Frequently asked questions

FIT, GPX and TCX — the formats bike computers, watches and training platforms record and exchange. You can mix formats in one merge: a GPX from a bike computer and a FIT from a watch merge just as well as two files of the same type. Every uploaded file gets a health-check report (points, time range, stream coverage, damage diagnosis) before anything is merged.

Free: 3 merges per month, up to 2 files per merge, up to 5 MB per file. Starter ($9/month): 30 merges per month, up to 10 files per merge, up to 15 MB per file. Pro ($19/month): 300 merges per month, up to 20 files per merge, up to 30 MB per file. Limits are checked on the server as soon as a file is uploaded, and anything over a limit is refused with a clear message — never silently truncated.

Writing valid FIT is the hardest part of what FitMerge does: the binary format, its checksums and its required records have to be exactly right or Garmin and other tools reject the file outright. FIT export — and damaged-FIT repair — are the paid core of the product (Starter and Pro). GPX and TCX export cover the same merged activity and are free on every plan, so you can run the full workflow and check the reconciliation before paying anything.

Repair can recover the recorded points from a truncated file (for example when a battery died mid-save), correct or work around CRC checksum errors, and rebuild a missing session record from the data that is present. Every repair comes with a report of what was wrong and what was changed. Repair cannot invent data that was never recorded: if the device stopped writing before the end of your ride, that section stays missing, and the report says so plainly.

When two files record the same activity at the same time, FitMerge aligns them on their timelines. You then pick the source file for each data stream separately — GPS, elevation, heart rate, cadence, power and temperature can each come from a different file — and the merged activity takes the chosen stream from the chosen device. The totals reconciliation shows the resulting coverage of each stream, so you can verify nothing was lost.

Stitching joins files end to end in time order — use it when one activity was recorded in pieces, such as a paused computer or a device swapped mid-ride. Stream-by-stream merging combines files that overlap in time — the same activity recorded on two devices at once. The health check shows each file's time range, which makes it easy to see which mode your files need.

That is what the output is built for: merged files are written to the FIT, GPX and TCX specifications, with valid structure and checksums, and the reconciliation lets you verify the totals before you upload. A repaired FIT file likewise comes out as a valid file rather than a patched one. If a platform ever rejects a file we produced, contact support with the error message and we will investigate.

Files are processed on our server and stored only so you can review the health check, make your merge choices and download the results. They are deleted automatically 24 hours after processing, and you can delete them sooner yourself. We never sell or share your activity data. See the privacy policy for the full details.

No. The free plan works without signup — upload, merge, and download. An account adds your merge history; paid plans add FIT export, FIT repair, higher limits, and, on Pro, saved stream profiles.

A stream profile saves a device combination: which of your devices provides each data stream (GPS from the computer, heart rate from the watch, and so on). When the same devices record together again, the profile applies your usual choices in one click instead of picking six sources by hand. Stream profiles are a Pro feature, and they store your source preferences only — not your activity data.

The merged activity in your chosen format — GPX or TCX free, FIT on Starter and Pro — plus the totals reconciliation (points, distance, duration and per-stream coverage checked against the inputs) and, when a file was repaired, the repair report.

Subscriptions are billed monthly in USD through Paddle, our merchant of record. Paid features unlock only when our server confirms your subscription. Cancel anytime via the link in your Paddle receipt email; your plan stays active until the end of the paid period, then returns to Free. See the refund and cancellation policy for refund terms.