost in performance with this mod, but it's so insignificant (7 fps on my end) that you really shouldn't bother.
Also: I've seen a Youtube video where this mod seems to hinder performance (I'm not sure, I don't speak his language). So make your own tests.

Secondary mods

If not specified, the mod works on Valve servers.

no_bugged_misc.vpk: The main mod lets some pyro masks appear as the method to replace them doesn't work and leaves them headless. For visibility reasons they are still shown, but you can use this mod to make them invisible. Please note that this isn't working every time for some cosmetics, for some unknown reason.
no_hats_creatorstf.vpk: This mod was for people playing on the creators.tf servers, and replaces the custom cosmetics they added. When the servers shut down, this mod was a bit out of date.
no_unusuals.vpk: This files removes unusuals. Sadly, it doesn't work on Valve servers. also, if TF2 receives a new update, which adds new particles effects besides unusuals, you should remove this mod and wait for a new version to come out.
no_christmas_lights.vpk: This mod removes christmas lights from festivized weapons. Not to confuse with the limited festive weapons, not affected by this mod. Preloading required.
no_skins.vpk: This mod removes the majority of the weapon skins and warpaints. This mod doesnt work on valve servers and you need to move all your skins/warpaints at the END of your inventory, otherwise your weapons will load indefinitely. You have been informed.
no_botkillers.vpk: This removes robot heads from weapons. Preloading required.
no_zombie_skins.vpk: This one replaces Voodoo-cursed Souls skins with the default player model. This doesn't work on Valve servers. It was contributed by gabrielwoj.
no_action_items.vpk: This removes action items (powerup canteens, spellbooks, etc).

Contributing

If you ever come across a bug, you can send me an e-mail (present in this website's about page). PLEASE read the bug list and the FAQ first.
~~https://git.pevhs.ch/no-hats-bgum.git~~ (Outdated. superseded by nhm_factory written below)
https://git.pevhs.ch/no_botkillers.git
https://git.pevhs.ch/no_christmas_lights.git

Modify

Use nhcustom2. Please note that even with this tool, there are some limitations.

If you insist on doing it the manual way, you can watch these two videos to know how to do it:
Windows
Linux
But please consider using nhcustom2. It'll save you a ton of time.

More customization

If you're using Linux and you're not afraid of C and shell scripts, you can clone the repositories I use to generate no-hats-bgum:
https://git.pevhs.ch/nhschema.git
https://git.pevhs.ch/nhupdater2.git
https://git.pevhs.ch/nhm_factory.git
Here you will find what you need if you want to create, for example, a version of the mod which replaces hats with custom bodygroups like what is done with no_hats_thf.
No support given. Use your brain.

Closing thoughts

Here's a post from an anon I liked. Not specific to this mod, but it highlights well that not being able to see hats is most of the time a non-issue.