Choosing an Online CAN Log Viewer for BLF, MF4 and DBC

Canmetry is a browser workbench for recorded CAN and CAN FD logs. It opens BLF, MF4, ASC, CSV and candump .log files, shows raw frames, and uses a matching DBC to decode signals. Choose it when you need to inspect an existing recording; check your file and DBC with the workbench before relying on a result.

The decision starts with your desired output. A frame check needs the recording alone. A physical value needs a DBC from the recorded network. A MATLAB handoff needs decoded signals in a format the receiving script expects. These are different jobs, even when they start with the same BLF or MF4 file.

Choose by the job

Your job	Canmetry path	Check before you commit
Find an ID, channel or changing payload	Open the log in the workbench and inspect raw frames	A DBC is optional for raw frames; confirm your file variant opens.
Plot named physical signals	Map each channel to a matching DBC, then use the Signals view	Wrong DBC versions or channel mappings can produce missing or incorrect values.
Deliver decoded data to another tool	Use BLF to MAT/CSV, MF4 to MAT/CSV or ASC to MAT/CSV	These export decoded results; confirm the destination format and each tool’s limits.
Reopen settings or share files	Sign in and choose a cloud project or explicit cloud file upload	Saving settings sends metadata; uploading log or DBC bytes is a separate choice. Check current plan availability on Pricing.
Capture live traffic, transmit frames or run HIL tests	Use equipment and software built for live bus work	This browser workbench starts with a recorded file.

Find out what was recorded

Start in the Frames view when the immediate question is whether an ID appeared, which channel carried it, or whether payload bytes changed near an event. You can do this without a DBC. Note the timestamp, channel, frame type, ID and payload before assigning any signal meaning to the bytes.

Turn frames into physical signals

A DBC describes how a message's bits become named values: byte order, signedness, scale, offset and units. It does not come from the log automatically. If a supplier sends a BLF from two CAN channels, ask which DBC and software revision belongs to each channel. A plausible-looking speed trace is not proof that the mapping is correct; check a known frame ID and one raw value against the DBC before using a plot in a report.

Hand results to another tool

Use the workbench's signal CSV when you need selected decoded signals for a quick check. Use the BLF, MF4 or ASC converter when the deliverable is a separate MAT or CSV file. Those outputs contain interpreted signal samples; they are not a lossless copy of every original frame. If you need raw bytes for later decoding, keep the source log and choose a raw-frame export workflow such as BLF to CSV.

Canmetry at a glance

Question	Current browser workflow
Which recordings?	The workbench has readers for BLF, MF4 CAN bus logging groups, ASC, CSV and candump .log. An MF4 file can contain other measurement layouts that this reader does not handle.
CAN FD?	Supported where the selected input contains CAN FD frames.
Need a DBC?	No for raw frames. A matching DBC and correct channel mapping are needed for named signal values and plots.
File size?	The local workbench and the BLF/MF4/ASC converters accept up to 150 MiB per log file. Browser memory and MF4 decompression limits may matter before that size.
What can I export?	Signal CSV from the workbench; separate conversion pages produce MAT or CSV. Use the tool page for its exact output and row limits.
Where are files processed?	Opening a local file parses it in your browser without uploading its bytes. Cloud projects send settings and metadata; cloud file upload and the AI assistant are optional actions with separate data flows. See the Privacy Policy.
Is it free?	Local analysis is free. Pro and Team availability depends on the current checkout configuration; the Pricing page shows the current state.

Check the input before choosing the workflow

The extension alone is not enough to establish compatibility. An MF4 container can hold measurement data other than CAN bus logging groups. CSV layouts vary by exporter. Open one representative recording and confirm that the expected channels, timestamps and frame counts appear. For an MF4-specific walkthrough and its known exclusions, see the MF4 viewer; for BLF objects, see the BLF viewer.

Keep file size and data location separate

The 150 MiB limit applies to each local log in the workbench and the listed signal converters. Near that size, available memory and the file's internal structure also affect whether processing completes. A cloud upload allowance, if available on a paid plan, does not raise the local decoding limit. Opening a file locally sends no log or DBC bytes for parsing; saving a cloud project sends settings and metadata, while cloud file storage requires a separate file choice. The privacy policy lists what the AI assistant sends when you use it.

Try your own file in three steps

1. Learn the views with a sample

Open the built-in sample to see the Frames and Signals views without preparing a file. The sample includes a matching demo DBC, so signal names appear; your own log will need its own DBC for that result.

2. Verify the raw recording

Open your own log locally. Check timestamps, channels and IDs in Frames first. If your MF4 is not a CAN bus logging file or uses an unsupported layout, the reader may reject it.

3. Verify one decoded value

Add the DBC from the recorded network and software version, map it to the right channel, then inspect a known signal. Check the raw bytes and scaling when a value looks surprising. Export only after that check.

For example, if a DBC defines a 16-bit unsigned little-endian speed signal with factor 0.01 and offset 0, raw bytes 9D 09 give integer 0x099D (2461) and therefore 24.61 in the DBC's unit. This is an illustration of the check, not a rule for arbitrary vehicle signals: use the actual bit position, endianness, factor and offset from your DBC. If only some signals appear, inspect the channel mapping and whether the DBC contains each message ID before concluding the log is incomplete.

When another workflow fits better

Live measurement and automated tests

Canmetry currently does not connect to a CAN interface to capture traffic or transmit frames, and it does not run ECU simulation, CAPL or HIL tests. Vector describes CANoe as covering analysis, simulation, testing and diagnostics; compare its edition and options with your live hardware requirements.

Repeatable batches and large recordings

If you must process hundreds of files the same way, write down the DBC version, channel mapping, filters and output schema and automate the run. A one-file browser check is useful for establishing those rules, but it is not a batch pipeline. For an oversized ASC, the ASC splitter can trim a time window or split by duration or size before import. Check that each part retains the event and timestamp range you need; splitting does not create a matching DBC.

For repeated BLF processing, a script using python-can and cantools can make the mapping and output rules explicit. Keep a small known log as a check when you change those rules.

Frequently asked questions

Can I open a BLF without CANoe?

Yes, for a supported recorded BLF. Start with the BLF viewer or follow the four ways to open a BLF without CANoe.

Does an MF4 require a DBC?

You can inspect supported raw CAN frames without one. To see named physical signals, map a DBC that matches the recorded bus. The MF4 viewer explains which CAN logging files fit; the reader does not handle every MDF4 measurement layout.

Does opening a log upload it?

Opening it in the local workbench does not upload the file bytes. Saving a cloud project sends settings and metadata. Uploading a log or DBC to cloud storage requires a separate selection; using the AI assistant sends your message and signal catalog context to the service and AI provider.

Is local analysis free?

Yes. See Pricing for current paid plan and checkout availability.

Can I connect a live CAN interface?

No. This workbench analyzes recordings. For the difference between offline analysis and live CANoe tasks, read the CANoe alternative guide.