How to repair a corrupt FIT file (and get the activity onto Strava)

Which situation you’re in

• Strava said “partially corrupted file, could be truncated”. The activity is already on Strava with everything it could read. Strava says the missing part can’t be recovered. If the cut happened during a sync, the copy still on the device may be complete. Copy it off and upload that one instead (delete the partial activity first).
• Strava said “Corrupted time data”. Run the file through FIT File Tools’ Corrupt Time Fixer, which is the fix Strava’s own help names, then upload the result.
• Strava said the file is “Empty”. If the FIT is tiny (Strava mentions 72 bytes), there’s nothing in it to repair. Look for another copy, or log it as a manual activity.
• The device died or froze mid-activity, or a sync was cut off, and the file won’t upload anywhere. Copy the original file off the device, open it in one of the repair tools below, and upload the repaired copy on the Strava website. Bad timestamps: FIT File Tools. Lost GPS track: GOTOES GPS Race Repair. Over 25 MB: GOTOES Shrink FIT. Truncated or damaged: GOTOES, FIT File Viewer, FIT File Editor (all free) or FIT File Repair Tool (Windows, paid).
• Strava calls it a duplicate. An earlier copy is already there. If the copy on Strava is the broken one, delete it first, then upload. Deleting loses its kudos and comments (see Uploading).
• The file is over 25 MB. That’s Strava’s limit. GOTOES has a tool that thins out the records.

If what you actually want is to crop, merge or split an activity that uploaded fine, the merging and editing guide covers that, including what you lose when you delete and re-upload.

Why FIT files break

Garmin’s FIT SDK describes a FIT file as a short header, then the recorded messages, then a two-byte checksum at the very end, and says the Activity message is often the last message in the file and can be missing if the file is truncated. So a battery that dies or a transfer that stops partway leaves a file without its ending: no valid checksum, and often no summary of the sport and totals.

Garmin’s support page on failed uploads names faulty GPS data, losing power while recording, and a connection failure during a file transfer as common causes of corruption.

Match Strava’s message to the cause

On the time error, FIT File Tools’ own FAQ adds a second cause: combining two activities from different days, or from two devices whose clocks were more than a day apart. Strava’s prevention advice for the Garmin time bug is to install software updates, try a hard reset, and tell Garmin.

Strava’s upload API returns a generic status, “There was an error processing your activity.”, alongside a separate error with the reason, so an app that uploads for you may only show the first. Uploading the file yourself on the website shows you the specific message.

Get the original file off the device

Every repair starts from the file. Strava’s Garmin page points you to the original file, from the device’s Activity folder or exported from Garmin Connect. Where you can, use the copy on the device rather than one left by a failed sync.

Garmin

Connect the device by cable. On Windows it’s This PC, the device, Primary if it’s listed, then Garmin, Activity. On a Mac, the Garmin drive in Finder, then Garmin, Activity. Files are named by date and time, like 2024-04-06-15-30-00.fit. Garmin notes that devices with music storage, or that use MTP, don’t show up as a drive on a Mac and says to use a Windows computer for those. Strava’s Garmin page adds that if the device shows up as a drive, you can upload to Strava straight from that Activity folder.

If the activity did reach Garmin Connect, the gear icon on the activity page has Export File. It downloads as a zip, and Strava reminds you to unzip it before uploading.

COROS

COROS says its watches don’t store workout data on the drive you see over USB, so the file comes from the app: Activities, the activity, the three dots, Export Data, .FIT. If a workout never synced, COROS warns against uninstalling the app or resetting the watch, since either can lose the unsynced data. Its troubleshooting steps are a manual sync, restarting both (hold the power button 15 seconds), recording a one to two minute test activity to push older ones through, and updating the app and firmware. Deleted it by accident? The COROS app keeps deleted activities for 30 days under Activities, All Activities, Recently Deleted.

Hammerhead Karoo

The easy route is the Hammerhead Dashboard: Rides, the “...” menu, Download FIT. For a ride that never made it off the unit, Hammerhead’s PC instructions are to turn on Developer Options and USB Debugging, connect with a data cable, choose MTP as the USB configuration, and open Internal Storage, where the FitFiles folder holds saved activities.

Wahoo

On the ELEMNT ACE, BOLT 3 and ROAM 3, try a sync first: a ride uploads over Bluetooth to the Wahoo app (pull down on History to force it) or over Wi-Fi straight to Wahoo’s cloud (on the unit, Workouts, Sync). If it still won’t sync, Wahoo’s help covers copying it over USB: in the Wahoo app, Devices, the unit, Settings, turn on Allow USB access and Allow .FIT file access, then connect the powered-on unit with a data cable and copy the ride from the exports folder (a Mac needs an MTP app). Older ELEMNT, BOLT and ROAM models have their own article. The Wahoo app can also import a repaired .FIT (History, the plus button, Upload), but Wahoo says imported activities aren’t shared automatically: share it to Strava from the activity’s three dots, Sharing.

Suunto

Strava’s Suunto page covers it: in the Suunto app, open the activity, the three dots, Export FIT file, and send it to yourself so you can open it on a computer.

The repair tools

Garmin’s position, from its upload-error page: “Some third-party FIT file repair tools may be able to recover corrupted files.” It doesn’t provide or support any of them. These five each document a repair feature on their own site.

