From Bulbapedia, the community-driven Pokémon encyclopedia.
HM moves, like Fly
, have effects outside of battle.
A Hidden Machine, HM for short (Japanese: ひでんマシン Secret Machine) is an item that, like a TM, is used to teach a Pokémon a move.
The difference between a TM and an HM is most pronounced in the earlier games in the series, where TMs were single-use items while HMs could be used an unlimited amount of times after they were obtained. HMs, unlike TMs, could not be sold for money, and the moves contained within could not be forgotten by Pokémon under normal circumstances. An HM move could be used by Pokémon even if they had fainted during battle.
All HM moves have the ability to be used outside of battle in the games they are HMs in, though a move's ability to be used outside of battle does not mean that it is necessarily an HM move. To be used outside of battle, specific Badges must be obtained by the player prior to Generation V to advance the game's storyline.
A Pokémon knowing an HM move cannot be sent forward from Generation III to Generation IV or from Generation IV to Generation V unless the HM move is deleted. Dive prevents sending forward from Pokémon FireRed and LeafGreen despite not being considered an HM by those games, while Defog and Whirlpool only prevent Pokémon being sent forward from the games they are an HM in. Pokémon with Whirlpool can freely be sent into Pokémon HeartGold and SoulSilver from Generation III, while Pokémon with Dive can freely be sent into Generation V games. In Generation V Pokémon knowing a HM move can not be traded via IR communications if it's in the party. This is because the player can trade via IR anywhere in game and could potentially get stuck somewhere that requires a HM move to escape.
In Generation I, five of the 165 moves are HM moves, and their use is essential for completing the game. Of these five, four of them remain as HM moves even in Generation V, while the fifth, Flash, retains the ability to be used outside of battle to light dark caves.
None of these moves are able to be forgotten in Generation I, and a Pokémon with these moves cannot be raised by the Pokémon Day Care on Route 5. Unlike in later generations, all of these moves must be selected from the Pokémon screen to be used.
In Generation II two new moves become HMs. The five from Generation I return, while a new move, Whirlpool, becomes one, and an old move, Waterfall, becomes another.
A Move Deleter was added to the games, mostly with the intention of making possible the ability to delete Generation II moves that a Generation I Pokémon had learned in order to be able to trade it back, though with the side effect of HM moves now being able to be forgotten.
From this generation on, Pokémon with HM moves are allowed in the Day Care, and fathers with HM moves will pass the moves down to their children as they would a TM move. HM moves can also be used just by checking the obstacle that the HM will clear, such as surfable water or a movable rock.
In Hoenn one of the Generation II HMs lost its status, while another move became the eighth HM.
In Kanto, due to a lack of use for Dive, HM08 is unobtainable and can only be accessed through cheating. The first five HMs can be acquired through the same methods as in Generation I, while HM06 and HM07 can be found in the Sevii Islands later in the game.
In Sinnoh, for the first time, one of the original HMs lost its status to a new move, while HM08 was brought back as a different move.
Johto and Kanto
Defog lost its HM status in Johto for the return of Whirlpool; all other HMs retained their status from Sinnoh games.
HMs were reduced to 6 in Generation V; HM07 and HM08 no longer exist in the coding of Pokémon Black and White. Dive returns for use in Unova. This is the first time HM moves do not require Gym Badges for use outside of battle. Although most HM moves cannot be obtained before earning certain Gym Badges, if the player obtains a Pokémon that has learned an HM move through other means (via level-up, trading, etc.) the player will be able to use the HM in the field without restrictions.
When a move is replaced by an HM, the HM move takes on the current PP of the replaced move until healed or replenished. The same also applies for replacing old moves with TMs.
- In Generations I, II and V, all HMs only have one word in their names.
- Also, the only two HMs to date that have more than one word in their names are the only two to include "Rock" in their names despite not being Rock-type.
- Rock Smash is the only HM with a unique type. All other HM moves share their type with at least one other HM move, while the Water type is represented by four different HM moves (though only three were ever HMs concurrently).
- Tracey's Scyther is the first Pokémon belonging to a main character of the anime to have used a current HM move, Cut. It wasn't until the Diamond & Pearl series that one of Ash's Pokémon use a current HM move; Ash's Grotle uses Rock Climb.
- Though debatable, other Pokémon may have used Surf, Dive and Fly throughout the anime; although, they were not directly ordered to use the move.
- The only current HM moves that are able to be learned by Pokémon by level-up are Fly, Waterfall, and Dive. Former HMs Flash, Whirlpool, Defog, Rock Smash, and Rock Climb, are also learnable by level, but only since their loss of HM status. Moves that regain their HM status, like Whirlpool and Dive did, remain learnable by level-up. Waterfall remains the only HM move that has been learnable by level-up since it was introduced as a move, prior to gaining HM status.
- In Generation IV, all moves that were at one time an HM are learnable, with Flash available by TM70 and Dive available by Move Tutor. Defog and Whirlpool, which replace each other in the Sinnoh- and Johto-based games, are both HM05.
- Generation IV is the only generation in which two moves share the same HM number.
- HM moves have so far been only of the Flying, Fighting, Water, and Normal types.
- The only HM moves that are status moves so far are related to accuracy: Flash decrease the foe's accuracy while Defog decrease the foe's evasion.
- In HeartGold and SoulSilver Versions, on Route 20, a Trainer states "Surf is no longer the only HM move you use in water" when he is defeated. This is a reference to Generation I, where the only HM usable in the water was Surf.
- The only way for the player to delete an HM move in the handheld games is to use the Move Deleter. Note that "HM moves" are not always HMs in every game, and can be replaced freely in games where they are not HMs:
- Pokémon Stadium 2, Pokémon Colosseum and Pokémon XD allow any move to be replaced.
- Pokémon FireRed and LeafGreen allow Dive to be forgotten.
- Pokémon Diamond, Pearl, and Platinum allow Dive, Flash, and Whirlpool to be forgotten.
- Pokémon HeartGold and SoulSilver allow Defog, Dive, and Flash to be forgotten.
- Black, White, Black 2, and White 2 allow Flash and Rock Smash to be forgotten.
- A Pokémon knowing an HM move that is left in the Day Care may forget the HM move in favor of a new move; see Day Care.
- The HM moves Cut, Fly, Surf and Strength have been in every main-series Pokémon game. Out of these, only Fly is able to be learned in any way aside from using the HM.
- Generation V is the first generation to have fewer HMs than the preceding generation.
- The Mineral Badge of Johto is the only Badge, prior to Generation V, which does not enable the use of an HM in any game it is present in.
- The only former HM that remains a move usable on the field in games it is not an HM in is Flash, which to this day can be used to light up caves.
- Dive is the only HM in Generation V that is not found in a different location between Black & White and Black 2 & White 2.
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