These are all of the Armor, Weapon, and Ship mods in Destiny 2. If we get other types of mods, I’ll add them in.

A special thank you to Datto, FalloutPlays and Mercules for laying some of the groundwork that went into this.

Notes for Using This Guide

• Ctrl-F is your friend. Want to find all of the Helmet Mods, or all of the Reload Mods, or all of the [insert word here] Mods? Ctrl-F, Guardian.
• I have done my best to ensure total accuracy with all numbers, referencing the work of others where possible and confirming their work with my own testing, which is ongoing. Where possible, I measure mods that affect the speed of things by counting frames. Ultimately, I had to make some estimations due to rounding and it’s always possible I miscounted frames. Please feel free to double check me and tell me if I screwed up.
• I am rounding to the nearest second, rather than providing you fractional times. There's a limited benefit to being more accurate, and I can't confirm every number down any further than that anyway.

Armor Mods

I’m not the first person to list out all of the armor mods, but I’m hoping that some solid numbers and the presentation in a searchable list instead of a spreadsheet will add some utility I haven’t seen elsewhere. See below for some notes and explanations.

Notes on Cooldowns:

Important: Class Ability refers to Dodge, Rift, and Barrier. Those mods do NOT affect Grenade or Melee cooldowns. I did test for that.

One interesting thing I found is that all cooldown mods have the same effect. The "diminishing returns" people have been talking about are in fact a function of these mods reducing cooldowns by a percentage rather than a fixed number of seconds. These mods stack, so having two Paragon Mods reduces your Class Ability cooldown by 33.334%, and 3 Mods by 50%. This holds true across all classes and abilities. I originally timed these directly and compared with Datto's research to corroborate. Since then, Bungie has provided exact figures (which changed from the time of original publication.

Thanks to /u/tortoisemeyer for some math notes.

FYI on Cooldowns
Grenade Cooldowns are ~83 seconds. Titan and Warlock Melee Cooldowns are ~83 seconds, except for the Stormcaller Melee which has a ~96 second Cooldown. Hunter Melee Cooldowns are also ~96 seconds. As for Class Abilities, Hunter Dodge Cooldown is ~25 seconds, Titan Wall Cooldown is ~38 seconds, and Warlock Rift Cooldown is ~83 seconds.

Cooldown Time Math
With 1 Mod = Seconds x .83
With 2 Mods = Seconds x .67
With 3 Mods = Seconds x .50

Notes on Handling/Reload Speed: 

To check the effects of the Reload Speed and Handling mods, I recorded myself reloading and, erm, handling (that is, equipping, stowing, and aiming down sights/zooming back out) weapons with and without those perks. I used weapons with both high and low stats to see if the effects were a set number of frames or a percentage. They were clearly a percentage as the number of frames varied widely. I need to do some more testing on Kinetic Munition Loader as I have to rely on third parties (it hasn’t dropped for me somehow), but I thought it was interesting it gave a different bonus than the Power Munition Loader.

Handling was tough to work out, because ADS, Equip, and Stow are so fast that the real percentages were all over the place, but they average out to ~15%. Allowing for rounding, multiplying by .85 with a mod on gave me all of the right numbers, so I’m going with that until I find evidence otherwise.

There does seem to be a cap on the effects of Handling and Reload Speed, and there is likely a cap on other stats. I will try to test more when I can, but I noticed guns with very high stats (looking at you, Hard Light and Wardcliff Coil) did not get the full benefit that guns with lower stats did. Bear this in mind.

Notes on Counterbalance/Recoil Direction: 

To calculate the effects of Stability mods, I shot at walls without attempting to control the recoil, and measured the horizontal and vertical height of the impacts using image editing software. Counterbalance Mods definitely have an effect on Recoil Direction and seem to increase that stat directly, as you can see in this gallery of shots from MIDA Multi/Mini and Origin Story. Mercules got similar results with Lincoln Green, and I’ve had a number of other similar test results.

In these shots, you can see clearly that the recoil does change, but there is always some randomness to it. For now, I’m not comfortable putting an exact number on this effect, but it is definitely converting horizontal recoil to vertical recoil, and will therefore be helpful when you are having trouble staying on target with a gun.

The effect is more obvious and pronounced on weapons with less vertical Recoil Direction, and less so on weapons that already have a highly vertical Recoil Direction. The type of weapon and your in-game rate of fire will also affect whether or not you feel the benefits of these perks. Obviously, the faster you shoot, the more likely you are to notice the difference.

Note: The Precision Frame Intrinsic Perk seems to apply this same effect in a manner which does not stack, rendering Counterbalance Mods effectively redundant on Precision Weapons.

If you don’t know, a RD stat at 90-100 indicates generally vertical recoil, RD of 70-80 is generally vertical but favors bouncing either left or right, and RD below 60 is fairly horizontal, either favoring one side or bouncing back and forth a lot. The exact pattern is somewhat random and varies by gun.

Weapon Mods

These are included for completeness’ sake, and in case we get more in the future I can come back and add them in. Hopefully they eventually do something more interesting. ¯\_(ツ)_/¯

All of these Weapon Mods have Legendary versions that grant +5 Power. The Legendary version of the Kinetic Damage Mod is the Weapon Attack Mod, which is why I listed both names. The others are named the same.

Masterwork Perks (AKA Masterperks)

Masterworks were introduced with Curse of Osiris, and add an additional possible perk node to Legendary Weapons. Weapons can drop as Masterworks with a random Masterperk selected, or you can dismantle Masterworks to get Masterwork Cores to upgrade any Legendary Weapon (Total Cost 10 Core and 25 Legendary Shards). Following are all possible Masterwork Perks.

*A Final Note: As this may be unclear, the Magazine bonus gives 10% to Magazine size and Ammo Capacity (reserve ammo). It does round down on the examples I've seen, since you can't fire half a bullet, but let me know if you find one that seems to round up.

Ship Transmat Effects

Obviously these are all cosmetic, but I was on a roll and there are probably some collectors needing a list, right?

Okay, that's all we've got for now. Please feel free to share this guide around, and reference it in your own work. All we ask is a shout-out and a link back here. Enjoy!

-kyt_kutcha

EDIT: Corrected some numbers in the cooldown explanation. I had originally estimated 8%, but recounting frames found it was actually closer to 9%. Then edited again to fix a formatting issue that the first edit somehow triggered. :-/
EDIT: Corrected notes and math regarding how Cooldown Mods stack. Also added notes to clarify that Stat Mods stack as well.

EDIT: Updated for Curse of Osiris. Added new locations to several Armor Mods, added Masterwork Weapon Perks since they are similar in function, and also added a bunch of Transmat Effects.

EDIT: Updated for the March Update, changing Grenade/Melee/Ability Recharge Mods and related notes, correcting Grenade recharge times, and removing the Mod Tier list as it was far out of date and not adding value.