What is the ACD file format?
The .acd file format is associated with ACID Pro, a loop-based audio workstation that provides tools for music production. The software also supports post-production of audio data, including effects processing and mix automation.
The .acd format stores all the data related to the project arrangement - track layout, loop events, BPM, key, effects chains, and envelope automation - along with references to external .wav, .mp3, and .ogg audio loop files. Note that audio is not embedded in the .acd file itself by default; a separate .acd-zip variant bundles the project and all referenced media into a single portable archive.
In order to open .acd files you need ACID software. There are different versions of ACID software - ACID Pro (professional) and ACID Music Studio (consumer) - and each uses the same .acd format for storing project information. The format is built on a RIFF container with ACID-specific named data chunks. The product passed through three owners: Sonic Foundry (1998), Sony Creative Software (2003), and MAGIX Software (2016), which currently publishes ACID Pro 11.
Security & safety
RISK: LOWACID project files are DAW session data; they do not execute code. Referenced external audio files should be from trusted sources.
Format details
in a nutshellPrograms that open ACD files
Windows2 apps
ACID Pro
Paid File → Open → select the .acd file. Ensure all referenced loop files are accessible at their original paths. 
Technical details
deep spec| Container | RIFF (Resource Interchange File Format) with ACID-specific named chunks |
| Magic bytes | RIFF (52 49 46 46) at offset 0; ACD-ZIP variant starts with PK (50 4B) ZIP signature |
| Byte order | Little-endian |
| Audio storage | External by default - project stores file paths to referenced WAV/MP3/OGG loops, not the audio itself |
| ACD-ZIP variant | .acd-zip extension; bundles project XML and all embedded audio into a ZIP archive for portability |
| Typical size | 5 KB - 500 KB (.acd alone); 10 MB - 2 GB (.acd-zip with embedded audio) |
| Loop metadata | ACIDized WAV loops carry embedded BPM and musical key metadata consumed by the project |
| Sample rate | Inherits from referenced audio loops; typically 44100 Hz or 48000 Hz |
| Platform | Windows only |
| Developer history | Sonic Foundry (1998-2003) → Sony Creative Software (2003-2016) → MAGIX Software GmbH (2016-present) |
| Current version | ACID Pro 11 (MAGIX, 2022+) |
| Product editions | ACID Pro (professional) and ACID Music Studio (consumer) - both use the same .acd format |
| Released | 1998 (ACID pH1, Sonic Foundry, Madison, Wisconsin) |
| Latest version | ACID Pro 11 (MAGIX, 2022+); format largely unchanged from RIFF base |
ACD conversions
Community Q&A
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