Repair a broken FIT activity file

Choose a .fit file that Strava, Garmin Connect or another app refuses to upload. This page shows what is wrong with it, for free.

Your file stays on your computer. It is read inside your browser; none of your files are uploaded. The repair code sets no cookies. Site visit analytics are described in our privacy policy.

What it fixes

These are the problems it looks for and repairs:

• A wrong or missing checksum at the end of the file, or a wrong header.
• A recording that was cut off, for example when the battery died or the app crashed. It attempts to keep the readable recording before the cut.
• Damaged stretches in the middle. The damaged part is skipped and the rest is usually kept. If damage changes a timestamp, data points after it can be removed as well, and the page warns you when it can tell that a lot was lost. It cannot always tell, so check the result against what you expected.
• The lap, session and activity summary at the end of a recording that was cut off. It is rebuilt from the data points that survived.

What it cannot fix

• Anything after a cut-off point. If the file stops at minute 40 of a 90 minute ride, minute 41 onwards is not in the file, so it cannot come back.
• Data inside a damaged stretch. Those data points are dropped, not guessed.
• Wrong values in a file that still opens. If a damaged record left a bad number behind, such as a jump in distance, the file can open and still show it. This tool does not check values.
• Rebuilt totals are estimates. Duration, distance and averages in a rebuilt summary are worked out from the surviving data points, and the sport is usually set to a generic type. You can change the sport after you upload. If a lap or session message in the middle of a file was destroyed, the totals can also disagree with the laps that survived.
• Damage near the start of the file. If the definitions that describe the file's layout are damaged, most or all of the recording can be unreadable. The page then says how little was recovered, or that it could not repair the file. It does not always notice, so compare the repaired file with what you expected.
• A file whose structure and checksums are intact is never modified. The page says so and offers no download. If Strava or Garmin Connect still refuse it, the cause is probably in the values, and this tool does not look at those.
• It does not merge files or edit an activity. It only repairs the file you give it.
• A file that is not a FIT file, or that has no readable activity data left, cannot be repaired. The page says so.

What "repaired" means

The tool attempts to repair the header and checksum and keep readable parts of the recording. Independent scripts decoded repairs of three real broken files with Garmin's FIT SDK and a second FIT reader, and checked their lap and session totals. These test checks are not run on your file by this page or the downloadable tool. Repair attempts can still fail to open elsewhere or have disagreeing totals.

Acceptance by Strava and Garmin Connect has not been confirmed. Keep your original. Compare the first and last timestamps in the diagnosis with when you recorded the activity; they are in UTC, and their span is not moving time. After opening a saved repair in an activity viewer, or after an accepted upload, compare its distance, duration and activity details with what you recorded. This page does not display distance or duration. Real Zwift files have not been tested.

Save a repaired file

The diagnosis is free. The downloadable offline repair tool uses the same repair code and lets you save repaired files. Buying it does not promise a better repair. After buying, unzip it, open FITRepair.html and choose your original file again.

Privacy

The file is read and repaired inside your browser, on your computer. It is not uploaded and not stored. The repair code sets no cookies. Site visit analytics are described in our privacy policy. Closing the tab clears it.

Built and maintained by Madrasco with AI agents. Questions or refunds: [email protected]. You can ask for the human owner. Refund policy.

Questions

Will my file be changed if it is fine?

No. If nothing is wrong, the page says so and offers no download. Your file is never modified.

Which devices and apps does it work with?

It is meant for FIT activity files from any device or app. We have tested files from Garmin, Wahoo, Coros and Strava. We have not tested every device, and we have not tested real Zwift files.

Is this advice for training or health?

No. It repairs the structure of a file. It does not judge the data, and you should not rely on repaired figures for anything important.