Sync your workouts across devices — free.

Why cross-device sync matters for training

Most people log their workouts on a phone because that is what they have at the gym. But reviewing data — checking volume trends over six weeks, planning the next mesocycle, comparing this month's squat numbers with last month's — is far easier on a larger screen.

The gap between logging device and analysis device is a real friction point. If your data lives only on one device, you either squint at charts on a small screen or you stop reviewing altogether. Neither outcome is good for long-term progression.

Sync also covers the basics: starting a session on your phone at the gym and finishing the notes at home on a tablet, or checking what you lifted last week before you leave for the gym. These are small conveniences, but they add up across hundreds of sessions.

How offline-first sync works in SammaGym

SammaGym is built offline-first. That phrase has a specific technical meaning: the app writes every workout, every set, and every progression note to local storage on your device first — before any network call is attempted. The local database (IndexedDB, via Dexie.js) is the source of truth, not a remote server.

When you sign in to your SammaGym account, the app syncs the local database to the cloud. From that point, any other device where you are signed in to the same account receives the same data. The sequence is always: write locally, sync when connected — never the other way around.

• Log at the gym. Your phone writes the session to its local database. No internet required.
• Connect to Wi-Fi or mobile data. The app detects the connection and syncs automatically in the background.
• Open SammaGym on another device. Your session, weights, RIR ratings, and progression notes are there.
• Conflict resolution. If you log on two devices while offline and sync later, the app merges the sessions without data loss.

This architecture means that a poor gym signal — or no signal at all — never interrupts a session. The app never waits for a server response to save a set.

Your data is yours — the privacy angle

Offline-first is not only a reliability decision. It has a meaningful privacy implication: your training data exists on your device independently of any server. If SammaGym's cloud went offline tomorrow, you would still have every session you ever logged, fully intact, locally.

Many fitness apps treat your data as a resource that lives on their servers — you are granted access to it through the app. If your subscription lapses or the company changes its terms, access can be restricted. SammaGym's model inverts this: the device holds the data, and the cloud is a copy you opt into, not a gatekeeper.

Sync is optional by design. You can use SammaGym for years without ever creating an account. If you later decide you want cross-device access or a cloud backup, you sign in and sync. Nothing is forced.

What you can do on each device

SammaGym is a Progressive Web App (PWA), which means it installs and runs on any device with a modern browser — phone, tablet, or desktop — without a separate download for each platform.

The interface adapts to the screen size. On a phone, the logging screen is thumb-first with large tap targets. On a tablet or desktop, the same data spreads into a wider layout with more visible at once — volume charts, the full exercise list, and progression history side by side.

If you prefer to keep the app installed for offline use, you can add it to your home screen from any browser's share or install menu. For details on installing SammaGym as a home screen app, see our guide on adding SammaGym to your home screen.

Sync is optional — the app works fully offline

It is worth being direct about this: you do not need to create an account or enable sync to use SammaGym. The full feature set — logging, auto-regulated progression, rest timer, cardio GPS, progress photos, PR tracking — works entirely offline on a single device.

Sync is an option for people who want cross-device access or a cloud backup. It is not a prerequisite for the core experience. If you train at a single gym with your phone and never want your data to leave the device, that is a completely supported use case.

This distinction matters because many apps described as "offline capable" are actually just cached versions of a server-dependent experience — they queue writes and fail gracefully when offline, but the data model is still fundamentally remote. SammaGym is the opposite: it is a local app that optionally replicates to the cloud.

For a deeper look at how the offline architecture works in practice, see our article on using a free workout app that works offline.

How to get started

Getting SammaGym running on multiple devices takes a few minutes.

• 1Open app.sammagym.com on your primary device (usually your phone) and install it by choosing Add to Home Screen from your browser's share menu.
• 2Use the app offline for as long as you like. Every session is saved locally.
• 3When you are ready to enable sync, create a free account inside the app. Your local history is uploaded and linked to your account.
• 4On any other device, open app.sammagym.com, sign in to the same account, and install the PWA. Your full history syncs down automatically.
• 5From this point, sessions logged on any device sync to all others whenever a connection is available.

If you are comparing SammaGym with other free options, our guide to the best free workout app that works offline covers the landscape with the same honest approach.