What does **21* mean on my phone?

It's the GSM USSD code for unconditional call forwarding. Dialing `**21* #` tells your carrier to forward every incoming call to that destination immediately — your phone never rings. Used on AT&T wireless, T-Mobile, Cricket, Mint Mobile, and most international GSM carriers.

Will my phone ring at all after I dial **21*?

No. **21* is unconditional — every call routes to the destination immediately, and your phone stays silent until you cancel with ##21#. If you want your phone to still ring for the calls you can pick up, use **61* (conditional forwarding) instead.

Does **21* work on iPhone and Android?

Yes — USSD codes are a carrier feature, not a phone feature, so the same code works on any iPhone or Android phone on a GSM carrier. Dial in the regular Phone app and press the green call button. On Verizon legacy CDMA, use *72 instead.

How do I check if **21* forwarding is on?

Dial `*#21#` and press call. The carrier returns a popup showing whether unconditional forwarding is active and what number it routes to. `*#21#` is read-only — it doesn't change anything.

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What does **21* and ##21# mean?

Q: What does ##21# mean?

##21# cancels the unconditional call forwarding rule (the `**21*` setting). Dial it from the same line that has forwarding active, press the call button, and inbound calls ring your phone normally again.

**21* sets unconditional call forwarding. ##21# cancels it. Two codes, one feature, every GSM carrier.

`21*<number>#

** is the GSM USSD code that tells your carrier to **forward every call** to a destination number — also called unconditional forwarding. **

##21#

** is the cancel: it turns that forwarding off. Both codes work on every GSM wireless carrier (AT&T wireless, T-Mobile, Cricket, Mint, Vodafone, EE, O2, Rogers, and most international networks). They don't work on landlines or CDMA carriers — those use

*72 and *73` instead.

**21* — forward every call

`21*<number>#` is the GSM USSD code for unconditional call forwarding**. Dial it followed by a destination phone number, press the green call button, and from that moment every incoming call to your line routes immediately to the destination — your phone never rings.

Example: **21*18005551234# forwards every call to 1 (800) 555-1234.

Breakdown of the code: - ** — USSD prefix that activates a network service with parameters. - 21 — the GSM code for unconditional forwarding. - *<number> — the destination phone number, with no spaces or dashes. - # — terminates the USSD string (without it, the phone places a regular call).

After dialing, your carrier confirms with a popup or text. From that point, your phone stays silent for incoming calls until you cancel with ##21#.

##21# — cancel unconditional forwarding

`##21#` turns off the **21* rule. Dial it from the same line that has forwarding active, press the call button, and the carrier confirms cancellation. Incoming calls then ring your phone normally again.

##21# only cancels unconditional forwarding (the **21* rule). If you've also set conditional forwarding (**61*), use ##61# to cancel that one separately. To wipe every forwarding rule at once — unconditional, busy, no-answer, unreachable — dial ##002#.

The full GSM forwarding family

**21* and ##21# are part of a four-condition family of GSM forwarding codes — one set per condition:

Condition	Set code	Cancel code	Query code
Always (unconditional)	`*21<number>#`	`##21#`	`*#21#`
When busy	`*67<number>#`	`##67#`	`*#67#`
When unanswered	`*61<number>#`	`##61#`	`*#61#`
When unreachable	`*62<number>#`	`##62#`	`*#62#`
All at once	—	`##002#`	—

Most carriers conflate "busy" and "unanswered" into the single **61* conditional rule — handier for everyday use because one code covers both. The query codes (*#21#, *#61#, etc.) return the current forwarding target without changing anything — useful if you suspect forwarding was left on but don't know where calls are going.

Which carriers use **21* and ##21#

Every GSM wireless carrier: - US: AT&T wireless, T-Mobile, Cricket, Mint Mobile, Boost (GSM mode), Ultra Mobile, US Mobile (T-Mobile network), Google Fi (T-Mobile), most other GSM MVNOs. - UK: Vodafone, EE, O2, Three, Tesco Mobile, giffgaff, BT Mobile. - Canada: Rogers, Freedom Mobile, Public Mobile, Chatr, Fido. - Australia: Telstra, Optus, Vodafone AU. - International: most networks worldwide.

They don't work on Verizon legacy CDMA, US Cellular CDMA, landlines, or cable VoIP (Spectrum, Comcast Xfinity Voice, Cox) — those carriers use the older *72 / *73 star codes for the same feature.

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FAQ

What does **21* mean on my phone?: It's the GSM USSD code for unconditional call forwarding. Dialing **21*<destination-number># tells your carrier to forward every incoming call to that destination immediately — your phone never rings. Used on AT&T wireless, T-Mobile, Cricket, Mint Mobile, and most international GSM carriers.
What does ##21# mean?: ##21# cancels the unconditional call forwarding rule (the **21* setting). Dial it from the same line that has forwarding active, press the call button, and inbound calls ring your phone normally again.
Will my phone ring at all after I dial **21*?: No. **21* is unconditional — every call routes to the destination immediately, and your phone stays silent until you cancel with ##21#. If you want your phone to still ring for the calls you can pick up, use **61* (conditional forwarding) instead.
Does **21* work on iPhone and Android?: Yes — USSD codes are a carrier feature, not a phone feature, so the same code works on any iPhone or Android phone on a GSM carrier. Dial in the regular Phone app and press the green call button. On Verizon legacy CDMA, use *72 instead.
How do I check if **21* forwarding is on?: Dial *#21# and press call. The carrier returns a popup showing whether unconditional forwarding is active and what number it routes to. *#21# is read-only — it doesn't change anything.

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