View source for List of revision differences in the core Pokémon games

{{summary page}}
There have been multiple revisions of a number of core series Pokémon games. These revisions may have been created for purposes such as removing bugs and refining the game's code/features.

==In Generation I==

===Japanese Red, Green, Blue, Yellow cartridges===
Pokémon Red and Green have two revisions, the first revision and revision A (also known as v1.1). Pokémon Blue has only one known revision, and Pokémon Pikachu appears to have as many as four different revisions (known as v1.0, Rev A, Rev B and Rev C).

====Differences====
=====Japanese Red/Green=====
#The [[closed menu Select glitch]] is possible in the original revision of Pokémon Red and Green (v1.0) by pressing Select on an item from within battle, pressing B once and then entering the Pokémon or moves screen to swap an unintended Pokémon or move. In Rev A, this was fixed although it is still possible to perform a closed menu Select glitch by pressing Select outside of a battle before entering a battle or bringing up the Pokémon menu through another means (Day Care, Name Rater or Cerulean City badge man).
#Unintentionally, the [[glitch item]] "Gold Badge" (Japanese: ゴールドバッヂ) has a different effect in Red and Green Rev A (as well as Japanese Blue); where it will only make the menu invisible instead of bringing up a visible glitch mart.
#Unintentionally, the [[arbitrary code execution]] glitch item "てへ" (hex:7B) is an unterminated name glitch item in Rev A of Pokémon Red and Green but not v1.0. This means that a [[0x50 tile]] must appear in an early position of the screen before using the glitch item in Rev A to prevent corruption or a potential freeze.
#Locations of internal functions in the ROM were changed.

=====Japanese Yellow=====
#Locations of internal functions in the ROM were changed.

====Imprints====
There is a way to tell the difference of a physical cartridge by looking for an imprint on the bottom right corner of the cartridge. This imprint can be difficult to see unless light is shined onto it. Below is a table of imprints mainly courtesy of the Japanese website [http://hakuda2.web.fc2.com/wario/poke1/c5.html Legendary Star Blob].

{| class="wikitable"
!  !! Initial version !! Later version
|-
| <span style="color:red;">Red (two versions)</span> || 00, 20, 22 || 00A, 12A, 20A, 22A, 34A
|-
| <span style="color:green;">Green (two versions)</span> || 00, 20 || 00A, 11A, 12A, 20A, 22A, 1M
|-
| <span style="color:blue;">Blue (one version)</span> || 00, 12, 20, 22 || (No later version known)
|-
| <span style="color:orange;">Yellow (four versions)</span> || 00, 20, 22 || 00A, 00B, 00C, 11D, 12A, 12B, 12C, 12D, 20A,　 20C, 22A, 22B, 22D, 22E, 34D
|}

===Virtual Console Red, Green, Blue, Yellow games===
====Red/Blue/Yellow====
#The animations of moves Blizzard, Bubble Beam, Confusion, Dream Eater, Explosion, Guillotine, Hyper Beam, Mega Kick, Mega Punch, Psychic, Reflect, Rock Slide, Self-Destruct, Spore, Thunderbolt were changed to reduce flashing lights in the interest of safety of people with photo-sensitive epilepsy.
#Jynx's sprite was changed in international Pokémon Yellow to have its face changed from black to purple, closer to its current design since the early 2000s. This was a reaction to criticism of the Pokémon for promoting a racial stereotype.
====Yellow only====
#A Pikachu belonging to the player character no longer needs to know Surf to unlock and play the Route 19 Summer Beach House minigame Pikachu's Beach, but due to a possible glitch, the posters which give tips and the Dude's scribbles will still only update if the Pikachu knows Surf.
#The Print function is the Pokédex was altered to do nothing other than play the 'selected' sound effect, similar to what happened with the Virtual Console release of Super Mario Bros. Deluxe. <!--and Link's Awakening??; confirm-->
#Attempting to print a box will make the cursor white and play the printer music, but not bring up a printer error message. The music will play until B is pressed.
#Attempting to print the diploma for completing the Pokédex in Celadon Mansion will bring it up and play the printer music, but not bring up a printer error message. This may cause music to overlap on itself after the diploma screen is exited. 
#Attempting to have the Pokémon Fan Club chairman in Vermilion City print the status of a Pokémon in the party will bring up its stats and play the printer music but not bring up a printer error message.
#Attempting to print the hi-scores for Pikachu's Beach using the Summer Beach House printer in Route 19 (requires a Pikachu belonging to the player in the party) will bring up the certificate and play the printer music but not bring up a printer error message.

====Behavior of the Virtual Console====
#The game is able to be paused on the Touch Screen, but restore points cannot be created (unlike other Virtual Console releases) possibly as an attempt to prevent/reduce Pokémon cloning.
#A Wireless Trading feature was introduced replacing the ability to communicate via Link Cable. After talking to the Cable Club lady, the player is able to act as a host and invite another player to communicate with in the Trade Center or Colosseum.
#The Virtual Console will ignore unknown opcodes, allowing for particular glitch effects to function differently in the Virtual Console releases, including the effects of glitch moves [[AttackDex/RB:168|Super Glitch A8]] in English Red and [[AttackDex/Y:238|TM38]] (move 0xEE) in English Yellow, which both enable the player to partially escape from a wild Pokémon battle or restart a Trainer battle. Super Glitch A8 will place the player in a Glitch City but not change the map ID, while TM38 will place the player somewhere in Professor Oak's lab.

==In Generation II==

===English Pokémon Crystal===
The English version of Pokémon Crystal has two revisions, v1.0 and Rev A.

====Differences====
#Rev A of the game added a Pokédex page number variable (controlled by bit 0 of address C7E5), ostensibly fixing a possible glitch. In v1.0, this was controlled by address CF65 instead, which is also an address that is written to when the player's badges animate on the Trainer Card.  
#The tilemap for the untranslated Mobile Stadium 2 Link is corrupted in Rev A, and this is possibly unintentional. The corruption is due to 0x0A bytes being converted into 0x0D 0x0A bytes, as if they were Unix newlines converted into Windows newlines. 
#Alteration of a delay loop. {{clarify}}

==In Generation III==

===Pokémon Ruby and Sapphire===
Pokémon Ruby and Sapphire have three differences, v1.0, Rev A and Rev B.

====Differences====
The most well-known change is the developers fixing a typo where Mawile in the Pokédex is referred to as "MAWHILE".

(See this forums thread for more differences, for now: http://forums.glitchcity.info/index.php?topic=7211.0).

===Pokémon FireRed and LeafGreen===
Pokémon FireRed and LeafGreen have two differences, v1.0 and Rev A.

====Differences====
#The initial version is affected by the [[Pokédex category glitch]] in which Pokémon with categories that are two words long have their categories shortened to only one word (e.g. "TINY BIRD" becomes "TINY" Pokémon. Rev A fixes the glitch to display the intended category.