A Warm Device is a real phone that is already running, with your Mobile App already installed and open. When one is available, your Mobile Run attaches to it and begins in about two seconds, instead of waiting for a device to be found, booted and loaded. You do not configure anything: Thunders keeps devices warm for you, and the Device picker tells you when one is ready.

This matters most where testing normally hurts. Booting a real handset is the slowest part of mobile testing, and authoring a test means running it again after every small edit. A Warm Device removes that wait from every single iteration.

Warm Devices are an Enterprise feature. If your plan does not include them, talk to your Customer Success Manager or contact our sales team, and they will walk you through what enabling them involves.

Open the Device picker in a Mobile Test Case. A pool or a device that is ready shows a Warm badge, and the tooltip explains it:

"A device is already running for this app and environment, so a run starts without waiting for one to boot."

The badge appears on Device Pools and on individual devices, so you can pick a warm one deliberately when you want the fastest possible start.

While a device is being made ready, the runner shows Preparing device... so you always know the difference between a device getting ready and a run that is stuck.

A Warm Device is matched to the exact thing you are about to run. It has to agree on all of:

Orientation is not part of the match, so rotating the preview never costs you a warm device.

The practical effect is that warmth follows the work you actually repeat. Run a Test Case, edit a step, run it again, and the second run reuses the device from the first.

Devices are claimed by the runs you start yourself from the editor, which is the edit-and-run loop where waiting hurts most.

They flow in from everywhere else. A run in a Test Set, a scheduled run and a run from your pipeline each leave their device warm for your organization when they finish. The capacity your overnight suite already paid for is waiting for whoever opens a Test Case in the morning.

A device is only ever reused inside the organization it has already served. A device that has run your Mobile App is never handed to another customer.

On Android, a device can be reused after a run. On iOS, a run only claims a device that has not been driven yet, because iOS gives no way to clear an app's data in place. iOS runs still benefit from devices that are already up, they simply do not inherit one that has already run a test.

About two seconds from Execute to the first step running. The device is already allocated, your Mobile App is already installed, and the app is already open, so the three slow parts of starting a mobile test have all happened before you pressed Execute. Starting a device from scratch is an order of magnitude slower, which is the wait a Warm Device removes from every iteration.

Real phones, which is exactly where it counts. Physical hardware is the slowest thing to obtain and boot in mobile testing, so keeping real devices warm is where the time is won. Emulators benefit in the same way.

Run the Test Case once. The device that run used stays warm for your organization on the same Mobile App, Environment, device and language, so your next run claims it. Keeping your work on a consistent device and Environment is the single best way to stay warm.

Your editing. A Test Set's runs contribute their devices rather than claiming them, so the set leaves warm devices behind and the next run you start from the editor is the one that starts instantly.

Every run contributes. Scheduled runs, pipeline runs and background runs all leave their devices warm for your organization, so the first person to open a Test Case in the morning inherits capacity their suite already paid for.

The run starts a device the usual way, so a miss is never slower than before. The Device picker shows you which choice is warm beforehand, so you can pick a warm device when speed matters most.

Rely on the match, which is strict: a device holding your staging build is never used for a production run, and a device is only reused inside the organization it has already served.

Set App reset to Full reset or Fresh install. Either one opts the run out of Warm Devices, so it gets a device of its own, and it also keeps that run from leaving its device warm for anyone else. Reach for it when a flow must inherit nothing, for example when your Mobile App signs in from a device level account rather than storing its own session.

They come with an Enterprise plan. Speak to your Customer Success Manager if you already have one, or contact our sales team, and they will confirm what your plan covers. If you do not see the Warm badge anywhere in the Device picker, that is the first thing to check.