What is the DAD file format?
The .dad file is a Chromeleon Channel Raw Data file produced by the Dionex Chromeleon Chromatography Data System (CDS), now developed and maintained by Thermo Fisher Scientific. "DAD" stands for Diode-Array Detector - the UV/Vis detector type most commonly used in HPLC (High-Performance Liquid Chromatography) workflows.
During a chromatography run, the Chromeleon software captures the raw signal from each detector channel and saves it as a separate binary file. The .dad file specifically stores the raw absorbance trace from a diode-array detector, recording signal intensity over time at one or more wavelengths.
The format is proprietary and binary (little-endian), with no publicly documented magic bytes or open specification. .dad files are not standalone documents; they live inside a Chromeleon datasource or sequence folder alongside companion files such as .seq (sequence), .qnt (quantitation), and .cmbx metadata files. In regulated laboratory environments (21 CFR Part 11), data integrity and audit-trail controls are enforced at the Chromeleon datasource level rather than inside the .dad file itself.
File sizes typically range from tens of kilobytes to a few megabytes per channel, depending on the detector sampling rate set in the Chromeleon method and the total run length.
Chromeleon 7.x shifted toward a managed repository model, making loose .dad channel files less common in newer installations. To open or export .dad data, Thermo Scientific Dionex Chromeleon CDS is required; data can be exported to a CDF or CSV for use in third-party tools.
Security & safety
RISK: LOWA Chromeleon .dad is proprietary instrument data, not an executable, so it carries little direct risk. In regulated labs the real concerns are data integrity and access control: handle .dad files within Chromeleon's managed datasource and audit trail (21 CFR Part 11), don't alter raw data outside the system, and keep backups. There is no legitimate generic "DAD opener" - be wary of download portals claiming otherwise.
Format details
in a nutshell- FontLab database (FontLab Studio) - FontLab has used .dad for internal font/database data; unrelated to chromatography.
- Oracle SQL*Loader data file (informal) - A .dad is sometimes a SQL*Loader input data file, though .dat/.ctl are the usual extensions.
- Oracle Application Server DAD config (legacy) - Oracle mod_plsql 'Database Access Descriptor' (DAD) configuration in older Oracle middleware.
Programs that open DAD files
Windows2 apps
Thermo Scientific Dionex Chromeleon CDS
Paid Open the run/channel inside Chromeleon (the CDS that created it) to view, reprocess and report the data.
Chromeleon data export (to CDF/CSV/PDF)
Paid Within Chromeleon, export the channel/results to AIA-CDF (.cdf), CSV or a PDF report so other tools or reviewers can use the data. Technical details
deep spec| Encoding | Binary, proprietary little-endian |
| Byte order | Little-endian |
| MIME type | application/octet-stream |
| Magic bytes | None publicly documented; file is identified by its Chromeleon datasource context, not a fixed byte signature |
| Signal content | Raw absorbance intensity time-series from a Diode-Array Detector (DAD) UV/Vis channel |
| Container context | Stored inside a Chromeleon datasource or sequence folder, not a self-contained standalone archive |
| Companion files | `.seq` (sequence), `.qnt` (quantitation), `.cmbx` (metadata) within the same datasource folder |
| Typical file size | Tens of KB to a few MB per channel, depending on sampling rate and run length |
| Detector sampling rate | Acquisition rate in Hz configured per Chromeleon instrument method; determines data density |
| Format versioning | Tied to Chromeleon CDS version (6.x or 7.x); internal version not publicly specified |
| Encryption | None by default; access control enforced at Chromeleon datasource level |
| Data integrity | Audit-trail and integrity checks managed by Chromeleon CDS for 21 CFR Part 11 compliance; not embedded in the file itself |
| Associated OS | Windows only |
| Export capability | Data exportable to CDF, CSV, or PDF via Chromeleon's built-in export tools |
| Superseded by | Chromeleon 7.x managed repository (eWorkflows/sequences) reduces reliance on loose channel files |
| Released | Dionex Chromeleon CDS (1990s-2000s) |
| Latest version | Tied to the Chromeleon Chromatography Data System version that wrote it |
| Specification | www.thermofisher.com |
DAD conversions
Community Q&A
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