Use this clever trick to see your iPhone's true signal strength
Ever find yourself questioning how accurate those little signal strength dots are on your iPhone?
Luckily, there's a trick to reveal your iPhone's true signal strength, and it takes less than a minute to enable.
First, you'll need to access a hidden app on your phone called Field Test Mode. To do this, you'll need to open up your Phone app and dial the following number, *3001#12345#* , including the asterisks and hashtag, and tap "Call."
This opens up Field Test Mode, which is mostly filled with menus of cell signal jargon that you don't need to worry about. What you're interested in is the tiny number in the upper left-hand corner of your iPhone - likely hidden behind the text "Back to Phone" if you're using iOS 8 or iOS 9 - which is your iPhone's true signal strength.
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Here, for example, my old iPhone 5 that's still running iOS 7 is showing my cell signal to be -59. To exit Field Test Mode, you can simply tap the home button and you'll be brought back to your iPhone's home screen, no harm done.
While that number can vary anywhere from -40 to -130, it will always be negative, and the closer that number is to zero, the better your cell signal, according to OSX Daily. The best signal you can get would be -40, and no signal at all would be -130.
If your iPhone is running iOS 8 or iOS 9 and you can't see the number because of Apple's new "Back-to-last-app" feature that creates a link to the last app you were using in the same corner of your screen, don't worry. There's still another way to display your true signal strength. This method allows you to always have easy access to that number without going through the hassle of dialing out to the Field Test App, enabling your iPhone to display both numbers so you just tap the signal dots in the future to check.
To enable this, return to your phone and dial *3001#12345#* and tap "Call," like before.
You'll be brought to the Field Test App again, but instead of using the home button to exit, hold down your iPhone's power/sleep button until it shows the "Slide to power off" screen and then hold the down your iPhone's home button, which will force quit Field Test App.
You'll be back to your iPhone's homescreen, but this time you should notice that your signal strength number has replaced your signal strength dots.
If you tap that number, you can switch between the two as you see fit.
To undo any changes you made, simply repeat the steps to get into Field Test Mode and tap the Home button to exit the app, and everything will revert back to normal.
