FITgap

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FITgap is a small, open-source iPhone app that downloads your original FIT files from Wahoo, Zwift, MyWhoosh, Hammerhead, Dropbox and intervals.icu, or imports FIT files you open in it. It saves them to Apple Health with every metric, lap and route, without duplicates, or hands them unchanged to apps like HealthFit through the native share sheet. Files are never converted or re-encoded.

• Requires iOS 17 or later, written in SwiftUI with native controls
• Light and dark mode, German and English interface (follows the iOS language, English as fallback)
• Two-column layout on wide displays such as the unfolded iPhone Duo and in landscape
• No backend, no tracking, no third-party dependencies

Features

• Wahoo, Zwift, MyWhoosh, Hammerhead and intervals.icu: Connect any of the accounts and load every activity with its original FIT file. Existing files are skipped on later syncs. Through intervals.icu, rides recorded on Garmin, COROS, Suunto, Polar and other devices are covered as well.
• Dropbox: Loads the FIT files that services such as Zwift, Wahoo ELEMNT, Karoo, Rouvy or TrainerRoad export automatically into /Apps in your Dropbox. Later syncs only fetch changes.
• Import FIT files: Open .fit files in FITgap from the Files app, Mail or another app, or pick several at once in the app, for example exports from Garmin, TrainerRoad, Rouvy, Bryton or Karoo, or files from iCloud Drive, Dropbox or Google Drive. Invalid files are rejected, and a file already in FITgap is not added twice. Imported activities take part in the duplicate check and the Apple Health export like any other source.
• Duplicates: When several sources deliver the same workout, the list shows only the copy with the most data streams and metrics; it is the one shared and saved to Health. The other copies stay stored and are listed in the details.
• Share: Hand one FIT or a multi-selection to the system share sheet, for example to HealthFit. Shared activities are marked in the list.
• Apple Health: Save activities as workouts with every record sample Health supports (heart rate, power, cadence, speed, running dynamics, distance, energy, swim lengths), laps, pauses, route and the session summary as metadata. Individually, by selection or automatically for new activities. Workouts already in Health, from FITgap or another app, are detected and skipped.
• Details: Distance, duration, average and maximum speed, heart rate, cadence, power, elevation and more, read locally from the FIT session summary.
• Route map: Rows and details show the recorded route on an Apple map, coloured by speed in soft pastel shades (coral slow, yellow average, mint fast) with start and finish; virtual rides from Zwift or MyWhoosh appear at the coordinates of their game world. Tap the map in the details to open it full screen and zoom in. Choose the map type, Standard or Satellite, under “Accounts” › “Map” or in the full-screen map. Activities without positions show no map.
• Search and filters across all downloaded activities: time period (last 7 or 30 days, last 12 months, this or last year), activity type and data source.
• Files app: Every downloaded FIT is also available under On My iPhone › FITgap.
• Large archives: Paged syncing with resume, respect for Wahoo and Dropbox rate limits, and cancellable downloads. On iOS 26 and later, a sync or Health export you started keeps running after you leave the app, with progress in the Dynamic Island.
• Integrity: Downloads are stored atomically and verified with SHA-256 before sharing.
• Demo mode: Try the app without an account using three synthetic sample rides with routes, including the Apple Health export. Resetting or ending the demo removes the demo workouts from Health.
• Startup log: Accounts › Diagnostics › Share Startup Log hands a local text file with launch timings (app version, device model, iOS version, number of activities) to the share sheet, for example to attach it to a support email. It is only written on the device and never sent automatically.

Build and run

1. Open FITgap.xcodeproj in Xcode and select the FITgap scheme.
2. Under Signing & Capabilities choose your own team and, if needed, set your own unique bundle identifier.
3. Select a simulator or your iPhone and run.

Run the Swift package tests with:

swift test

The iOS keychain, sync lifecycle and UI tests are part of the Xcode scheme.

