Periphery How to find a lost Bluetooth device with your iPhone by signal strength
If the device still has power and is advertising over Bluetooth Low Energy, you find it by walking toward a stronger signal. Scan with Periphery, tap Locate on the device, and follow the gauge from Freezing up to Very Hot!. No map, no arrow. Just warmer or colder, which is all signal strength can tell any phone, ever.
Can you find a lost Bluetooth device at all?
Yes, if two things hold: the device still has battery, and it is advertising, meaning it keeps sending out the short radio packets that let phones discover it. Most trackers, tags, fitness bands and plenty of earbuds do exactly this whenever they are on and not already connected to something else.
Switched off, flat, or stuck in a closed charging case that blocks advertising, and no app on earth hears it, Periphery included. It also only sees Bluetooth Low Energy. Classic-only gear stays invisible to every scanner on the App Store, not just this one.
How to track a lost Bluetooth device with Periphery
- Go to the room or area where you last had the device and open Periphery.
- Tap Scan. Set Sort by to Strongest signal so the nearest devices rise to the top.
- Look for the device's name. If you are not sure, type part of it in Filter by name or UUID.
- Swipe the row left and tap Locate, or tap the location icon on the row.
- Walk slowly in one direction for a few steps and watch the subtitle: Getting warmer… means keep going, Getting colder… means turn back.
- Follow the haptic pulses. They come faster as the signal gets stronger. When the status reads Very Hot!, search the spot within arm's reach: under cushions, in bags, down the side of seats.
What the Locate screen shows
- The live signal in dBm. Closer to 0 is stronger: -55 dBm is much stronger than -85 dBm.
- A gauge that fills from empty at -95 dBm to full at -40 dBm.
- A status: Freezing, Getting Closer, Warm or Very Hot!. If the device has not been heard for 4 seconds, it shows Signal Lost; move around to pick it up again.
- A rough distance under the gauge, marked approximate distance, in metres or feet depending on your iPhone's region.
Worked example: from signal to distance
Periphery estimates distance with the log-distance path-loss formula: distance = 10 ^ ((-59 - RSSI) / 20) metres, which assumes a typical device reads -59 dBm at 1 metre. The status switches at about -81 dBm (to Getting Closer), -65 dBm (to Warm) and -51 dBm (to Very Hot!).
| Signal | Distance (metric) | Distance (US) | Status |
|---|---|---|---|
| -59 dBm | ~1.0 m | ~3.3 ft | Warm |
| -65 dBm | ~2.0 m | ~6.5 ft | Getting Closer |
| -70 dBm | ~3.5 m | ~11.6 ft | Getting Closer |
| -75 dBm | ~6.3 m | ~20.7 ft | Getting Closer |
| -80 dBm | ~11.2 m | ~36.8 ft | Getting Closer |
| -86 dBm | ~22.4 m | ~73.4 ft | Freezing |
| -90 dBm | ~35.5 m | ~116.4 ft | Freezing |
So if you start at -80 dBm, the estimate says about 11 m and the status reads Getting Closer. By the time you reach -59 dBm, it says about 1 m and the status has turned Warm.
Tips that make the search faster
- Hold the phone the same way the whole time. Turning it or covering it with your hand changes the reading.
- If several devices share the same name, note the short identifier under the name so you track the right one.
- If earbuds do not show up, the case may be closed. Try when you think they might be out of the case, or ask someone to open any case you find.
What Periphery cannot do
It will not show where a device was last seen. It cannot find anything out of Bluetooth range, usually tens of metres at most indoors, and it cannot make a device chirp or play a sound. No GPS, no location request, ever. This is a signal-strength finder for when you are already in the same room, nothing further.
One honest limit: Locate only works on the scan you already have running, and the free version caps you at 3 scans in total, for good. If your lost item is a repeat offender, that count disappears fast.
Questions and answers
Can Periphery find earbuds that are in their case?
Does Locate point me in a direction?
How close does Very Hot! mean?
Why does it say Signal Lost?
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- How to read, write and subscribe to a BLE characteristic from your iPhone
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