What is the MF4 file format?
.mf4 is the file extension for ASAM MDF 4 (Measurement Data Format version 4), the automotive industry's open standard for storing time-series measurement data from ECUs, CAN/LIN/Ethernet buses, and sensors. The standard is maintained by ASAM e.V. and was co-developed by Vector Informatik and Robert Bosch GmbH.
Each .mf4 file opens with a 64-byte ID block bearing the ASCII identifier MDF (8 bytes with trailing spaces), followed by a hierarchical linked-list of typed blocks: Header (HD), Data Groups (DG), Channel Groups (CG), Channel definitions (CN), and Data blocks (DT/DZ). Every channel carries its signal name, physical unit, and value conversion formula in the same file, making .mf4 self-describing.
Data compression - DEFLATE, LZ4, or Transpose+DEFLATE - can be applied per data block since MDF 4.1. The format supports attachment blocks for embedding calibration files or images, and a finalization flag marks whether a recording was cleanly closed. Unfinalized recordings begin with the ASCII string UnFinalizedMDF instead of the standard ID block.
.mf4 is used throughout HIL/SIL testing, vehicle data acquisition, and AUTOSAR calibration workflows. Files can reach tens of gigabytes for full test-drive sessions. The open-source Python library asammdf (pip install asammdf) provides fast read/write access; MATLAB, CANape, and CANalyzer are the dominant commercial tools. The predecessor .mdf format (MDF 3.x, from 1991) shares the same file-identifier prefix but uses a different block structure.
Security & safety
RISK: LOWMF4 is a binary data file; not executable. Files may contain proprietary automotive measurement data (vehicle signals, ECU parameters) that is commercially sensitive. Sharing .mf4 files externally may expose confidential calibration or performance data.
Format details
in a nutshellFULL NAMEASAM MDF Version 4 Measurement Data Fileaka MDF4, MDF 4
DEVELOPERASAM e.V. (Association for Standardization of Automation and Measuring Systems); originally co-developed by Vector Informatik GmbH and Robert Bosch GmbHsince 2009 (ASAM MDF 4.0 published as official standard)
CATEGORYData Files
MIME TYPEapplication/octet-stream
TYPEbinary time-series measurement data (automotive/embedded)
STANDARDOpen · royalty-free
MAGIC BYTES · FILE SIGNATURE
OFFSET
0001020304050607
HEX
4D44462020202020
ASCII
MDF
64-byte ID block at start of file; bytes 0-7 contain file type identifier. MDF 3.x uses the same prefix. Version info at offset 8 (4 chars, e.g. '4.10'). Unfinalized MDF4 files begin with 'UnFinalizedMDF' (55 6E 46 69 6E 61 6C 69 7A 65 64 4D 44 46).
Programs that open MF4 files
Windows6 apps
vSignalyzer (formerly CANgraph)
Paid Open .mf4 for signal visualization and analysis; formerly called CANgraph.
MATLAB (with ASAM MDF DataPlugin or Vehicle Network Toolbox)
Paid Use mdfDatastore() or the ASAM MDF DataPlugin to import .mf4 signal data into MATLAB workspace.
asammdf (Python library)
Open-source pip install asammdf; MDF4(filename).to_dataframe() to load into pandas. Includes a GUI (asammdf GUI) for no-code signal browsing.
MDF Validator (Vector, free)
Free Validates .mf4 file conformance to ASAM spec; useful for checking files before processing. 
Linux1 app
asammdf (Python library)
Open-source pip install asammdf; full read/write support for MDF 4.x and 3.x. Technical details
deep spec| Standard body | ASAM e.V. (Association for Standardization of Automation and Measuring Systems) |
| File identifier | 8-byte ASCII 'MDF ' (MDF + 5 spaces) at offset 0 of the 64-byte ID block |
| Byte order | Little-endian (default); big-endian allowed by spec but rarely used |
| Block structure | Hierarchical linked-list: ID → HD → DG → CG/CN → DT/DZ blocks via absolute byte-position pointers |
| Compression | Optional DEFLATE (zlib), LZ4, or Transpose+DEFLATE per data block (MDF 4.1+) |
| Typical file size | 1 MB - 10 GB (large ECU/CAN log sessions) |
| Signal metadata | Signal name, physical unit, and value conversion formula stored per channel within the file |
| Version encoding | 4-character ASCII string at ID block offset 8 (e.g., '4.10', '4.20') |
| Bus logging support | CAN, LIN, FlexRay, and Ethernet frame logging (added in MDF 4.1+) |
| Integrity checking | Optional MD5 checksum attachment; finalization flag in MDF 4.1+; unfinalized files start with 'UnFinalizedMDF' |
| Python access | asammdf library (pip install asammdf) - open-source read/write |
| Sample rate | Per-channel metadata; CAN bus typically 1-1 000 Hz, sensor data up to MHz range |
| Operating systems | Windows, Linux |
| Released | 2009 (ASAM MDF 4.0 published as official standard) |
| Latest version | ASAM MDF 4.2.0 (2019); 4.3.0 planned |
| Open standard | Yes · royalty-free |
| Specification | www.asam.net |
MF4 conversions
Community Q&A
asked by users
A
Frequently asked questions
What is an .mf4 file?
An ASAM MDF 4 measurement data file - the automotive industry standard binary format for storing time-series ECU, CAN bus, and sensor data.
How do I open an .mf4 file for free?
Use the open-source Python library asammdf (pip install asammdf). It includes a GUI (run 'asammdf' after install) for browsing signals without coding. Vector's free MDF Validator can also check file integrity.
Can MATLAB open .mf4 files?
Yes - with the Vehicle Network Toolbox (mdfDatastore function) or the free ASAM e.V. DataPlugin for MDF4 from NI/MATLAB ecosystem.
How do I convert .mf4 to CSV?
Using asammdf:
from asammdf import MDF; MDF('file.mf4').export('csv'). Or open in CANape and use its export function.What is the difference between .mdf and .mf4?
.mdf is the older MDF 3.x format; .mf4 is explicitly MDF 4.x. Both use the same magic bytes but differ in version string. asammdf and Vector tools read both.
Is ASAM MDF 4 an open standard?
Yes - published and maintained by ASAM e.V. The specification is available from asam.net (registration required for full PDF).
References
1ASAM MDF Standard pagewww.asam.net
2Vector - MDF format overviewwww.vector.com
