Canonical: https://rom-weaver.com/docs/convert-to-z3ds

# 3DS to Z3DS and ZCCI: compress 3DS ROMs online

Compress `.3ds`, `.cci`, `.cxi`, `.cia`, `.3dsx`, or `.app` files locally in your browser. Most types keep a matching extension, such as `.cci` to `.zcci`; `.app` becomes `.zcxi`. Files stay on your device.

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<!-- START doctoc -->
## Table of contents

- [Add the Nintendo 3DS file](<#add-the-nintendo-3ds-file>)
- [Create the compressed file](<#create-the-compressed-file>)
- [Check the result](<#check-the-result>)

<!-- END doctoc -->

## Add the Nintendo 3DS file

1. Open [Compress](<https://rom-weaver.com/compress-files>).
2. Add one `.3ds`, `.cci`, `.cxi`, `.cia`, `.3dsx`, or `.app` file to **Inputs**.
3. Remove other files before choosing the output format.

For a ROM inside ZIP, 7z, or an existing compressed 3DS file, add that file to Compress. Select the ROM, then select **Add N files**.

## Create the compressed file

1. In **Output**, choose **Z3DS**.
2. Enter the output filename without its extension.
3. Keep the default compression level, or open **Options** to change it.
4. Select **Compress** and wait for the result.
5. Select **Download** and save the compressed file.

The Z3DS option covers every supported 3DS subtype. For example, a `.cia` input produces `.zcia`, while `.3dsx` produces `.z3dsx`.

Keep the extension assigned by Compress. The [Z3DS filename reference](<https://rom-weaver.com/docs/supported-formats.md#z3ds-filename-variants>) lists each mapping.

If Z3DS is unavailable, check the input extension and keep only one file in **Inputs**. Changing an extension does not convert the contents.

## Check the result

Test the compressed file in an emulator that supports its Z3DS subtype. Keep the original until you check the result.

To check the uncompressed bytes, [extract the compressed file](<https://rom-weaver.com/docs/extract-z3ds.md>). Compare its checksum with the original through [Identify](<https://rom-weaver.com/docs/identify-roms-browser.md>).

Keep enough free storage for the original and compressed output. Compression does not decrypt a ROM or convert a CIA package into a cartridge image.

[Choosing a compression format](<https://rom-weaver.com/docs/compression-formats.md#3ds-rom-compression-z3ds>) explains Z3DS compatibility. For GameCube and Wii discs, use [ISO to RVZ](<https://rom-weaver.com/docs/convert-to-rvz.md>).