Depositing any Pokémon into HOME for the first time will assign it a HOME tracker value, a 64-bit number unique to it that is used to detect clones and other hacked Pokémon. (For example, a Pokémon hacked to have a random tracker value can be detected as HOME will not remember having assigned this value in the past.) This tracker value is stored with the Pokémon and stays the same even if (e.g.) the Pokémon is withdrawn and traded offline to another player.
As of v2.0.0, the tracker value is also used to keep track of data that is not transferred between games and must be stored server-side, such as:
- A Pokémon's three movesets (between Sword and Shield, Brilliant Diamond and Shining Pearl and Legends: Arceus)
- Met location and egg hatch location (since none of the three sets of games share location index numbers)
- Gigantamax Factor, Technical Record flags, Sociability, effort levels, Alpha flag, and Zisu's Move Tutor moves and Move Mastery flags
For example, the Alpha Pokemon flag is not stored anywhere in the Pokémon data of Sword/Shield or Brilliant Diamond/Shining Pearl. If a Pokémon from Pokémon Legends: Arceus is transferred to one of these games and back, it must keep its Alpha flag. This is done by HOME associating that flag with that Pokémon's HOME tracker value. (The tracker value is also used for the once-per-save-file restriction on newly depositing certain Legendary/Mythical Pokémon from Brilliant Diamond and Shining Pearl. A Pokémon is being newly deposited if it does not have a HOME tracker value.)
Effectively, HOME as of v2.0.0 keeps track of three sets of incompatible data for each Pokémon; however, only one set of data will be displayed when a Pokémon's summary is viewed in HOME. For example, the Legends: Arceus set of data will display significantly different stats and no Ability compared to the other two sets of data (even though the Ability is internally remembered by Legends: Arceus and is not game-specific data). On the Nintendo Switch version, only the Sword/Shield set of data will be displayed for all Pokémon unless the application is currently connected to Brilliant Diamond/Shining Pearl or Legends: Arceus. The type of Poké Ball shown will change depending on which set of data is being displayed, though the origin mark will always be correct. On the mobile version, the set of data displayed for a Pokémon is picked depending on the last game it was previously in (or Sword/Shield by default if that Pokémon has never been in a Generation VIII game). The type of Poké Ball shown will always be correct.
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If HOME attempts to display (for example) the Sword/Shield set of data for a Pokémon incompatible with Sword/Shield, the results vary depending on version. On the mobile version of HOME, this can only happen if a Pokémon incompatible with Sword/Shield is transferred from Bank or GO, and the app will display the stats and moveset as they last were in Bank (or as determined by GO Transporter). On the Nintendo Switch version before v2.0.0, the application behaved identically to the mobile version. On the Nintendo Switch version from v2.0.0 onward, the app will not display any stats or moves for incompatible Pokémon.