Mods

Modifications (Mods) are cards that can be equipped to warframes, weapons, and sentinels to enhance damage, power, survivability, speed, precepts, and utility. Mods can grant Passive Powers, Active Powers, Sentinel Precepts, and Utilities. Mods can be changed between items.

For a visual guide to mods, see this video

Obtaining mods
Mods are collected in a few ways:
 * Purchasing frames, weapons, and sentinels with platinum will give a few mods. A Warframe comes with its 4 Power Mods. A Sentinel comes with 2 Precepts.
 * Making frames via blueprint gives you all 4 power mods.
 * Dispatching enemies. It has now been confirmed that the higher level the enemy, the rarer the mod that they can drop. Though, higher level enemies do not have a higher drop rate. Mods are always dropped as level 0 mods. The type of mod will appear in the right center of the screen when a mod is picked up. Sometimes, they will be Fusion Cores (see fusion energy, below) instead of regular Mods.
 * Ever since the Update 7.7, Common Mods will now drop at a high percentile, Uncommon mods with drop at a lower percentile and Rare Mods will drop at an extremely low percentile. However, the chances of obtaining Rare Mods are increased in higher levels.
 * Raid/Spy/Capture missions offer a mod upon completion normally being Stamina Regen, Stamina Max, Vitality, Sprint Speed or an Ammo/Magazine/Reload mod.
 * Every 5 waves of defense missions will offer you a reward if you decide to exit. The rewards are random each time but tend to offer rarer mods the higher the wave you get to. With the new Update 7.7, Defense mission rewards have become the main source of Rare Mods.
 * Purchasing Mod Packs from the market.
 * Each faction has a higher chance to drop certain mods, while having a small chance to drop other mods as well. The following is what each faction drops most often.
 * Infested: Power Abilities, All types of Freeze damage.
 * Corpus: Fire/Electricity/Armor Pen. Mods, Power Max, Power Efficiency, Power Range, Melee Charge Speed, Loot Radar and Enemy Radar, Puncture Mods. (Tactic Polarity: )
 * Grineer: Critical Hit Chance, Critical Hit Damage, Multishot, Basic Damage Mods, Power Duration, Power Strength. (Attack Polarity: )
 * Universal: Fusion Cores, Sentinel Mods, and Stun. However, you are more likely to gain Fusion Cores on lower level worlds such as Mercury, Saturn, and Venus.

Attributes
Mods have 6 attributes: (place on card)
 * Type: What the mod can be attached to. (Top left of description)
 * Rarity: How often a mod is dropped. (Top right of description and color of border)
 * Power cost: How much power a mod consumes from equipment. (Center right)
 * Polarity: Adjusts power cost of mods. (Top right of card)
 * Level: Mod strength. (Border, Center Left and with Rarity)

Type
Mods can only be attached to their indicated type of item. They may be generally applicable to weapons, warframes, or sentinels (i.e. “Warframe Mod”) or specific to their respective class (i.e. “Trinity Mod”). The type is listed in the top left of the description of the mod.

Mod Rarity
Mods vary in rarity as indicated by the border color and denoted in the description. Obtaining rarer mods from enemies requires fighting higher level enemies. (confirmed, higher level enemies have a higher chance to drop rare mods)
 * Bronze - Common
 * Silver - Uncommon
 * Gold - Rare

Mod Power Cost
Warframes, sentinels, and weapons have “Mod Energy.” This reflects the items ability to maintain mods while in use. Warframes and sentinels have 10 slots for mods. Weapons and sentinel weapons have 8 slots. Without an Orokin reactor or catalyst, they can all handle 1 energy worth of mods per level (with a maximum of 30 energy at level 30). Supercharged items (with reactor/catalyst) can handle 2 energy per level (with a maximum 60 energy at level 30).

Polarity
Most equipment slots generally accept any mod. However, some slots are “polarized.” Each type of Polarization has a unique associated symbol.

Mod Rank
Mods have levels ranging from 0 to as high as 10 (typically 3-5; note that this means each mod has its max level +1 in total level ups). When the level of a mod is greater than zero, it is indicated by notches in the border centered vertically on the left side of the card. Higher level mods require more mod energy.

Installing Mods
To install mods on an item, drag a mod from the collection and drop it on a Mod slot. If the Mod’s drain is less or equal to the item’s remaining Mod Energy it will install and Mod Energy will be deducted. Drain can be modified by the slot type: The item now has the benefits of the Mod.
 * Matching polarity reduces drain: Slash Dash costs 2, but dropped into Power polarized slot costs only 1. (Cost is halved for matching)
 * Conflicting polarity increases drain by a third, rounded down, with a minimum of one added: mod levels 1-5 add 1, mods 6-8 add 2 -- mods 9-11 add 3 and so on.

Bonus Stacking
To prevent exponential bonus stacking, players can't put duplicate mods in a single piece of equipment. For example, a given pistol can only have one Hornet Strike mod in it at a time.

For mods increasing shield, health or power, bonuses are calculated from the warframe's base value. This prevents exponential increases with the passive leveling bonuses introduced in Update 7.6.

Mods increasing damage or adding special damage types don't conflict with each other. Given enough mod capacity, a single weapon could have mods increasing damage and adding fire, freeze, electrical and armor piercing damage at the same time, and they would all take effect at the same time when using that weapon.

Fusion
Mods can have their overall power increased by the process called Fusion. This takes mods or Fusion Cores and combines them together to increase the overall power of a Mod.

Mod List
Warframe Mods|Warframe Rifle Mods|Rifle Shotgun Mods|Shotgun Pistol Mods|Pistol Melee Mods|Melee Sentinel Mods|Sentinel

Bugs

 * When fusing cores or other mods, selecting and deselecting mods may result in less upgrade points (visually) on the bar.
 * After selecting various rare level 10 cores to fuse, adding uncommon or common cores/mods may result in a decrease in the total upgrade points, lowering the final level even.