Buff

Most often, a buff refers to a temporary beneficial spell or effect placed on a player. Buffs can range in effect from simple personal shields to buffs which augment almost every category of stats a given player may have for their race or class.

Buffs can be of two types: those that expire over time (simple buff like Arcane Brilliance) and those that are dependent of the environment around you (like the AoE effect given by totems).

You can dismiss an active buff that expires over time by right-clicking on its icon.

Most buffs do not stack with other similar buffs. One prominent exception is heal over time spells, heal over time spells from multiple characters and different heal over time spells from the same character (such as a druid's Regrowth and Rejuvenation) will stack with each other.

Buff can also be used as a verb, i.e. "to buff" means to apply buffs.

Buff is also used to represent a change to a class or ability that makes it more effective or useful. It is the opposite of a nerf.

By class
Death Knight:
 * Abomination's Might - attack power
 * Horn of Winter - agility and strength
 * Improved Icy Talons - increased melee and ranged attack speed
 * Unholy Frenzy - increased melee and ranged haste at the cost of health

Druid:
 * Leader of the Pack - Increased critical strike chance
 * Mark of the Wild - all attributes and resistances
 * Moonkin Form - increased spell haste
 * Thorns - reflective damage for target
 * Innervate - short term mana regeneration for target

Hunter:
 * Aspect of the Pack - run speed
 * Aspect of the Wild - nature resistance
 * Ferocious Inspiration - Increased damage dealt
 * Hunting Party - increased melee and ranged attack speed
 * Trueshot Aura - attack power

Mage:
 * Arcane Brilliance - mana pool and spell power
 * Arcane Tactics - Increased damage dealt
 * Focus Magic - increased critical strike chance for target (Arcane talent)
 * Time Warp - spell, ranged and melee haste

Paladin:


 * Auras - Auras affect the Paladin's party/raid
 * Devotion Aura - increased armor
 * Retribution Aura - reflective damage
 * Concentration Aura - reduced loss of casting/channeling time from damage
 * Resistance Aura - Fire, Frost and Shadow resistance
 * Crusader Aura - increased mount speed
 * Blessings - Blessings affect a target and it's party/raid members
 * Blessing of Might - increased attack power and mana regeneration
 * Blessing of Kings - all attributes and resistances
 * Hands - Hands are short term buffs, affect single targets
 * Hand of Protection - protection from physical attacks
 * Hand of Salvation - threat reduced over time
 * Hand of Freedom - immunity from movement impairing effects
 * Hand of Sacrifice - transfer of damage to the caster
 * Other
 * Beacon of Light - Direct heals from the casting Paladin also heal the Beacon for 50% of the healed amount if the target is within 60 yards. Not affected by LoS.
 * Communion - Increased Damage dealt while any Aura is active.

Priest:
 * Power Word: Fortitude - stamina for target/target's party
 * Power Infusion - short term increase in spell haste and reduction in mana cost of spells for the target
 * Shadowform - increased spell haste
 * Shadow Protection - shadow resistance for target/target's party
 * Fear Ward - Causes the next fear effect cast on the target to have no effect.

Rogue:
 * Honor Among Thieves - Increased critical strike chance
 * Master Poisoner - Increase the critical hit chance of all attacks made against any target you have poisoned by 1,2,3%
 * Savage Combat - all physical damage caused to enemies you have poisoned is increased by 2,4%
 * Tricks of the Trade - Redirects all threat caused by the rogue's attacks to the targeted raid member for 5 seconds, and increases their damage by 15% during this time.

Shaman:
 * Earth Shield - healing and reduced spell interruption from damage for target
 * Water Breathing - target can breathe under water
 * Water Walking - target can walk on water
 * Bloodlust/Heroism - spell, ranged and melee haste
 * Elemental Oath - increased critical strike chance
 * Totemic Wrath - increased spell power while fire totem is active
 * Unleashed Rage - increase attack power
 * Ancestral Healing - decrease target's physical damage
 * Totem - Most totems affect the Shaman's party and last up to 5 minutes. Some of the totems don't apply buffs, but pulse benefits periodically.
 * Strength of Earth Totem - strength & agility
 * Elemental Resistance Totem - Fire, Frost and Nature Resistance
 * Windfury Totem - Increase melee haste
 * Flametongue Totem - additional spell power healing and damage
 * Stoneskin Totem - increase armor
 * Mana Spring Totem - mana regeneration
 * Wrath of Air Totem - spell haste
 * Grounding Totem - Redirects direct damage spell
 * Mana Tide Totem - short term Spirit multiplier
 * Healing Stream Totem - heals party
 * Earthbind Totem - Removes snares if talented
 * Tremor Totem - Removes fear, charm, and sleep

