FitMerge

Guide

Merge two Zwift rides into one

The app froze, the connection dropped or you had to close Zwift halfway, and one session became two activities. Put both .fit files in the tool below to make them one ride again.

  1. Add files
  2. Check
  3. Download

Need the files? How to export them from Strava, Garmin Connect, Wahoo and more

From two Zwift files to one ride

  1. Download a .fit for each part. On zwift.com, go to your feed, pick JUST ME, open the activity, click the cog icon and choose DOWNLOAD FIT FILE. Do it once for the part before the trouble and once for the part after.
  2. Or take them from the computer you rode on. Zwift writes each activity file while you ride. On a Mac they are in Documents/Zwift/Activities. On Windows, rides since February 2026 are under AppData\Local\Zwift\Activities in your user folder, and older ones stayed in Documents\Zwift\Activities. On a phone or tablet, the grey file icon on Zwift's title screen lets you email the files to yourself.
  3. Drag both into the box above. FitMerge puts them in time order, shows each one on its own row and adds up the whole session.
  4. Download the result. FIT is chosen for you, as the format that keeps the most of a ride. Then swap the two parts for the new file where your rides live, as described further down.

Both files are opened by this browser tab on your own computer or phone. Neither one is uploaded to us.

How a single session splits in two

A crash or a lost connection. In a thread on Zwift's forum, a rider who lost his network restarted the app, carried on from the same place and found two activities afterwards. The reply from Zwift's technical support team said this sometimes follows a Wi-Fi or internet problem or an app crash, and that closing and reopening the app can leave several .fit files for what was one ride.

A warm-up kept on its own. Some riders save the spin before a race or group ride as one activity and ride the event as another. If you would rather see the evening as one effort, merge the two.

A restart you chose. A trainer that stopped responding or a heart rate strap that wouldn't pair can be reason enough to quit Zwift and start again. Whatever the cause, the result is a ride before and a ride after.

Why Zwift can't join them

Zwift's article on your activities covers renaming a ride, changing who can see it and deleting it in the Companion app. There is nothing in it about putting two together. The support reply in the forum thread pointed the other way: merge the .fit files with a third-party tool, then upload the combined file to Strava by hand. This page is one such tool, and nothing is installed to use it.

What survives the merge

  • Every second of data. Power, heart rate and cadence samples from both files end up in the merged one. We check it on a real Zwift race file split in the middle: the counts after the merge equal those of the two halves added together.
  • The virtual route. The Zwift file we test with has a map position on every point, so the map draws the course and GPX is on offer too. Files from an indoor app that writes no positions still merge; GPX is then greyed out.
  • The right start time. The Zwift file we test with stores 0 in the field where a FIT keeps local time, which can't be a real time zone. FitMerge leaves that value out and shows times in your browser's time zone instead.

The summary of distance, moving time and averages is calculated afresh for the whole session. The minutes you spent restarting are a pause, not riding.

For laps, devices and what else a FIT carries, see the FIT guide.

Putting the merged ride on Strava or Garmin Connect

Once Zwift is linked to Strava, Strava's help explains that rides sync on their own, so both halves are probably there already. Zwift's support team suggested deleting the Strava copy first and only then uploading the merged .fit. The Strava guide and the Garmin Connect guide go through removing the parts and adding the new ride, and the upload guide lists other sites.

Questions

Zwift recovered my ride, and the two files cover the same minutes. Why won't they merge?

Joining them would count those minutes twice, so FitMerge stops and names both files as an overlap rather than forcing them together. Look at each one: if a single file already holds the whole session, upload that one and skip the merge.

Does merging change anything in my Zwift account?

No. FitMerge only reads the files you downloaded and changes nothing on Zwift, so both parts stay in your Zwift activities unless you delete them there. If you do, note that Zwift's help calls deleting an activity permanent.

Are my watts smoothed or averaged out?

The samples go across as Zwift recorded them. Only the totals shown above the map, like average power, are worked out again over both parts together.

My files came from Zwift on two different devices. Does that matter?

Not to the merge. A part from the laptop and a part from the phone join the same way, as long as one ends before the other begins.

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