What is FitMerge?
FitMerge joins the pieces of one outing into a single activity file. The watch died and you finished on your phone, you pressed Save instead of Pause, or the app crashed and the run is in two files: drop the FIT, GPX or TCX files in and download one file to upload to Strava or Garmin Connect.
Strava can't join two activities itself. You export each part from strava.com, merge them here, delete the parts on Strava and upload the merged file. Reading, merging and writing all happen in your browser, and there's no account and no Strava login.
Key Features
Two to ten files, in any order
FitMerge sorts the parts by start time. Files can be up to 100 MB each, zip and gz archives go in unopened, and you can mix formats, say a FIT from the bike computer and a GPX from the phone.
The gap becomes a pause
The time between parts counts as a pause, so moving time and averages come from the recorded parts only and cumulative distance carries on. A gap over 2 hours asks you to confirm; parts more than 12 hours apart aren't merged. An option adds the climb or drop across the gap, and the page warns when the second part starts more than 1 km from where the first ended.
What carries over
Laps, heart rate, power, cadence, temperature and the GPS track come through, and a part with no laps becomes one lap. The merged FIT keeps the maker and model of the device that recorded it, so Strava and Garmin Connect treat the result like a normal activity, and Strava keeps the recorded elevation when it knows the device has a barometric altimeter. Distance, time, averages and maximums are worked out again for the whole activity.
Check before you download
A map shows each part in its own colour, and a before-and-after table gives distance, moving time, elevation, heart rate and power for each part and for the merged activity.
Files that went wrong
A file cut off by a dead battery is read up to the break and merged, with a warning. A part that never recorded its sport takes the other part's; if the parts disagree, you pick one before downloading.
What goes to Strava
Nothing directly. FitMerge has no Strava connection: you download the merged file and upload it on strava.com yourself. FIT is the default download and the one to choose for Strava, since it keeps the device, the sport, the laps and the pauses. Delete the original parts first, or Strava may turn the upload away as a duplicate, and your totals would count the outing twice.
Who It's For
- Anyone whose watch or bike computer died mid-activity and who finished on a phone
- People who saved or finished by mistake and started a second recording to carry on
- Runners, riders and hikers with a crash or reboot that left one outing in two files
- Anyone who'd rather not upload their files to a website to merge them
What it doesn't do
It won't merge files that overlap in time, such as a watch and a phone recording the same stretch; it names both files and refuses the pair. It can't trim a file either, so overlapping minutes have to come off one part first.
It joins recordings, not planned routes: a GPX with no times is turned away. Swims and triathlon files aren't supported.
A GPX download has no laps, pauses or calories, and a TCX can only say running, biking or other, so download FIT for a hike, a walk or any other sport. Data fields added by Connect IQ apps are left out, with a note on the file that had them.
Do I lose my kudos and comments?
Yes, and the photos go with them. They belong to the activities you delete, and Strava can't move them to the merged one. Copy the title and description before you delete, and check the photos are still on your phone so you can add them back.
Can I do it on a phone?
Yes, in the phone's browser. The Strava app can't export or upload a file, so open strava.com in the browser to export each part (switch to the desktop site if the export option is missing), merge them on FitMerge, then upload the merged file at strava.com.
What leaves my browser?
Not your files. The map loads its tiles from OpenStreetMap, the site counts page views with Cloudflare Web Analytics, and the page sends short usage counts such as "merged 3 files" to FitMerge's own server, which adds the country and whether it was a phone, with no file contents, file names, locations or activity times. There are no cookies and no sign-in.