Warlock:
 * Unending Breath - underwater breathing for target
 * Demonic Pact - Adds a percentage of the Warlock's spell power to all party or raid members on minion crit
 * Imp
 * Blood Pact - stamina for Warlock's party or raid
 * Felhunter
 * Fel Intelligence - mana pool and mana regen

Warrior:
 * Battle Shout - agility and strength
 * Commanding Shout - stamina
 * Rampage - Increased Critical Strike chance

Consumable:
 * Blessing of Forgotten Kings (from - Weaker version of Greater Blessing of Kings, +8% to all stats, item is crafted by leatherworkers and usable by any level 80 character.
 * Gift of the Wild (from ) - Identical to druids' untalented max rank Gift of the Wild, item is crafted by leatherworkers and usable by any level 80 character.
 * Fortitude (from ) - Equivalent to untalented max rank Prayer of Fortitude, item is crafted by scribse and usable by any level 80 character.

By type
Similar buffs do not stack with eachother unless otherwise specified.

Physical damage buffs

 * +Agility and Strength
 * Death Knight: Horn of Winter
 * Hunter: (Pet) Cat/Spirit Beast: Roar of Courage
 * Shaman: Strength of Earth Totem
 * Warrior: Battle Shout


 * 10% Physical Haste
 * Death Knight: (Frost) Improved Icy Talons
 * Hunter: (Survival) Hunting Party
 * Shaman: Windfury Totem


 * 4% Physical Vulnerability
 * Death Knight: (Frost) Brittle Bones
 * Hunter: (Pet) Ravager: Ravage (pet)
 * Hunter: (Pet) Worm: Acid Spit
 * Rogue: (Combat) Savage Combat
 * Warrior: (Arms) Blood Frenzy


 * 10% Attack Power
 * Death Knight: (Blood) Abomination's Might
 * Hunter: (Marksmanship) Trueshot Aura
 * Paladin: Blessing of Might
 * Shaman: (Enhancement) Unleashed Rage


 * 12% Armor Debuff
 * Druid: Faerie Fire
 * Hunter: (Pet) Raptor: Tear Armor
 * Hunter: (Pet) Serpent: Corrosive Spit
 * Rogue: Expose Armor
 * Warrior: Sunder Armor


 * 30% Bleeding Damage increase
 * Druid: (Feral) Mangle (Bear Form) (Bear Form) / Mangle (Cat Form) (Cat Form)
 * Hunter: (Pet) Hyena: Tendon Rip
 * Hunter: (Pet) Boar: Gore
 * Rogue: (Subtlety) Hemorrhage
 * Warrior: (Arms) Blood Frenzy

Universal buffs

 * 5% Critical bonus
 * Druid: (Feral) Leader of the Pack
 * Hunter: (Pet) Devilsaur: Terrifying Roar
 * Hunter: (Pet) Wolf: Furious Howl
 * Rogue: (Subtlety) Honor Among Thieves
 * Shaman: (Elemental) Elemental Oath
 * Warrior: (Fury) Rampage


 * 5% Increased stats
 * Druid: Mark of the Wild
 * Hunter: (Pet) Shale Spider: Embrace of the Shale Spider
 * Paladin: Blessing of Kings


 * 3% Increased damage
 * Hunter: (Beast Mastery) Ferocious Inspiration
 * Mage: (Arcane) Arcane Tactics
 * Paladin: (Retribution) Communion


 * 30% Haste
 * Hunter: (Pet) Core Hound: Ancient Hysteria
 * Mage: Time Warp
 * Shaman: Heroism/Bloodlust

Magic damage buffs

 * 8% Magic Damage taken debuff
 * Death Knight: Ebon Plaguebringer
 * Druid: (Balance) Earth and Moon
 * Hunter: (Pet) Dragonhawk: Fire Breath
 * Hunter: (Pet) Wind Serpent: Lightning Breath
 * Rogue: (Assassination) Master Poisoner
 * Warlock: Curse of the Elements


