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THE FILE FIELD GUIDE
.fit

FIT Activity or Other Data

Maps & GPS

FIT is a binary format used for activities/sensors by Garmin and others, potentially including time, GPS and heart rate. Astronomy FITS also uses .fit; establish the producer. This guide focuses on activity FIT.

Main use
Device-recorded activities and sensor data
Data type
Multiple uses; identify the producer
All sections, questions and sources

Content reviewed： · Editor：Kai

Opening steps

Choose your environment or purpose to see its steps.

Garmin FIT SDK / activity-compatible software

Preserve the original and inspect a working copy in a compatible application.

  1. Confirm that it came from an activity-recording device/app.
  2. Import a copy into compatible activity software or inspect it using FIT SDK tools.
  3. Inspect timestamps, activity type, distance and required sensor fields.
Inspect the received file and its requirements

Establish dependencies and settings before proceeding.

  1. Identify device, recording content and displayed timezone.
  2. Distinguish outdoor GPS from indoor sensor activity.
  3. Establish sharing scope for location/health-related data.

Menu labels and support vary by app, OS and version. Preserve the original before making changes.

Troubleshooting by symptom

  • No map: check whether GPS was recorded, such as for an indoor activity.
  • No heart rate: inspect sensor recording and importer support.
  • Times differ: inspect stored time and display timezone.
  • Not recognized as activity: inspect astronomy FIT or another use and corruption.

FIT → TCX / GPX / inspection CSV

  1. Use activity export or FIT CSV Tool, selecting a format that retains required fields.
  2. Verify duration, distance, laps, required sensors and location visibility.

GPX and other exports may not preserve heart rate, laps and device-specific fields equivalently.

Activities versus routes

A GPS route may not represent indoor/sensor-centered activity. Choose the format after identifying whether location, laps, heart rate or other fields matter.

Source for these steps：Garmin · FIT SDK overview / Garmin · FIT CSV Tool / Garmin · Empty TCX/GPX activity export

Worked example: checks before handoff

Example: for indoor training, absence of a GPX map does not imply corruption; inspect time/laps/sensors in original FIT or supported TCX.

Source for these steps：Garmin · FIT SDK overview / Garmin · FIT CSV Tool / Garmin · Empty TCX/GPX activity export

Related-format differences

Related-format differences
Format / methodPurpose and preserved information
.fitDevice-recorded activities and sensor data
TCX / GPXTCX is activity/course XML and GPX mainly GPS data, with different fields.
FIT → TCX / GPX / inspection CSVGPX and other exports may not preserve heart rate, laps and device-specific fields equivalently.

Handling and security

Files may reveal home-area locations, routes and health-related data; review scope before publication.

Questions and answers

Will an activity tool read astronomy FIT?

No equivalence is implied; use the FITS guide for astronomy data.

Will GPX preserve everything?

It is mainly location/route-oriented; inspect activity/device-specific preservation.

Is a mapless FIT corrupt?

Indoor records may lack GPS; inspect activity and sensor content.

Format facts: name, steward and MIME type
Formal name
FIT Activity or Other Data
Steward / specification
Garmin
MIME type
Consult the producer or delivery system. The extension alone does not establish a MIME type.

Primary and official sources

  • Software documentationFIT SDK overview

    FIT records, messages and SDK tooling.

    Garmin · Link checked：
  • Software documentationFIT CSV Tool

    Tool for inspecting/converting FIT and CSV.

    Garmin · Link checked：
  • Software documentationEmpty TCX/GPX activity export

    Export limitations for long/indoor activities and original FIT files.

    Garmin · Link checked：