What you need

1. An iPhone and the Autocast app

The app needs iOS 26.0 or later. It asks your permission for Bluetooth (to talk to the adapter), location (for your route) and motion (for acceleration and g-forces).

About the app

2. A Bluetooth OBD2 adapter

Choose an ELM327-compatible adapter that uses Bluetooth LE (Bluetooth 4.0 or later, sometimes sold as "BLE" or "for iPhone"). Older adapters that use classic Bluetooth only work with Android phones. Adapters vary a lot in speed: a faster adapter records more readings per second, which makes charts smoother and figures like acceleration times more precise.

These adapters score best across members' recorded drives:

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See every adapter and how it scores for your model →

3. A car with an OBD2 port

OBD2 became compulsory for new petrol cars in the United States from 1996, in Europe from 2001 and in Australia from about 2006, and for diesels a few years later; many cars had it earlier. Cars older than that can still go in your garage and logbook, but can't record drives. The port is usually under the dashboard near the steering column. Not every car reports every reading, and the readings available depend on the make and model.

Connecting for the first time

1. Plug the adapter into the car's OBD2 port and switch the ignition on (or start the engine).
2. Open the Autocast app and sign in with the same Apple or Google account you use on the website.
3. Go to Settings → Adapters and select your adapter from the list. Don't pair it in the iPhone's own Bluetooth settings: the app connects to it directly.
4. Optionally, turn on Auto Connect on the same screen and Auto Record in Settings → Preferences, so the app connects and starts recording whenever you get in your car.
5. Set up the recording before you drive off, and keep your phone in a mount. Never handle your phone while driving.

More help is in the app FAQs.