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

# Compress ISO or BIN/CUE to CHD online

Compress ISO or BIN/CUE disc images to CHD locally in your browser. Use this CHD converter without uploads or an account.

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## Table of contents

- [Add the disc](<#add-the-disc>)
- [Create the CHD](<#create-the-chd>)
- [Check compatibility and storage](<#check-compatibility-and-storage>)

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## Add the disc

1. Open [Compress](<https://rom-weaver.com/compress-files>).
2. Add the `.iso`, or add the `.cue` with every referenced `.bin` file.
3. Keep only that disc's files in **Inputs**.

Add a DVD-style ISO alone. For a CD, if `disc.cue` names `track01.bin` and `track02.bin`, add all three, including audio tracks. Keep filenames unchanged: the cue sheet names and orders them. Renaming BIN to ISO does not convert sectors. With a single `.iso`, **CHD** appears in **Output** only when the file's size is a whole number of 2048- or 2352-byte sectors. With a single `.bin`, it also needs the [content check](<https://rom-weaver.com/docs/supported-formats.md#container-and-compression-formats>) that marks a CD image. A cartridge `.bin` of a sector-aligned size gets only **ZIP** and **7z**. With a cue sheet, **CHD** is missing if you add a second sheet, an extra file the sheet does not name, or tracks with the same base name. An unaligned `.iso` still lists **RVZ**, which has no size check.

Compress creates only CD, GD-ROM, and DVD CHDs. It cannot create hard-disk or raw CHDs, so a hard-disk or raw `.bin` is not offered CHD, and an image with another extension or an unaligned size can only be added to a ZIP or 7z. A hard-disk or raw `.bin` can still become a CHD when you choose **CHD** as the Apply or Weave output. For the others, use the [native CLI](<https://rom-weaver.com/docs/work-with-archives.md#compress-a-rom-or-disc-image-instead>); [the formats reference](<https://rom-weaver.com/docs/supported-formats.md>) lists the exact rules.

## Create the CHD

1. In **Output**, choose **CHD**.
2. Enter the output filename without its extension.
3. Keep the default codecs, or open **Options** to change compression settings.
4. Select **Compress** and wait for the result.
5. Select **Download** and save the `.chd` file.

The output picker offers CHD only for compatible disc inputs. Changing an extension does not convert the disc.

If CHD is unavailable, remove unrelated files and check that every CUE track is present. Compress accepts one disc at a time.

For an image inside ZIP or 7z, add the archive to Compress. Select the ISO or the complete CUE/BIN set, then select **Add N files**.

## Check compatibility and storage

CHD can reduce disc storage while preserving the disc layout. Emulator support varies by system and emulator version.

Allow space for source, staged tracks, output, and download. Browser quotas and memory vary by device; compression savings are not guaranteed. For repeated memory/storage errors, use [native compression](<https://rom-weaver.com/docs/work-with-archives.md#create-a-chd-from-a-cuebin-set>).

Before deleting sources, extract the CHD and test it in your emulator. Compare DVD ISO checksums with [Checksum file](<https://rom-weaver.com/file-checksum>); compare CD tracks only with matching split/combined layouts. The [synthetic disc tutorial](<https://rom-weaver.com/docs/patch-compressed-disc.md>) supplies known bytes for practice.

To reverse this workflow, follow [Convert CHD to ISO, BIN/CUE, or GDI](<https://rom-weaver.com/docs/extract-chd.md>). [Choosing a compression format](<https://rom-weaver.com/docs/compression-formats.md>) compares CHD with RVZ and archives.