 * 6% Spell Power
 * Mage: Arcane Brilliance/Dalaran Brilliance
 * Shaman: Flametongue Totem


 * 10% Spell Power
 * Shaman: (Elemental) Totemic Wrath
 * Warlock: (Demonology) Demonic Pact


 * 5% Spell Haste
 * Druid: (Balance) Moonkin Form
 * Priest: (Shadow) Shadowform
 * Shaman: Wrath of Air Totem


 * 5% Spell Critical debuff
 * Mage: (Fire) Critical Mass
 * Warlock: Shadow and Flame

Mana buffs

 * Increased mana pool
 * Mage: Arcane Brilliance/Dalaran Brilliance
 * Warlock: (Pet) Felhunter: Fel Intelligence


 * Increased mana regeneration
 * Paladin: Blessing of Might
 * Shaman: Mana Spring Totem
 * Warlock: (Pet) Felhunter: Fel Intelligence


 * Replenishment
 * Druid: (Restoration) Revitalize
 * Mage: (Frost) Enduring Winter
 * Paladin: (Retribution) Communion
 * Priest: (Shadow) Vampiric Touch
 * Warlock: (Destruction) Soul Leech

Survivability buffs

 * Increased health pool
 * Hunter: (Pet) Silithid: Qiraji Fortitude
 * Priest: Power Word: Fortitude
 * Warlock: (Pet) Imp: Blood Pact
 * Warrior: Commanding Shout


 * Increased Armor
 * Paladin: Devotion Aura
 * Shaman: Stoneskin Totem


 * Reduced physical damage
 * Priest: (Holy) Inspiration
 * Shaman: (Restoration) Ancestral Healing


 * Increased resistances
 * Druid: Mark of the Wild
 * Hunter: Aspect of the Wild (Nature resistance)
 * Paladin: Resistance Aura (Shadow, Fire, and Frost resistance)
 * Priest: Shadow Protection (Shadow resistance)
 * Shaman: Elemental Resistance Totem or Glyph of Healing Stream Totem (Fire, Frost, and Nature resistance)

Lordaeron's Blessing
Increases stamina by 5%.

Lasts: 30 min

How to get: Take control of the northpass tower in Eastern Plaguelands, click the altar that appears outside the door.

Notes: Persists in Scholomance and Stratholme, and persisted in the original Naxxramas.

Fire Resist
Increases fire resistance by 83.

Lasts: 1 hour

How to get: Mind Control (either by the Priest spell or the Engineering device) a Scarshield Spellbinder, found in Blackrock Spire.

Notes: Sometimes the tooltip will say differing amounts of Fire Resistance, but the buff always provides 83 resistance. Stacks with Paladin's Resistance Aura.

Rallying Cry of the Dragonslayer
Increases critical chance of spells by 10%, melee and ranged by 5% and grants 140 attack power, for characters below level 61.

Lasts: 2 hours

How to get: When the head of or  is returned the players located in (or nearby) Orgrimmar or Stormwind are buffed with this buff.

Spirit of Zandalar
Increases all stats for a value depending on level for 2 hours.

(Old Effect: Increases movement speed by 10% and all stats by 15% for 2 hours.)

Duration: 2 hours (As of 1.11, this buff no longer persists through death)

How to get: When the Heart of Hakkar is turned in to Molthor on Yojamba Isle as part of  quest, players on the Isle and in Booty Bay will receive the buff.

Warchief's Blessing
Blessing of the Warchief: Increases health by 300. 15% haste to melee attacks. 10 mana regen per tick.

Lasts: 1 hour

How to get: When the head of Rend Blackhand is returned after a player completes "For the Horde!", the end of the first part of the Onyxia prequest chain, all players located in Orgrimmar are buffed with this buff.

Songflower Serenade
Increases critical strike rating and spell critical strike rating by 70 and all attributes by 15.

Lasts: 1 hour

How to get: Cleanse a Corrupted Songflower in Felwood.

Buffs, debuffs, and raid stacking in WotLK
In the expansion, buff stacking and whether buffs affected the raid versus only the party were significantly changed. Here is the official release of this change from Blizzard on the forums: