Inspect FIT activity files, recover complete records and export GPX
A local triage desk for damaged or awkward FIT activity files. Read the real binary message stream, preserve complete native and developer bytes, and separate checksum repair from missing-data recovery.
FIT Activity Triage
Try the complete eight-record sample, then the truncated sample. Missing final activity metadata remains visible; a new checksum does not manufacture it.
Supported scope: FIT protocol 1/2 with a complete 12/14-byte header; 16 MiB, 100,000 record messages and a 30-second worker limit. Sequential prefix salvage only, no resynchronization or encrypted/raw-memory repair. CSV projects documented standard sensor fields; GPX keeps valid timed coordinates and elevation only. No developer-field decoding, summary regeneration or guaranteed platform import.
Activity file
Required fields are marked with an asterisk.
Recovered activity workbench
Review your output, then save it to your device.
Make the next step clear.
Your findings, assumptions and next steps will appear here after you run the check.
FIT Activity Triage · https://fitnessfiles.kitforma.com/ · KitForma
Real FIT binary and CRC inspection
Record selection with CSV/GPX exports
Byte-preserving prefix recovery and audit
Understand the evidence.
Focused guides explain the rules, the edge cases and the checks worth doing before you act.
Understand FIT checksum repair and data recovery
A valid checksum and a complete activity are separate properties.
Read the guide ↗Field guide / 02Export recovered FIT records to GPX and CSV
Choose a range without silently changing original activity totals.
Read the guide ↗Field guide / 03Read FIT timestamp and developer-field findings
Distinguish a parseable message from a trustworthy measurement.
Read the guide ↗Before you start
Can this restore every corrupted FIT file?
No. It requires a complete recognized header and retains only the sequential complete-message prefix. Parsing stops at the first malformed or truncated message. It does not scan ahead for guessed record boundaries, invent samples, rebuild summaries or guarantee that a fitness platform will accept the result.
What does rebuilding a FIT file change?
It creates a new 14-byte header with the actual recovered data length and fresh header/file CRC values. Every byte of the complete original message prefix is retained, including unknown native and developer fields. The original file is never overwritten. A fresh CRC proves internal checksum consistency, not sensor accuracy.
Does selecting records change the FIT export?
No. Record selection and the optional non-increasing timestamp filter apply only to CSV/GPX. The separate prefix FIT export preserves all complete source messages. This prevents a filtered track from silently retaining misleading original lap or session totals.
Which sensor fields are exported?
CSV projects timestamp, latitude, longitude, altitude, distance, speed, heart rate, cadence and power when those standard scalar fields exist. GPX exports valid timed coordinates and optional elevation. Developer fields and other values remain in the prefix FIT bytes but are not decoded into the CSV/GPX projection.
Why does GPX contain multiple segments?
Invalid or untimed GPS records split the track and are omitted from GPX. Non-increasing times or gaps greater than five minutes also start a new segment. The report gives the point, segment and omitted counts. This is a visible conversion rule, not a reconstruction of the device’s pause events.
Are my activities uploaded anywhere?
No. FIT parsing runs in a local browser worker and generated files are downloaded from browser memory. No Garmin, Strava or other platform account is required. Files, coordinates, timestamps and sensor values are not included in analytics events.
Sources & assumptions
Formats, algorithms and supported features are documented below. Check the stated scope and inspect your output before using it.
- Garmin FIT protocol ↗
Definition messages, byte order, compressed timestamps and file CRCs are decoded from the FIT message stream.
- FIT activity file requirements ↗
A complete activity requires specific messages and summary fields; a recoverable record prefix may be insufficient.
- GPX 1.1 schema ↗
Track segments, coordinates, elevation and UTC times are exported in GPX 1.1 format.
Reviewed 2026-10-19. Read our methodology or report an issue.