Connecting Your Watch with intervals.icu

The tracker has no direct partnership with watch manufacturers. It does not need one: it goes through intervals.icu, a service that knows how to talk to every brand and that gives the original files back. You connect your watch to intervals.icu once, you paste a key into the tracker, and your sessions arrive on their own from then on.

Why the detour

A GPS watch records every session in a FIT file: the track, heart rate second by second, power, altitude. That file is what the tracker reads to compute your load, your zones, your vertical speed curves and your segments. Getting that file from the manufacturer requires a commercial agreement with each of them, and a different integration every time. intervals.icu, on the other hand, connects natively to Garmin, COROS, Suunto, Polar and Wahoo, and keeps the original FIT.

Step 1 — Create an intervals.icu account

Go to intervals.icu and create an account. It is free, with no time limit, and the service runs on a donation model.

Step 2 — Connect your watch, directly

In intervals.icu, open Settings, then the connections section. Pick your watch brand and authorise access. Garmin, COROS, Suunto, Polar and Wahoo each have their own button.

⚠️ Do not go through Strava. intervals.icu can also import from Strava, but Strava's terms of use forbid the reuse of that data by a third-party service. The tracker deliberately ignores any activity whose source is Strava: it will be counted as seen, and skipped. You would see your sessions in intervals.icu without ever seeing them reach your plan.

Once the connection is made, your past sessions come up into intervals.icu, and new ones arrive automatically after each watch sync.

Step 3 — Get your API key

Still in intervals.icu, open Settings and scroll down to Developer Settings. There you will find your API key, a long string of characters. Copy it. It is personal: it gives read access to your data, do not share it.

Step 4 — Paste the key into the tracker

In the tracker, Settings tab, Tracking equipment section. The intervals.icu key is the first field of the section. Paste the key. Just below it, Sync history decides how far back the first import goes: thirty days by default, up to a year. Thirty days is enough for the tracker to have something to work with from the first week; go further back if you want your performance curves to cover last season. Save. The sync starts.

What happens next

• The tracker only fetches FIT files. An activity entered by hand in intervals.icu, or imported as GPX, is recognised then skipped: there is no data to draw from it.
• Each session is imported only once. The tracker remembers the identifiers it has already seen, and also checks that the file is present before any download.
• The window moves forward on its own. After the first import, each sync only asks for the days elapsed since the previous one, with three days of overlap to catch up a watch synced late.
• The sync starts when you open the tracker, in the background, at most once every six hours. A Sync now button is there if you are in a hurry.
• Nothing is ever written to intervals.icu. The connection is read-only.

If something does not come through

A session is missing. First check that it is indeed in intervals.icu, and look at its source: if it comes from Strava, it will not be imported. Reconnect the watch directly and the activity will come through again. Nothing arrives at all. An invalid key gives an explicit error in the tracker. Take the key again from Developer Settings, checking that no space slipped in when pasting. You changed watches. Nothing to do on the tracker side: the key belongs to your intervals.icu account, not to the device. Connect the new watch in intervals.icu and the sessions keep arriving. A watch left several days without syncing. The three-day overlap covers the ordinary cases. Beyond that, run a Sync now after syncing the watch: the window restarts from the last success.

What if I do not want yet another account?

That works too, and the tracker plans for it. The Import files area at the bottom of the week accepts your files by hand: .fit, .fit.gz, and the .zip archives exported from TrainingPeaks. You keep full control, at the price of one gesture after every outing. Automatic import adds nothing to the analysis. What it adds is not having to think about it.