A Workout App That Works Offline

Anvil Workout runs entirely on your device. No account to create, no server dependencies, no internet connection required. Your programs, workout history and personal records stay on your iPhone or iPad, and the Apple Watch follows the workout without a connection, so a gym with no signal doesn't matter.

What "offline" actually means

"Works offline" can mean anything from logging a set without signal to needing a connection to sign in, start a workout or save it. For Anvil Workout it means all of it:

• No account, ever. You install the app and start using it. No email, no password, no "create account" screen.
• No cloud service. There is no Anvil Workout server. Nothing to go down, nothing to get breached, nothing to paywall later.
• Your history stays on your device. Your programs, sets, reps and personal records are never uploaded or synced. The iPhone and the Apple Watch companion talk to each other directly over local connectivity (WatchConnectivity), with no server in between. The only thing the app sends is a crash report to Sentry when something goes wrong, with no workout data in it, and you can turn it off in Settings.
• HealthKit integration is local. If you let the app write workouts to Apple Health, that happens on-device through Apple's HealthKit APIs. Apple decides where HealthKit data goes, not us.

When offline actually matters

Gym basements with no signal

The squat rack is usually in the back corner of the basement of the building, and that's exactly where cell service dies. An app that needs to phone home between sets is an app that freezes mid-workout. Anvil Workout doesn't care. Your workout runs the same whether you're in airplane mode or on 5G.

Travel, planes, and remote training

Hotel gyms, garage gyms, outdoor calisthenics, a cabin in the woods with no Wi-Fi. If you can open the app, you can train. Apple Health lives on the iPhone too, so a finished workout is saved there straight away, with nothing waiting to sync later.

Privacy

Your workout history is personal data. It reveals your schedule, your physical capacity, and patterns that can be combined with other leaks to identify you. We chose not to collect it, because the safest data is the data that never leaves your device. The one thing the app sends is a crash report when something goes wrong, which you can switch off and which contains no workout data. The privacy policy lists exactly what it holds.

Longevity of your data

Your history lives in the app's storage on your device, not in an account with us. If you use iCloud Backup or back up to a computer, it's included, and it comes back when you restore to a new phone. You can also export it as a CSV file whenever you like. The flip side is that there is no copy anywhere else, so your device backup is your only backup.

How it works under the hood

Anvil Workout is a native SwiftUI + SwiftData app. SwiftData is Apple's on-device persistence framework. Think of it as a private, local database optimized for Apple hardware. Your programs, session history, and exercise library all live in SwiftData on your device.

There is no backend service because there's nothing for a backend to do. Your iPhone is the server, the client, and the database, all at once.

What needs a connection

Everything you do in a workout works without one. These are the few things that touch the network, and why.

Part of the app	Connection
Programs and the library	None. Build, edit and import programs anywhere.
A workout in progress	None, including the rest timer. The phone itself updates the countdown on the Lock Screen, with no push server.
Apple Watch	No internet. It needs your iPhone nearby, because it follows the workout running there. If the two lose touch, the Watch catches up with the latest set when they reconnect.
History, records and Stats	None. Everything is worked out on the device.
Apple Health	None. Workouts are saved and read on the device.
CSV export and import	None to make or read the file. Sending it somewhere is up to you.
Crash reports	Sent when there is a connection, if you leave them on in Settings. They carry no workout data.
Updates	From the App Store, like any app.

Working without a server has a cost. Anvil Workout has no sync between iPhone and iPad, no web version and no social features. If you need those, choose an app built around an account. If you want a lifting log that never asks you to sign in and keeps your history on your devices, Anvil Workout is built for that.

Check it yourself

The surest test of any workout app is a whole workout with no connection. Turn on Airplane Mode before you open the app, start a workout from one of your programs, lock the phone through a rest, then finish the workout and open your history. Look for a sign-in screen, a spinner, a set that won't save or a workout waiting to upload.

In Anvil there are none. The rest counts down on the Lock Screen, the finished workout is in your history with any new records marked, and it's saved to Apple Health if you allowed it. The built-in programs are part of the app, so importing one works the same way. To bring your Apple Watch along, make sure Bluetooth is on, since the Watch follows the workout from your iPhone without the internet.