What is FIT File Viewer?
Most tools that open a FIT file show you a summary. FIT File Viewer shows you the file. Drop one on the page and it decodes every message inside into its own collapsible table: File ID, Device Info, Event, Record, Lap, Session, Activity, and whatever else the device wrote. The Record table is your ride second by second, with position, heart rate, cadence, distance, power, speed and altitude as columns, paginated, filterable by time. Flip the switch to Developer Mode and you get the raw values from every message and field, documented or not, with undocumented ones marked so you know they are guesses.
That is why it feels like an editor rather than a viewer. You are not looking at a chart someone drew from the data; you are looking at the data, the way the device stored it, and you can see exactly what Strava or Garmin Connect saw when they imported it.
It does not connect to Strava. You get the file out yourself: on an activity page, the three-dot menu has Export Original, which hands back whatever your device uploaded. If that was a FIT file (Garmin, Wahoo, COROS and most head units), FIT File Viewer opens it. If the activity was recorded in the Strava app or uploaded as GPX, there is no FIT to export.
Key Features
Tables for everything
Click a message header and its table opens. Ten, twenty or fifty rows a page, a time search on the timestamp column, and a raw or decoded toggle. Connect IQ developer fields are decoded too, with a link to the app that wrote them.
Chart and map
Pick any two record fields for the two axes, drag to zoom into a stretch, and it shows the averages for the range you selected. The map draws the route with start and finish pins and numbered lap markers.
Exports
Any table as CSV, with a choice of timestamp format for spreadsheets. The route as GPX, with laps as waypoints if you want them. Chart data as JSON. If the file has HRV messages, the RR intervals as a text file.
It fixes broken files
This is the feature people arrive for. A watch that died mid-ride or an app that crashed before writing the end of the file leaves a FIT that Garmin Connect and Strava refuse. FIT File Viewer is deliberately stricter than either: it spots missing or invalid File ID, Lap, Session and Activity messages, duplicate records, bad CRCs and truncated files, marks the problems in red, adds what is missing in blue, and offers a fixed copy to download and upload by hand. A Garmin forum user with an Enduro 3 called it the only tool that recovered duplicated records and produced a file Garmin Connect would take.
Nothing leaves your browser
Parsing runs locally. The only time a file goes anywhere is if you choose to submit it through the decoding-problem form. Anonymous device and issue stats are collected, with a checkbox to opt out.
Who It's For
- Anyone with a corrupt FIT file that Strava or Garmin Connect will not accept
- Developers decoding what a device actually writes, including fields the SDK does not document
- Data-curious athletes who want the second-by-second numbers behind a ride in a spreadsheet
- Connect IQ users checking whether a data field recorded what it was supposed to
