Safety, use and licence

Stillspin Strobe Tachometer · Revised 15 September 2026 · The same text is compiled into the app under More › Settings › Safety, privacy and terms

Flashing light

The app makes the screen and the camera torch flash rapidly. A flashing light between roughly 5 and 30 flashes a second can trigger a seizure in people with photosensitive epilepsy, including people who have never had one and do not know they are susceptible. Do not use it around anyone who has not agreed to it, and stop immediately if anyone feels unwell. The warning is shown before the app will run, and if Dim Flashing Lights is switched on in the iPhone's accessibility settings the app asks again before it flashes.

Moving machinery

A strobe makes a spinning machine appear to stand still. It has not stopped. Never put a hand, a tool, a sleeve or hair near anything you are measuring, and never treat a frozen picture as evidence that something is safe to touch.

What a reading can be relied on for

This is a hobbyist and workshop instrument, not a calibrated or certified one, and the measuring screens say so. Do not use it where a calibrated instrument is required. Do not rely on a reading where a wrong figure could hurt someone, damage a machine or cost money: setting a governor or a guard, deciding that something has stopped, certifying equipment, or calibrating another instrument for trade or commercial work.

The app measures rotation speed and reports its own ambiguity. It does not certify a machine, balance anything, or decide what a machine should be running at. Any target speed shown is a number you typed; the app ships no table of standard speeds and maintains no reference data. Its turntable screens are not wow and flutter meters or rumble meters, and say so.

The unlock

The download is free. A single unlock, bought once, adds the optical and acoustic methods, Compare, and the continuous turntable screen. The strobe and the freeze recorder are complete without it.

It is paid once through the App Store and does not renew or run out. Apple keeps the record of it with your Apple Account; the app only asks StoreKit on the device whether it is there, so deleting the app, or moving to a new iPhone on that Apple Account, costs nothing: Restore purchase reopens the routes. Apple takes the payment and handles refunds, and no payment detail reaches the app or the developer. Saved measurements stay readable whichever method took them, with or without the unlock.

If a reading is wrong

Using the app means following the safety parts of this page. Every reading is arithmetic on light, video or sound as this iPhone reports it, and none has been compared against a reference tachometer. The app is supplied as it is, with no promise that a reading is correct or that it suits a particular job.

As far as the law allows, the developer is not liable for injury, damage or loss that follows from using the app or from relying on a reading, including touching a machine because it looked still. Nothing here limits a liability the law does not let anyone limit, such as for death or personal injury caused by negligence, and nothing here takes away your statutory rights as a consumer.

Licence

No separate licence is written for this app. Using it is covered by the Licensed Application End User License Agreement that Apple publishes, which carries its own limits on warranty and liability alongside the ones above.

Who to write to

Aleksei Bukhalov makes this app: alex@bukhalov.com, with Stillspin in the subject line.