Using your own accounts and API access

• Wahoo uses OAuth 2.0 with PKCE (fitgap://oauth/wahoo, scopes user_read workouts_read) and a public client ID, no client secret. The client ID is defined in Sources/FITgapCore/WahooOAuth.swift. If you build your own version, register your own application in the Wahoo Cloud API portal and use its client ID and redirect URI.
• Zwift has no public API. FITgap uses unofficial interfaces with a public client ID, which Zwift may change or restrict at any time. Your password is only used transiently for sign-in and is never stored.
• MyWhoosh has no public API either. FITgap signs in with your email and password through the unofficial interface of the MyWhoosh apps and stores only the access token and your account ID (WhooshId). No token refresh is known, so an expired session requires signing in again. FIT files are fetched through signed download links without the access token. MyWhoosh may change or restrict this interface at any time.
• Hammerhead uses its official API with OAuth 2.0 (scope activity:read). Hammerhead requires a client secret for every token request and offers no PKCE, so the app has to carry the secret. It never enters the repository: put it into Config/Secrets.xcconfig (copy Config/Secrets.example.xcconfig; Xcode Cloud writes it from the secret environment variable HAMMERHEAD_CLIENT_SECRET in ci_scripts/ci_post_clone.sh). At build time scripts/hammerhead-secret.sh masks it with a random key per build; masking only slows down extraction from the app. Without a secret the app builds normally and hides Hammerhead. Hammerhead only accepts http(s) redirects, so the registered redirect is the static page docs/oauth/hammerhead/ on GitHub Pages, which hands code and state to fitgap://oauth/hammerhead without loading anything else. For your own version, create an API client in the Hammerhead Dashboard, register that page (or your own copy) as redirect and change the client ID in Sources/FITgapCore/HammerheadOAuth.swift.
• Dropbox uses the official API v2 with OAuth 2.0 and PKCE as a public client (redirect db-<app key>://2/token, the scheme Dropbox provides for mobile apps; token_access_type=offline for a refresh token), so there is no client secret. FITgap requests only files.metadata.read and files.content.read. An App folder app would need the least access, but it can only see its own folder under /Apps, while Zwift, Wahoo, Karoo and others write into their own folders there. So FITgap needs access, kept read-only by these two scopes; it lists recursively, downloads only files and checks each against the Dropbox content hash and the FIT header before storing it. The app key is set in ; while it is empty, the app hides Dropbox. For your own version, create an app with and in the , enable the two scopes, allow public clients (PKCE) and enter its app key; the redirect follows from the key.

Privacy

• Access and refresh tokens and the intervals.icu API key are stored only in the local keychain (WhenUnlockedThisDeviceOnly, no iCloud sync).
• Activities and FIT files are stored on the device in Application Support/FITgap/. Nothing is sent to a server operated by the project.
• Apple Health access is optional. FITgap writes workouts and only reads workouts to detect duplicates; no Health data leaves the device through FITgap.
• Maps are drawn with Apple MapKit. To show the map, Apple's map service receives the visible map region and the usual connection data; the route itself is drawn on the device.
• Disconnecting removes the local session; the authorisation at the provider remains, except for Hammerhead and Dropbox, where FITgap revokes it. Downloaded files remain.

See the full Privacy Policy.

Project layout

Path	Contents
App/	SwiftUI app, localisation (de.lproj, en.lproj), assets
Sources/FITgapCore/	Provider access, keychain, storage, FIT summary reader, demo data
Sources/FITgapProbe/, Sources/WahooProbe/	Small macOS command-line clients for API experiments
Tests/, AppTests/, AppUITests/	Package, iOS and UI tests
scripts/	Helper scripts, e.g. generate-demo-fit.py for the synthetic demo files
Assets/	Brand and App Store artwork
docs/	Project website (GitHub Pages)

The bundled demo FITs contain no personal data or real GPS positions; they are virtual rides on made-up loops in the open South Pacific. They were generated synthetically with Garmin's official Python FIT SDK, which is only a development tool and not an app dependency.

Contributing

Issues and pull requests are welcome. By submitting a contribution you agree that it is licensed under the Apache License 2.0 (section 5 of the license). Please keep changes focused and match the existing code style.

License

Licensed under the Apache License 2.0. The name FITgap, the logo and the app icon are not covered by this license and may not be used to identify modified versions or derived apps; see NOTICE.

The App Store version is a convenient, paid build of this same source code. You are free to build the app yourself.

FITgap is an independent project and is not affiliated with or endorsed by Wahoo, Zwift, MyWhoosh, Hammerhead, Dropbox, intervals.icu, Garmin or HealthFit.