iPhone Hidden Codes & Field Test Mode Explained (2026 Guide)
iPhone hidden codes explained: *#06#, Field Test Mode *3001#12345#*, call forwarding *#21#, call waiting *#43# and caller ID *#30# — what each shows and when it works.
iSerial TeamUpdated · 4 min read
In this article
Apple doesn’t hide a factory test menu behind the dialer the way Android makers do. What the iPhone does support is a small set of standard network codes — understood by the cellular network rather than by iOS — plus one genuinely hidden app: Field Test Mode, which shows raw radio measurements Apple never puts in Settings.
Used together, these codes answer practical questions: what is this iPhone’s real IMEI, how strong is the signal actually, is someone silently forwarding my calls, and is call waiting on? Here’s what each code does, what the result means, and why some of them depend entirely on your carrier.
Why iPhone codes behave differently from Android
Most iPhone codes are MMI / supplementary service codes from the GSM standards. When you dial them, the iPhone sends a request to your carrier’s network and displays the answer. That has two consequences:
- They need service. With no SIM or no signal, network codes fail or show an error.
*#06#and Field Test are the exceptions — they’re handled on the phone. - They vary by carrier. Some carriers, especially networks with CDMA heritage such as Verizon in the US, use their own star codes (for example
*72/*73for forwarding) and may ignore the GSM versions. A “Setting Interrogation Failed” message usually means the carrier doesn’t support that query, not that something is wrong.
Type every code in the Phone app’s keypad. Network codes run when you press the green Call button; *#06# appears as soon as you finish typing.
*#06# — IMEI, EID and more
*#06#Shows the IMEI (two on dual-SIM / eSIM iPhones), the EID for eSIM, and on some models the MEID. Compare it with Settings › General › About and, on models with a physical SIM tray, the number engraved on the tray. All three must match — a mismatch is a classic sign of swapped parts. Our IMEI finding guide lists every location.
Once you have the number, a free All-in-one check confirms the model, color, storage and Find My status, and the iPhone activation check confirms the device record.
Field Test Mode: *3001#12345#*
*3001#12345#*Type the code and press Call. The Field Test app opens with a dashboard of radio information. The layout changed in iOS 15 and differs between iPhones with Intel and Qualcomm modems, so labels may not match exactly, but the key numbers are there on current iOS versions.
Finding the signal strength
On an LTE connection, open the menu and look for LTE › Serving Cell Meas (or a similar serving-cell entry). On 5G, look for an NR section. The values that matter:
| Value | What it measures | Rough guide |
|---|---|---|
RSRP (e.g. rsrp0) | Received power of the cell’s reference signal, in dBm | −80 or higher excellent · −90 to −100 good · −100 to −110 fair · below −110 weak |
| RSRQ | Signal quality relative to interference | −10 or higher good · below −15 poor |
| SINR | Signal-to-noise ratio, in dB | above 13 good · 0 to 13 fair · below 0 poor |
Bars on the status bar are Apple’s rounded interpretation; RSRP is the real number. These ranges are rules of thumb — what counts as usable depends on the band and the network.
Why this matters for a used iPhone
Stand next to your own phone on the same network and compare RSRP. A gap of 15–20 dB on the same band points to antenna damage, a poorly reassembled phone, or a third-party housing. That’s a fault no seller will mention and Settings won’t show. Field Test also tells you the serving band, useful if an imported iPhone shows “No Service” — see unlocked but no service.
Call forwarding check: *#21# and friends
*#21#
*#61#
*#62#
*#67#These ask the network whether your calls are being forwarded:
*#21#— unconditional forwarding (all calls).*#61#— forwarding when you don’t answer.*#62#— forwarding when the phone is unreachable or off.*#67#— forwarding when you’re busy.
A result like “Voice Call Forwarding: Disabled” is what you want for *#21#. The conditional ones normally show your carrier’s voicemail number — that’s how voicemail works and is fine. A forwarding target you don’t recognize is not.
Why care? Silent call forwarding is a known step in account-takeover fraud: a criminal forwards your calls so verification calls reach them. Read more in our SIM swap fraud guide. On GSM carriers you can also review it in Settings › Phone › Call Forwarding. Many GSM networks accept ##002# to cancel all forwarding, but support varies — if in doubt, ask your carrier.
Call waiting and caller ID: *#43#, *#30#, *#31#
*#43#
*#30#
*#31#*#43#— is call waiting active? If it’s disabled, a second caller hears busy or goes to voicemail. You can also toggle it in Settings › Phone › Call Waiting on supported carriers.*#30#— CLIP: whether the network shows you the caller’s number on incoming calls.*#31#— CLIR: whether your number is hidden on outgoing calls. The iPhone equivalent is Settings › Phone › Show My Caller ID.
These are the codes to try when a phone “doesn’t show who’s calling” or “sends everyone to voicemail”. They report network settings for your line, not faults in the phone.
What codes can’t tell you — and what to check instead
There’s no dialer code that shows whether an iPhone is carrier-locked, blacklisted or still linked to someone’s Apple ID. For the lock, look at Settings › General › About › Carrier Lock: “No SIM restrictions” means unlocked. Our guide to checking if an iPhone is unlocked covers the edge cases. For the record-level picture:
- Carrier + SIM-lock check — which network the iPhone is locked to.
- GSMA blacklist check — lost or stolen reports worldwide; for US phones, the USA blacklist / barred check.
- iPhone warranty check — coverage and an estimate of when it was sold.
Try it in the terminal: type dial to see every IMEI code, imei followed by a 15-digit number to validate it, or tac with the first 8 digits to identify the model:
For network locks, see our iPhone unlock guide.
Verdict: four codes earn a place in your memory — *#06# for identity, *3001#12345#* for real signal strength, *#21# for hidden forwarding and *#43# for call waiting. Everything else about an iPhone’s history lives in its IMEI record.
Frequently asked questions
How do I open Field Test Mode on iPhone?
Open the Phone app keypad, type *3001#12345#* and press Call. The Field Test app opens with signal details such as RSRP, RSRQ and SINR.
What is a good RSRP value on iPhone?
Around −80 dBm or higher is excellent, −90 to −100 dBm is good, and below −110 dBm is weak. Exact thresholds depend on band and network.
How do I check if my iPhone calls are being forwarded?
Dial *#21# and press Call. “Disabled” means calls aren’t forwarded unconditionally. Some carriers, such as Verizon, use their own codes instead.
Why does an iPhone code say Setting Interrogation Failed?
Your carrier doesn’t support that network query, or the phone has no service. It doesn’t mean the phone is faulty.
Is there a code to check if an iPhone is unlocked?
No. Check Settings › General › About › Carrier Lock, or run a carrier and SIM-lock check on the IMEI.
