Frequently asked questions
Are my files uploaded anywhere?
No. Your file is parsed, edited, and exported entirely on your own device – no byte of it is ever in a network request, and there is no backend that could receive it. The app does make a few requests that never touch your file: a cookieless page-view beacon (Cloudflare Web Analytics), anonymous in-app event pings to our own service (which action you took and a rough size band of the activity, never any file contents), and – only if you buy or already hold a licence – a licence check and checkout with our payment processor. No byte of your file is part of any of them.
Does ButterLaps change the rest of my activity data?
No. ButterLaps rewrites the lap messages and re-syncs the session's lap count to match; everything else is left as recorded. Your GPS track, heart rate, power, cadence, elevation, sensor streams, and developer record data are preserved exactly as your device wrote them. 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.
What do I do with the exported file?
Upload it to whichever platform you use, the same way you'd upload any activity file – there's nothing ButterLaps-specific about the export, it's just a corrected .fit. If the activity is already uploaded there, delete that copy first: most platforms reject a second upload of the same recording as a duplicate, so the corrected file won't replace the old one on its own. Keep your original file until you've confirmed the re-uploaded activity looks right.
Which devices and apps does it work with?
Any valid .fit file from a running, walking, hiking, or cycling activity. 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.
Those four sports are the whole list: other activity types, swimming among them, are turned away when you open the file, so you find out before you've done any editing. A multisport recording such as a triathlon has to be split into one file per sport segment first, since ButterLaps edits a single activity at a time. 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, ButterLaps recalculates that lap's custom developer fields – for example Stryd's per-lap power, distance, and pace – from your own recording, and checks the result against your device's totals before writing it. A field that's constant across every lap in the file (a pod's configuration setting, not a per-lap measurement) is carried forward unchanged instead. Only a field that can't be recalculated or verified, and isn't constant, gets cleared on the laps you actually edited. Run the "Verify export" check to see exactly which named fields, if any, this happened to – it's measured from the file the export will actually produce, not predicted in advance. Your full-resolution record stream is untouched either way, 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: unlimited exports for a single payment. It never expires, there is nothing to renew, and it covers every future version of the editor. 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.