FIT File Merger — Combine FIT Files Free, Offline
Drop the FIT files from your head unit, watch and power meter into TrailBlender and get one clean activity back, with every sensor channel intact. Nothing is uploaded: the merge runs on your own computer.
No upload · No account · Works without an internet connection
Merge FIT files in three steps
- 01
Drop in your FIT files
Drag the recordings from your Garmin, Wahoo, Coros or Hammerhead straight into TrailBlender. Two files or ten, FIT or GPX, mixed is fine.
- 02
Pick the best source for each channel
TrailBlender lines the files up by timestamp, shows the overlap on the map, and lets you choose which device supplies GPS, power, heart rate and cadence.
- 03
Export one file and upload
Save the merged activity as FIT (or GPX) and upload it to Strava, Garmin Connect, TrainingPeaks or intervals.icu like any other ride.
Ready to merge your FIT files?
Download TrailBlender, drop in your files and export a single clean activity in under a minute.
Works with the devices you already ride with
Any device that writes a standard FIT file is supported. That covers:
Garmin
Edge, Fenix, Forerunner and Venu files, downloaded from Garmin Connect or copied over USB.
Wahoo
ELEMNT BOLT, ROAM and ACE recordings from the ELEMNT app or the device's Activities folder.
Coros
PACE, APEX and VERTIX workouts exported as FIT from the COROS app.
Hammerhead
Karoo 2 and Karoo 3 rides exported from the Hammerhead dashboard.
Apple Watch
Workouts exported with HealthFit, RunGap or WorkOutDoors; the Watch has no built-in FIT or GPX export.
Suunto, Polar, Bryton and Stages files work too. If your device produces a FIT file, TrailBlender can read it.
Your ride data stays on your computer
TrailBlender is a desktop application, not a web service. Your FIT files are read from disk, merged in memory and written back to disk. There is no upload step and no account to create.
That also means the merger keeps working on a train, in a hotel lobby or at a campsite with no signal. Once the app is installed, an internet connection is never required.
FIT merger questions
Does the merged file keep power, heart rate and cadence?
Yes. TrailBlender reads every record in each FIT file and lets you choose which device supplies each channel, so power from your head unit and heart rate from your watch end up in the same file. Garmin-specific fields such as Training Effect are carried over from the primary device.
Is there a maximum file size?
No hard limit. Because the merge runs on your own machine rather than in a browser tab, a 12-hour ride recorded at one-second intervals (often 20 to 40 MB per file) merges without trouble. Very large batches are limited only by your computer's memory.
Does Strava accept merged FIT files?
Yes. Export the result as FIT or GPX and upload it through Strava's upload page or the mobile app; Strava treats it as a normal activity. Delete the partial recordings first so Strava does not flag the merged ride as a duplicate.
Does it run on Mac, Windows and Linux?
It does. TrailBlender ships as a macOS app for Apple silicon and Intel Macs, a Windows installer and a Linux AppImage. The merger behaves the same on all three.
Can I merge a FIT file with a GPX file?
Yes. Mixed formats are common when one recording comes from a watch that only exports GPX. TrailBlender aligns both by time and exports the combined activity in whichever format you choose.
Is the FIT File Merger really free?
Yes. The current version of TrailBlender is free to download and use, with no account, trial period or watermark on the exported file.
Step-by-step guides for common merges
Need a walkthrough for a specific situation? These guides cover the merges riders ask about most.
How to Merge FIT Files from Garmin, Wahoo & Coros
Merge multiple FIT files into one activity. Combine Garmin, Wahoo, and Coros recordings with all sensor data preserved — free with TrailBlender.
How to Combine Power and Heart Rate Data from Two Devices
Merge power meter data from your head unit with heart rate from your watch into one file. Get complete training data in a single Strava activity.
How to Merge Wahoo and Garmin Ride Data
Combine Wahoo ELEMNT and Garmin Edge ride data into one activity. Merge sensor channels from both devices for a complete Strava upload.
Garmin Died Mid-Ride? How to Recover and Merge Your Data
Your Garmin battery died mid-ride and you finished on your phone. Learn how to merge both recordings into one complete activity for Strava.