Fallout 76 weapon mods

Overview
Weapon mods can be distinguished into two main types, craftable and loose mods. What both types have in common is that they decrease the maximum condition of the weapon they are attached to.

Craftable
Craftable mods are always created at a weapons workbench and are directly added to the selected weapon's mod slot (the technical term being "attach point"). Note that newly created modifications will always overwrite an existing mod in the same slot, which is different from Fallout 4, where replaced mods were stored in one's inventory.

Requirements
Craftable mods may have up to three prerequisites, depending on the individual mod and the weapon it is attached to:
 * A certain amount of components - Varying amounts of components are required for the majority of craftable mods, the exception being a small number of standard mods for some weapons, which require none.
 * Knowledge of how to craft the mod - Knowledge is gained in different ways. Basic mods tend to be either known by default or become unlocked when picking up a weapon for the first time. Another common way for a majority of mods to be learned is unlocking via weapon scrapping. During the disassembling process, there is a chance ranging from high (25%) to very low (10%) to unlock a particular mod for the weapon scrapped. The last method of unlocking mods is by learning plans, which can be acquired by various means.
 * Intelligence-based perks related to crafting - The third possible requirement is different kinds and ranks of perks, which are usually required for more advanced mods. In particular, these perks are:
 * Gunsmith - For most conventional ranged firearms.
 * Science, Science Expert and Science Master - For most energy weapons.
 * Makeshift Warrior - For most melee weapons.

Loose mods
Loose mods, colloquially referred to as mod boxes, differ from craftable mods in several ways, including:
 * Requiring neither components nor perks to be attached to their associated weapon.
 * They can be scrapped for a small number of components.
 * They can be picked up and are stored in one's inventory by default. They have both a value in caps and weight.
 * Some weapon modifications can only be acquired in form of a loose mod, such as mods for the Enclave plasma gun.

Means of acquiring
Loose mods are usually tied to one or several of the six regions of Appalachia. In those regions, they may randomly be found in various locations, obtained as a reward for completing quests and events or sold by vendors. There is no guarantee to find a particular mod by any of the aforementioned methods. Known ways of acquiring a mod are listed on each individual mod page, found in the tables below.

Legend:

A weapon mod cut from the game before its initial release.

A weapon mod found in the game files, but not in the game itself.

A weapon mod removed from the game, and is now legacy.

Irregular mods
The following mods are not learnable from a plan or via weapon scrapping and therfore can't be crafted at a workbench. There are no loose mods for them found in the game, they can only be found already attached to weapon.