Summary of "INFINITE ITEM DUPLICATION IN POKÉMON FIRERED & LEAFGREEN NINTENDO SWITCH VERSION (MAIL GLITCH)"

Mail glitch (Pokémon FireRed / LeafGreen) — Infinite item duplication

This guide summarizes a video tutorial showing how to set up the classic “mail glitch” in Pokémon FireRed / LeafGreen (Nintendo Switch and Switch 2 versions) to infinitely duplicate any item. It covers prerequisites, the in-battle corruption sequence, and the PC/party steps to generate extra copies of held items.

Prerequisites

Progress far enough to reach “Silon City” (subtitle likely intended “Saffron City”).
Retro Mail purchased from the department store (first floor). The tutorial buys a stack (99).
A Pokémon that knows Recycle (example: Mr. Mime ~level 33).
A Pokémon that knows Knock Off (example: Farfetch’d ~level 21).
A battle‑consumable berry (example: Citrus Berry or Autumn Berry).
Versus Seeker available if you need to re-fight trainers.

Party setup (before the battle)

Prepare a party of three Pokémon:

Pokémon A — holds the berry. Make sure its HP is below 50% so the berry will be consumed during battle.
Pokémon B — Farfetch’d (knows Fly and Knock Off).
Pokémon C — Mr. Mime (knows Recycle). Give Mr. Mime a Retro Mail containing a single word (example: “Abra”).

Set up the mail glitch (combat steps)

Go to the left of Silon City and start a double battle (can be a re-fight).
Turn 1:
- With the left-side Pokémon (A) use a normal attack.
- Use Fly with Farfetch’d so it avoids damage that turn.
- End of the turn: the berry on Pokémon A should be consumed (HP < 50%).
Turn 2:
- Optionally KO one opponent Pokémon if desired.
- Wait for Farfetch’d to land after Fly.
- Switch your left Pokémon into Mr. Mime (Mr. Mime enters on the left slot).
- Use Knock Off with Farfetch’d targeting your partner — the double-battle targeting causes Knock Off to hit Mr. Mime and remove Mr. Mime’s Retro Mail in an unintended/corrupted way.
Next turn:
- Use Recycle with Mr. Mime. Instead of returning the removed Retro Mail, the game will refund the consumed berry.
- Finish the battle. The mail glitch is now set.

Using the glitch to duplicate items (PC / party steps)

Go to a PC/box screen.
Fill your party with six Pokémon.
Give Retro Mail containing the same single word (e.g., “Abra”) to the first five Pokémon.
Attempt to give Retro Mail to the sixth Pokémon. If the glitch is active:

You will see three question marks appear in every slot.
- Back out immediately; do NOT complete assigning the mail to the sixth Pokémon. 5. Instead, give the sixth Pokémon the item you want duplicated (example: Nugget) as its held item. 6. If done correctly, the mail won’t replace the held item, and you will find an extra copy of that item in your bag. This works with any in-game item.

Key tips and notes

Ensure the berry will be consumed in battle (left Pokémon HP < 50%).
Use Fly to keep Farfetch’d safe until the moment you need it to hit Mr. Mime.
The signature indicator the glitch is ready: the three question marks when attempting to give mail to the sixth party slot.
Do not actually assign the mail to the sixth Pokémon — back out and give the item you want duplicated instead.
The tutorial claims this method works on Nintendo Switch and the next Switch version of FireRed/LeafGreen.
Subtitles in the video contain some typos (e.g., “Retro male,” “Mr. May,” “Silon City”); those have been corrected above where obvious.