Frequently asked questions
Are my files uploaded anywhere?
No. ButterLaps runs entirely in your browser – your file is parsed, edited, and exported on your own device and never sent to a server. The only network request the app makes is a one-off licence-key check when you unlock unlimited use, and your activity data is never part of it.
Does ButterLaps change the rest of my activity data?
No. ButterLaps rewrites only the lap messages in the file. Your GPS track, heart rate, power, cadence, elevation, sensor streams, developer fields, and every other byte are preserved exactly as recorded. The original file is never modified – the app always writes a new .fit for you to download.
Will Strava, Garmin Connect, and Stryd still accept the file?
Yes. The exported file is a valid .fit with only its lap boundaries changed, so Garmin Connect, Strava, Stryd, HealthFit, and the other platforms read it the same way they read the original. As always, keep your original file and check the export in your platform before deleting anything.
Which devices and apps does it work with?
Any valid .fit activity file. That includes recordings from Garmin, Wahoo, and COROS, plus Apple Watch workouts exported via HealthFit, WorkOutDoors, or the Stryd app – and most other devices and apps that produce standard .fit files. ButterLaps is an independent tool and isn't affiliated with any of these companies.
What does "per-lap dev field summaries cleared" mean?
When you move a lap boundary, the per-lap summary values of custom developer fields – for example Stryd's per-lap metrics – no longer match the new split and can't be recalculated, so they're dropped for the affected laps. Your full-resolution record stream is untouched, and most apps recompute lap statistics from it anyway.
What's the difference between laps and intervals?
A lap is a segment of your activity. It gets marked when you press the lap button, by Auto Lap (every kilometre or mile), or automatically at each step of a structured workout – so if you ran a structured session, you usually already have one lap per warm-up, rep, recovery, and cool-down. Laps are the splits Strava and most tools display, and they're exactly what ButterLaps edits.
So where does the confusion come from? Recent Garmin watches write a second, independent set of "split" data alongside the laps – computed on the watch from your pace and cadence, not from your lap presses. Garmin Connect's "Intervals" view is built from that data, not from your laps. The two sit side by side and don't reference each other, which is why your splits can still look wrong in Garmin Connect even after the laps are correct: you're looking at the device's separate interval layer, not the laps you edited.
ButterLaps edits the lap messages and preserves that interval layer by default, so nothing else in your file changes. If the stale "Intervals" view is the problem, there's an export option that clears the split data so Garmin Connect rebuilds the view from your edited laps instead. This quirk is specific to recent Garmin devices – Strava, Stryd, HealthFit, and others read the laps directly, so they reflect your edits straight away.
Is ButterLaps free?
Yes – ButterLaps is free and unlimited during the public beta. Basic use will always stay free; after beta, a one-time licence will unlock heavier use. There's no account to create and nothing to install.
How do I get support?
Email [email protected] and tell us what went wrong – the more detail, the better. Attaching the original .fit file makes troubleshooting far easier, but that's entirely your call: nothing leaves your device unless you choose to send it.