How to Open and Analyze a FIT File on iPhone
Short answer: the fastest way is an online viewer in your browser – the most private way is an app that supports "Open in" and reads the file directly on your iPhone, without uploading it anywhere.
What's actually inside a FIT file?
FIT (Flexible and Interoperable Data Transfer) is Garmin/ANT+'s compact binary format, produced by most sport watches and bike computers when they record – Garmin, Wahoo, Coros, Suunto, Hammerhead and others. Unlike GPX, it stores power, heart rate, cadence and elevation as a time series alongside GPS, usually once per second. That makes it the most accurate source for metrics like Normalized Power or time-in-zone – but also a pure raw-data format that no ordinary text editor or photo viewer can open.
One consequence worth stating plainly: iOS has no built-in preview for FIT files. Tapping one in the Files app on its own does nothing useful. That isn't a broken file – iOS simply has no idea what to draw until an app registers for the type.
Step 1: get the file onto your iPhone
The file usually starts out in your device maker's cloud, and the export almost always lives in the web portal rather than the phone app:
| Platform | Where the export lives |
|---|---|
| Garmin Connect | Open the activity → gear icon (top right) → Export Original |
| Strava | Open the activity → "···" menu → Export Original |
| Wahoo (ELEMNT) | ELEMNT app → workout → Export, or pull the .fit straight off the device over USB |
| Coros | Coros web portal → activity → download icon → FIT |
| Zwift | Files are written locally: Documents/Zwift/Activities on the recording machine |
| Polar / Suunto | Flow / Suunto app → activity → export as FIT or TCX |
Note the wording: "Export Original" is the one you want. An "Export GPX" gives you a much smaller file with the GPS track but no power and no heart rate – enough for a map, useless for training analysis. From a Mac you can also AirDrop the file, or mail it to yourself; either way it lands in the Files app or straight in the share sheet.
Option 1: an online viewer in the browser
The fastest route without installing anything: upload the file in Safari to one of the common online FIT viewer sites, which render it as a table, chart or map. Handy for a quick one-off look – but technically "upload" means exactly that: your heart-rate trace and the GPS route of your regular loop leave the device and briefly sit on someone else's server. Fine for a one-time curiosity check, not something everyone wants for routine training data.
Option 2: an app that reads it on-device
The alternative is an app that accepts FIT files via "Share" or "Open in…" and processes them entirely locally – the file never leaves your device. That's exactly what Endurance Debrief does: instead of a raw data table, you get a finished analysis right away – zone distribution, Normalized Power, IF, TSS, aerobic decoupling and a short coach note, all calculated within seconds of import.
The whole thing in three steps
- Get the file: export it from your device maker's web portal (see the table above), or AirDrop/email it to your iPhone.
- Tap or "Share": tap the .fit file in the Files app, or choose "Share" from wherever it arrived.
- Pick the app: choose "Endurance Debrief" from the list – the analysis opens automatically, no upload involved.
Catching up on a backlog of sessions? Select several files at once (batch import) or, even simpler, turn on Apple Health import so new workouts come in automatically as soon as they land in Health.
FIT vs. TCX vs. GPX — which one should you keep?
If the portal offers you a choice, the ranking is unambiguous:
| Format | Contains | Good for |
|---|---|---|
| FIT | power, HR, cadence, temperature, laps, developer fields – binary, ~1 Hz | everything; the only format with the full picture |
| TCX | HR, cadence, laps – XML, larger files | a decent fallback when FIT isn't offered |
| GPX | GPS track, sometimes HR – XML | maps and routes, not training analysis |
Practical upshot: archive the FIT. You can always derive a GPX from it later, but you can never recover power data from a GPX that never had it. If you want to see what the numbers derived from that file actually mean, our guide on how TSS is calculated covers the metrics an analysis app builds from this data.
When the file won't open
Three causes account for almost every case:
- It's still a ZIP. Garmin Connect delivers bulk exports as an archive. Tap it once in the Files app to unpack it, then open the .fit inside.
- You exported a summary, not the original. A file with no time series in it will open but show nothing – re-export with "Export Original".
- Nothing is registered for .fit. If the share sheet offers no sensible target, no installed app has claimed the file type yet. Installing one that reads FIT fixes it immediately.
One thing that is not a cause: needing a Garmin account. FIT is an openly documented format and isn't tied to any login – if you have the file, you can open it.
Frequently asked questions
Can the iPhone open a FIT file natively?
No. FIT is a compact binary format, so iOS has no built-in preview – tapping the file in the Files app shows nothing useful on its own. You need either an app that registers for the .fit type or a web-based viewer. The file isn't broken; iOS just has no idea what to draw.
How do I export a FIT file from Garmin Connect or Strava?
Both exports live in the web portal, not the phone app. In Garmin Connect: open the activity → gear icon (top right) → Export Original. In Strava: open the activity → "···" → Export Original. "Export GPX" gives you a smaller file without power or heart rate, so choose Original if you want the full data.
What's the difference between FIT, TCX and GPX?
GPX carries little more than the GPS track – smallest, least useful for training analysis. TCX is XML-based and adds heart rate, cadence and laps. FIT is Garmin's compact binary format and holds the most: power, heart rate, cadence, temperature, lap structure and developer fields, usually once per second. For accurate Normalized Power or time in zone, always keep the FIT.
Is it safe to use an online FIT viewer?
It works, but "upload" means exactly that: your heart-rate trace and the GPS track of the route you ride from your front door leave the device and sit on someone else's server, under that site's retention policy. Fine for a one-off curiosity check. For routine training data, an app that parses the file on the phone avoids the question entirely.
Why does my FIT file not open on my iPhone?
Usually one of three things: the file is still zipped (Garmin bulk exports arrive as a ZIP – unpack it in the Files app first); you exported a summary rather than the original, so there's no time series in it; or no installed app has registered for .fit, leaving the share sheet with nothing sensible to offer. The last case is fixed by installing an app that reads FIT.
Can I open a FIT file without a Garmin account?
Yes. The FIT format is openly documented and isn't tied to a Garmin login. As long as you have the file itself – from a watch, a bike computer, a Zwift export or a backup – any app that reads FIT can open it, no account with anyone required.
Endurance Debrief reads .fit, .tcx and .gpx files directly on the iPhone – and, as of version 2.0, on the iPad just the same. No uploads, no server, no account. Import via "Share", Files or AirDrop, one at a time or in a batch.