01
Identify the file
See whether the FIT file contains an activity, workout, course, settings, wellness data, or another FIT data type, plus its device and creation metadata.
Free local file tool
FIT File Viewer
Open a FIT file locally without uploading it. Inspect activity summaries, a 3D route, Record charts, CRC checks, and decoded messages—nothing leaves this device.
LOCAL FIT INSPECTION
- Header
- CRC
- Messages
Local only · no network
Choose a FIT file
One .fit file, up to 25 MB. Nothing is uploaded.
Choose .FIT fileor drag it here
One .fit file, up to 25 MB. Nothing is uploaded.What does a FIT File Viewer show?
A FIT File Viewer decodes the binary Flexible and Interoperable Data Transfer format used by Garmin and other fitness devices. This viewer exposes the file header, identity, summary, 3D route, Record charts, integrity checks, and decoded message groups.
02
Check integrity
Validate the .FIT signature, expected file size, header CRC when present, and file CRC using Garmin's official JavaScript SDK.
03
Visualize and inspect the data
Explore the route in 3D, switch between Record metrics, and browse records, sessions, laps, events, developer fields, and other decoded message groups.
How to open a FIT file
- 01
Choose the .fit file
Select one FIT file from your computer or drag it into the viewer. Files are limited to 25 MB.
- 02
Inspect the results
Review file identity, activity-level values, the 3D route, Record charts, CRC status, decoder warnings, and available FIT messages.
- 03
Export what you need
Download all decoded data as JSON or one message group as CSV. The export is created locally without a network connection.
FIT File Viewer FAQ
How do I open a FIT file?
Choose a .fit file or drag it into this FIT file viewer. The file opens locally in your browser—nothing is uploaded. You can then inspect the activity summary, 3D route, Record charts, CRC checks, and FIT messages.
What is a FIT file?
FIT stands for Flexible and Interoperable Data Transfer. It is a compact binary format used by Garmin and many fitness devices for activities, workouts, courses, health data, settings, and other sports data.
Is my FIT file uploaded?
No. The file is read entirely on your device. It is not uploaded, and Trainingload.ai never receives the file bytes or decoded contents.
Is a FIT file reader the same as a FIT file viewer?
Yes. Both names describe this local tool: it opens a FIT file in your browser so you can read messages and summaries. It does not convert or upload the file.
Which FIT files can this viewer open?
It can inspect standard FIT files recognized by the official Garmin FIT JavaScript SDK, including activity, workout, course, wellness, and device-related files up to 25 MB.
What does a failed CRC check mean?
It means the file signature, declared size, header CRC, or file CRC did not pass Garmin SDK integrity checks. The file may be incomplete, corrupted, or exported in a non-standard way; partial messages may still be readable.
Can I view FIT developer fields?
Yes. The decoder includes recognized developer-defined fields and reports how many developer field descriptions were encountered.
Based on the official FIT SDK
File decoding and CRC validation use Garmin's official FIT JavaScript SDK. You can review its source code on GitHub or read Garmin's FIT developer documentation.
Last updated: September 6, 2026
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