Is the shininess always determined when the egg is generated?

Question

I know similar questions have been asked similarly a billion of times, but I come bearing new info.

I was watching this video, and at 32:40 onwards, he says, “save here. When you receive this egg, it will hatch shiny. the egg is done generating at this point”. Followed by, “We’re going to confirm the it’s shiny by hatching it, and then we’re going to turn off the game. That’s why we saved in front of the old man”. He later says, “it will stay shiny as long as you don’t receive it or reject it from him.”

I always thought that shininess was determined as you receive the egg, not ans it’s generated. and I’m sure other answers say that as well. Is this only the case for RNG HGSS, or is there other cases this applies to?

Basically, how and why does this happen?

I’d like a full comprehensive guide and I’d appreciate it if you worded it like you were talking to a 7 year old.

Comments

@Monkey That was gen 7, not HGSS.

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Some clarity for the above comments:
- A shiny egg may not hatch shiny after being traded because shiny trait is a function of the egg's PID and the TSV of the trainer who hatches it. So if the trainer hatching the egg has a different TSV (4095/4096), then the egg won't be shiny. This has nothing to do with when the PID is generated, except in Gen 8+ where the game re-rolls the PID for every traded egg.
- The parent-replacing trick happens because of how Gen 7 seeds its RNG, which doesn't have much to do with when the game pulls a PID out of the RNG.
- In Gen 8, determining shininess is the only responsibility of the PID. Other traits like nature, etc are independent from it. So you would literally need to hatch a shiny, then hatch it again between resets to make conclusions about PID generation in those games.

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No, shininess is determined when the egg is generated in HGSS. There's no doubt about that.
If you're doing manip after the egg is generated, you are trying to get good IVs. IVs are set when you pick up the egg and are independent from the PID.

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Oh, gotcha. This is a new topic for me

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Ok so I actually tried DMing the guy from the video on Twitter to answer this question, and he could not have been more rude.

Me:
Hey, so basically I'm trying to answer this question on the Pokemon Database

https://pokemondb.net/pokebase/418887/is-the-shininess-always-determined-when-the-egg-is-generated

And I know from your video linked in the question that at least in HGSS, shininess from a Pokemon is determined when the egg is generated. Is this the case for all games? And if not, which games don't follow this usage of RNG?
10:58 AM
Him:
it very much depends on the game
All gen 4 games do it this way
11:01 AM
it doesnt really matter if you're just a shiny hunter
11:04 AM
Me:
Just for the sake of the question does this only happen in Gen 4?
12:29 PM
no
If you're not rnging, it doesn't matter.
What's the purpose of the question
12:48 PM
Me:
The purpose of the question is to know when shininess is generated in all main series games when receiving an egg
2:11 PM
Him:
Spend the time learning all the rng in those games then lol.

Followed by a block...

What a jerk