Frame trace: every CAN frame in time order
Each frame shows its time, channel, ID, DLC, direction (Rx or Tx) and data bytes. Channels are detected from the BLF file, and each channel keeps its own colour.
Online BLF viewer for Vector CAN and CAN FD log files
This BLF viewer lists every CAN and CAN FD frame in a .blf file and decodes signals with your DBC. Nothing is uploaded.
Drop a BLF file to view it
orAny Vector BLF with CAN or CAN FD frames. Link a DBC to each channel next, or skip it and look at the raw frames.
What the BLF viewer shows in a BLF file
BLF is a compressed binary format, so a text editor cannot display it. The BLF viewer decompresses the log containers and lists the frames in time order, like a CAN trace.
Frame filters: find an ID, channel or byte pattern
Filter by time range, ID or ID range, channel, frame type or a byte pattern with ?? wildcards, or type a query such as id:100-1FF ch:1 t:2..4.
Frame details: flags, signals and bit activity
Expand a frame to see its flags (FD, BRS, ESI, error), its decoded signals and which bits change across the log. J1939 traffic gets a PGN column.
Signal plots: decode the BLF with a DBC
Link a DBC to each channel and plot any decoded signal over time, with two cursors to read values and the time between them.
How to view a BLF file online
Three steps in the BLF viewer. The file never leaves your browser.
Open the BLF file
Drop the .blf file on this page or choose Open a BLF file. The BLF viewer reads it locally and detects its CAN channels.
Link a DBC to each channel
Add the DBC for each bus to decode signal names and physical values. Skip this step to view the raw frames only.
View frames and plot signals
With a DBC the BLF opens on the signal plots; without one it opens on the frame trace. Filter frames, expand any frame, or measure with two cursors.
Supported BLF file contents
The BLF viewer reads CAN, CAN FD and error frames. These are the BLF objects it supports and the ones it skips.
- CAN frames with standard (11-bit) and extended (29-bit) IDs
- CAN FD frames, including 64-byte payloads and the BRS and ESI flags
- Error frames, shown as their own rows
- Compressed and uncompressed log containers, as written by CANoe and CANalyzer
- Several channels in one file, and files up to 150 MiB
- LIN, FlexRay and Ethernet objects are skipped.
- A Windows .blf (Common Log File System) is a different format and will not open.
When to use an online BLF viewer
Typical reasons to view a BLF file in the browser instead of opening it in CANoe or CANalyzer.
View BLF files without a Vector licence
CANoe and CANalyzer run on Windows and need a licence. A test log someone sends you can be checked on any laptop, Mac and Linux included.
Keep confidential BLF logs on your computer
Many free online viewers upload the file to a server. Here the BLF is read inside your browser tab, so it never leaves your computer.
Check a BLF file a script cannot read
Script readers can stop on CAN FD or newer BLF objects. A quick look shows whether the frames are there before you debug the code.
Triage a BLF log before full analysis
Check that an ID appears, on which channel, how often and whether error frames show up, before you set up a full measurement.
Other tools for BLF files
Use the BLF viewer to inspect a log. For other jobs with a BLF file, these pages fit better.
Convert BLF to MAT or CSV
For MATLAB, Simulink or pandas: decode with your DBC and download one file per log.
Open a BLF file without CANoe: step-by-step guide
Four ways to open a BLF without CANoe, including Python with python-can and cantools.
Inspect the DBC used to decode the BLF
Check a signal's start bit, scaling and value table before you decode the BLF.
BLF viewer FAQ
Is my .blf file a CAN log or a Windows log?
Both use the .blf extension. A Vector BLF from CANoe or CANalyzer holds CAN bus frames and opens here. A Windows Common Log File System .blf is a system log, which is a different format.
What can I see in a BLF before I have the DBC?
Time, channel, ID, DLC, direction and data bytes for every frame, plus how often each ID repeats and which bits change. Signal names and physical values need the DBC.
Which BLF object types does the BLF viewer read?
CAN messages, CAN FD messages up to 64 bytes and error frames, from compressed or uncompressed log containers. LIN, FlexRay and Ethernet objects are skipped.
How do I find one CAN ID in a long BLF file?
Open the filter, enter the ID in hex or a range such as 100-1FF, and choose Only these. You can combine it with a channel, a time range and a byte pattern.
Does it show CAN FD flags and error frames?
Yes. Expand a frame to see the FD, BRS and ESI flags. Error frames are listed as their own rows and marked as errors.
My BLF has several channels. How are they shown?
Each frame shows its channel number and every channel has its own colour. You can filter to one channel and link a different DBC to each one.
Can I try the BLF viewer without my own BLF file?
Yes. Open the synthetic sample BLF. It opens with its public opendbc DBC already linked, so speed, steering angle and pedal position are decoded and plotted straight away. It is not a real vehicle recording.
View your BLF file now
It runs in your browser. Nothing to install, and the file stays on your computer.
More free tools
The next job after this one, each on its own page.