FIT File Tools

This is the site Strava sends you to for the time error. Its Corrupt Time Fixer handles files with bad timestamps and has a Normalize Time option for big jumps, and the fixed file comes back with “fitfiletools” in its name. The same site has a Section Remover, Time Adjuster, File Combiner, Break Remover and a FIT Inspector, among others. It’s free with no account, and its FAQ says uploaded files are deleted automatically within 24 hours. The limit is 50 MB.

GOTOES

GOTOES has two different repairs. GOTOES says its FIT viewer analyzes a file and shows a repair button when it finds corruption, then hands you the repaired file; if that doesn’t work, the site points you to the merge tool, which “Also Repairs Corrupted FIT files” in a different way. The changelog for March 15, 2026 added a last-ditch repair for Garmin files with no record table at all. When the GPS track itself is gone, GPS Race Repair builds one from a course file between your start and finish times. Shrink FIT thins out records for files too big for Strava. Free limits are 14 MB on the viewer and 14 MB per file on the merger, 25 MB on the shrinker; donors get double. Everything runs on GOTOES’ server. Check the tool page before you start: some features are for donors, including importing straight from Strava and the Garmin to Strava transfer.

FIT File Repair Tool

A Windows program built on Microsoft Access (the free Access Runtime works), with no Mac or web version. According to the maker, it detects and treats corruption automatically when it imports FIT, TCX or HRM files. The FAQ explains that when the damage is at the end, values like calories and sport can be missing because they’re written in the last messages of the file, and you can type them back in. It can send the repaired file to Strava, Garmin Connect or TrainingPeaks with one click, and has a batch upload to Strava for a whole history. A license is EUR 39 or $49 for the current version, EUR 45 or $55 with a year of updates, and EUR 49 or $59 with two. Version 8.17.41 came out on August 24, 2026.

FIT File Viewer

A browser app that lays out a FIT file as tables, charts and a map. The homepage lists recovering data from partially corrupted FIT files and downloading a fixed file for upload to Garmin Connect or Strava. Processing happens locally in the browser; a file is only sent if you choose to submit it so an issue can be investigated.

FIT File Editor

A browser editor whose repair page is aimed at a watch that died mid-activity or a sync that got cut off. Its repair page says it keeps every record it can read, drops the broken part and writes a valid file with totals recalculated, all in the browser. If the sport reads “Activity” afterward, set it again; the page explains that many devices write the sport at the end of the file. Some older devices use a compressed timestamp format it can’t read yet.

GoldenCheetah isn’t a repair tool, but if the file opens and the problem is a gap or a spike, its wiki documents fixes under the Tools menu for power spikes, gaps in recording and GPS errors.

Uploading the repaired file

File uploads happen on the Strava website, not in the app. Strava’s Suunto article says you “can only manually upload an activity file from” the website. Go to strava.com/upload/select (or the orange plus icon, Upload Activity, File) and choose the file.

• FIT, TCX and GPX are accepted, 25 MB or smaller, and the file has to contain actual workout data.
• Subscribers can upload 25 files at a time, everyone else 15.
• If the activity is already on Strava in its broken form, delete that one first, or the upload is refused as a duplicate. Strava says a deleted activity that gets restored comes back without its kudos and comments, and photos have to be added again; the editing guide has the safe order.
• A Garmin Connect export is a zip. Unzip it first.

If you also want the fixed copy on Garmin Connect, its manual import is under the cloud icon, Import Data. Garmin caps a manual upload at 99,999 points, which it says rules out activities longer than 27 hours at one-second recording.

What can’t be recovered

Anything the device never wrote. If the battery went with an hour to go, the file stops there, and no tool can invent that last hour. Strava says the same about truncated uploads: the missing part is gone. A repair gets you a file that uploads, with the summary rebuilt from the records that survived.

A FIT file Strava calls “Empty” has nothing in it to repair (see the table).

Next time

Garmin’s advice is to charge before you start, let the activity finish saving before powering off, and eject the device safely before unplugging it (not needed for MTP devices). The FIT File Repair Tool FAQ adds keeping the activity folder small and the firmware current.

Sources

• Strava Help: Why does Strava say my .FIT file is corrupted?, corrupted time data, empty file, bulk upload, getting activities to Strava, exporting from Garmin Connect, Garmin and Strava, Suunto app and Strava, restoring a deleted activity
• Strava developers: Uploads
• Garmin Support: unable to upload an activity file, manually uploading activities, manual upload size limits
• Garmin FIT SDK: FIT protocol and Activity file type
• COROS Support: unsynced workouts, exporting an activity, watch drive not detected, recovering deleted activities
• Hammerhead Support: downloading a FIT file from Karoo to a PC and Dashboard, downloading a FIT file
• Wahoo Support: uploading a ride from ELEMNT ACE, BOLT 3 and ROAM 3, adding or importing an activity in the Wahoo app, copying a ride over USB
• FIT File Tools: home, Corrupt Time Fixer, About and FAQ
• GOTOES: FIT file viewer, merge and repair, GPS Race Repair, Shrink FIT, Strava Email Uploader, donations, changelog
• FIT File Repair Tool: home, license prices, download, FAQ (PDF)
• FIT File Viewer
• FIT File Editor: repair a FIT file
• GoldenCheetah wiki: FAQ, data

Related reading

Merging, splitting and repairing Strava and Garmin activities covers cropping, merging, fixing bad GPS or heart rate, and the safe order for deleting and re-uploading. The Garmin Connect and Strava and COROS and Strava pages cover the automatic sync.