Learn how to duplicate items with our step-by-step guide for Animal Crossing: New Horizons (ACNH) on the Nintendo Switch. Read on for more information about the glitch with our guide below!

What is the Mailbox Duplication Glitch?

Users have been sharing duplication glitches for 1x1 and 2x1 items, but recently, Youtube user Do Whatever Games shared a video on how to duplicate almost any item, including rare materials such as Gold Nuggets and Large Star Fragments, and even up to valuable items, such as works of art and Nook Miles Tickets, using the game's mail system.

Basically, any item that can be attached to a letter can be duplicated.

Take note that this is a glitch not intended by the developers and may be taken out in future updates.

How to Do the Mailbox Duplication Glitch

Steps to Duplicate Items

Steps
1	Have 3 player accounts on your island. Create 2 more profiles if you don't have them.
2	If you have moveable mailboxes, place them near Resident Services.
3	Have Player 1 send the mail to Player 2 with the items to be duplicated attached. We reccomend sending only 3 to 5 items at a time.
4	Start Party Play by calling Player 2, and swap leaders.
5	Have Player 2 enter and exit a building for the mail to load in.
6	Swap leaders with Player 1 and end co-op session.
7	Restart Party Play by calling Player 2 and swap leaders.
8	Have Player 2 open the letters and grab the presents. Do not open the presents and drop the items on the ground yet.
9	Swap leaders with Player 1, and press the - button to pick residents again.
10	Select Player 3, and end the session when possible.
11	Repeat steps 7 to 10, the mail should be unopened and you can get the attached presents every time.

1. Have 3 player accounts on your island

If you're playing by yourself, create two more Switch profiles and add them to your island.

2. Move mailboxes near Resident Services

This is not required, but we recommend having moveable mailboxes so you can place them near Resident Services.

The reason for this is that every time you start co-op mode (Party Play), you will always be taken to the Plaza. This way, you can access the mailbox faster and not risk having the game save at crucial times.

3. Have Player 1 send the mail to Player 2 with the attached items

Use Player 1 to send letters with the items to be duplicated attached to Player 2. We recommend sending only 2-5 items at a time, to be able to do the glitch successfully.

4. Call Player 2 to the game and swap leaders

Now, start co-op mode (Party Play) by selecting to call a resident on your NookPhone, and select Player 2.

You will be redirected to the Plaza to configure the controllers. After that, shake Player 1's controller to swap leaders and press A on Player 2's controller to confirm.

5. Have Player 2 enter and exit a building for the mail to load in

You can fast-forward 1 day after sending the mail to have it delivered. Alternatively, you can use Player 2 to enter or exit any building, so that the mail loads into their inbox.

6. Swap leaders with Player 1 and end the co-op session

Shake Player 3's controller to swap leaders with Player 1. Using Player 1's character, press the - button to end the session.

7. Restart Party Play by calling Player 2 and swap leaders

Restart co-op mode by calling Player 2 again, and make them the leader. Now, this is where the race against the autosave time starts.

8. Have Player 2 open the letters and grab the presents

Run to your mailbox to open the letters and get the presents. This is why we recommend moving the mailbox near Resident Services, so you can access it right away.

Do not open the presents and drop the items on the ground yet. You can do this later on when your inventory is full.

If the game saves after opening the letters, the glitch will not work and you have to restart the whole process. The game saves at the start of the session, and then every 3 minutes. You can set up a timer on your phone if it helps you track the time.

9. Swap leaders with Player 1, and press the - button to pick residents again

Once putting all the presents in your pockets, swap leaders with Player 1 again. Player 1 will press the - button and select Pick residents again among the options.

10. Select Player 3, and end the session

This time, call Player 3. After doing the controller configuration, there is no need to swap leaders.

Press the - button and choose to end the session.

11. Repeat steps 7 to 10 to infinitely open letters

Repeat steps 7 to 10, starting from calling Player 2, getting the presents, and ending the co-op session with Player 3.

The mail should be unopened and you can get the attached presents every time. If not, then you might have done something wrong, and you need to restart the whole process.

Make sure that the game saves before opening the mailbox. If the game saves after, the glitch will not work.

