---
id: fitdecode
version: "0.11.0"
license: MIT
license_treatment: permissive
maintenance: aging
---

# fitdecode — FIT file parser and decoder

License: permissive · Maintenance: aging · Downloads: 103.8K/mo

## What it is and what it does

fitdecode is a Python library for reading and decoding FIT files—the binary format used by Garmin devices and ANT+ sensors to store fitness and activity data. It provides frame-by-frame parsing via a FitReader context manager, yielding typed objects (headers, definition messages, data messages, CRC footers) that preserve the complete structure of the input file. The library also includes command-line utilities (fitjson and fittxt) to convert FIT files to JSON or text format for inspection and debugging.

Unlike its predecessor fitparse, fitdecode prioritizes thread-safety, speed, and memory efficiency. It retains FIT headers and CRC footers in the output, supports optional CRC validation, and can handle chained (concatenated) FIT files. It also offers binary-level access to records for advanced use cases like file cutting and stitching. The package has no runtime dependencies and installs as a pure Python wheel.

Use it for:

- Extract workout metrics (distance, heart rate, cadence) from Garmin device FIT files for analysis or logging.
- Convert FIT files to JSON for integration with web services or data pipelines.
- Debug malformed or non-standard FIT files using human-readable text output.
- Process multiple FIT streams concurrently in a multi-threaded application.
- Validate FIT file integrity and structure before downstream processing.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Parses and decodes FIT files (Garmin's ANT+ fitness data format) into Python objects, with command-line tools to convert FIT to JSON or human-readable text.

Yes, if you need to parse Garmin FIT files. The package is mature (Beta status since 2018), has no dependencies, installs easily, and covers current Python versions. Maintenance is aging (373 days since last release), but the repository is active and recent updates addressed SDK profile upgrades and edge cases. No known security vulnerabilities. The only caveat is that if you need cutting-edge FIT SDK features, verify that v21.171.0 covers your use case.

## Install

pip install fitdecode
uv add fitdecode
poetry add fitdecode

## Installing fitdecode

Before you install: Low friction: pure Python wheel with no runtime dependencies. Maintenance status is aging—last release was 373 days ago—but the repository remains active and the package supports current Python versions (3.6 through 3.13).

License in practice: MIT license is permissive; you can use, modify, and distribute this package freely in commercial and private projects without restriction.

Quickstart:

import fitdecode

with fitdecode.FitReader('file.fit') as fit:
    for frame in fit:
        if frame.frame_type == fitdecode.FIT_FRAME_DATA:
            print(frame.name)

Requires Python >= 3.6; FIT file must be a valid Garmin FIT format file.

Verify before relying:

- Whether thread-safety guarantees hold across all concurrent access patterns in production use.
- Performance characteristics (speed and memory usage improvements over fitparse) under typical workloads.
- Completeness of FIT SDK profile v21.171.0 coverage for all Garmin device types.

## Package facts

- License: MIT (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: aging
- Downloads: 103.8K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

fit file parser, garmin fit decoder, ant+ data parsing, fitness file format, fit to json conversion, garmin data extraction, fit file reader, fitness-data, garmin, file-parsing

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