Recommended Items to Duplicate

You can duplicate any item you want including expensive clothing and furniture, but we recommend duplicating items and materials that are difficult to get.

Reccomended Items to Duplicate
DIY Recipes Rare crafting materials: Large Star Fragments, Gold Nuggets Often-used crafting materials: Wood, Stone, Iron Nuggets Seasonal crafting materials: Acorns, Pinecones, Cherry-Blossom Petals, Mushrooms Nook Miles Tickets Fish Bait (No more crafting!) Works of Art (Large or Wall-Mounted) Large Furniture from Gulliver (that cannot be duplicated with the 1x1 or 2x1 item glitch)

Items You Cannot Duplicate

You cannot do this glitch on items that cannot be attached to letters. These include:

Items that Cannot be Attached to Letters
Bugs Fish Flowers (The dug up plant, you can send petals) Trees Shrubs/Bushes Rusted Parts

Frequently Asked Questions (FAQs)

How Long is the Auto-Save Timer?

The game auto-saves every 3 minutes. The game will also save when using features such as sending mail and starting Party Play.

Why Am I Not Receiving Letters?

Usually, letters are sent the next day, but you can force mail to be delivered by fast-forwarding one day.

Alternatively, while using the player's profile, you can enter a building to refresh the mailbox so any sent mail will load in.

Can I Do This On a Switch Lite?

As long as you have an extra controller like a JoyCon or a Switch Pro Controller, you can do this glitch. The Switch Lite's built-in controllers do not work.

If not, then there is no other way to do this as of now, as you need another controller to be able to play co-op (Party Play).

You Can Do This With a Regular Switch

Just separate the two JoyCons in your Switch so that you have 2 controllers.

Can I Do This Glitch With Only One Player?

Currently, you cannot do this with only one player. You need 2 extra players on the island to recreate this glitch as it uses the mail system and Party Play.

Can I Delete the Other Players After?

You can delete the other players on your island by starting the game using their profile, and pressing the - button to go to the game settings. From there, you can delete that the player from the island.

How to Add or Delete Players

Patch Updates

Patched in the V 1.2.1 Update

As of May 21, 2020, a new update is available to download via the Internet, which fixes all the glitches found in the V 1.2.0 update of the game.

How to Update and Update Patch Notes

Punishment and Repercussions

“Fixed a serious bug affecting game balance.”
Source: Nintendo's Patch Notes re: V1.1.1 Update

Players who did the duplication glitches were not punished for abusing it. All the items and Bells gotten through this glitch remained in their inventories. However, some have noted that they have lost items along the way while recreating this glitch. Only do this at your own risk!

Related Guides

Head Back to News & Updates

DLC and Event Updates
List of New Features	List of New Horizons DLC
April Ver 1.2 Update	July Ver 1.3 Update
August Ver 1.4 Update	September Ver 1.5 Update
November Ver 1.6 Update	January Ver 1.7 Update
February Ver 1.8.0 Update	1st Anniversary Event
March Ver 1.9.0 Update	April Ver 1.10.0 Update
April Ver 1.11.0 Update	ACNH Direct and November Update
Nintendo Switch Online + Expansion Pack	November Ver 2.0.1 Update
November Ver 2.0.2 Update	November Version 2.0.3 Update
December Ver 2.0.4 Update
Merchandise and Promotions
Sanrio amiibo Pack	Build-A-Bear Collection
How to Use the Island Tour Creator	Original Soundtrack and Sheet Music
UNIQLO Collection	PUMA x ACNH Collab
Bugs and Patch Updates
Maintenance | Fix Errors	How to Update and Update Patch Notes
Game Glitches
How to Climb the 4th Cliff Level	How to Plant Trees on Clifftop Edges
1x1 Item Duplication Glitch [Fixed]	2x1 Item Duplication Glitch [Fixed]
Mailbox Item Duplication Glitch [Fixed]	How to Plant Trees on Paths [Fixed]
How to Swim in Rivers | How to Sit in Pools	How to Center Items on Tables Outside
Pre-Release Content
Animal Crossing Direct	Is there a Demo?
Pre-order Bonuses	Giveaways
How to Pre-load