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Texting and SMS

How to text over wifi when you have no signal

Reviewed by Sujan ThapaliyaLast updated

The short answer

Messages sent through an app — iMessage, WhatsApp, a business texting platform — travel over data, so they work on wifi with no cell signal. Standard SMS between two ordinary handsets needs the carrier network, unless you enable wifi calling on the line, which carries SMS over wifi too.

There are two entirely different things people mean by texting, and they behave differently the moment signal drops. Sorting out which one you are using answers the question in about ten seconds.

Which messages travel over wifi?

The bubble colour on an iPhone is a reliable tell: blue is data, green is the carrier.
Type of messageTravels overWorks on wifi with no signal?
iMessage (blue bubbles)DataYes
WhatsApp, Signal, MessengerDataYes
Business texting platformInternet, via carrier APIsYes — the sender never uses a handset radio
SMS (green bubbles), wifi calling offMobile networkNo
SMS, wifi calling onWifi, then the mobile networkYes
MMS with a photoMobile data or wifi callingUsually, with wifi calling on

How do you turn on wifi calling?

  1. 1

    Check the carrier supports it

    Nearly all major carriers now do, on most plans. It is a line feature rather than a handset one, so a phone that offers the setting may still need it enabling on the account.
  2. 2

    Turn it on in settings

    iPhone: Settings, then Phone, then Wi-Fi Calling. Android: the Phone app's settings or the network settings, where the wording differs by manufacturer.
  3. 3

    Confirm the emergency address

    You will be asked for one. It is the address emergency services are given if you call from wifi with no cell signal, and it is worth getting right rather than skipping.
  4. 4

    Test it properly

    Put the phone in airplane mode, turn wifi back on, and send an SMS to another phone. If it sends, wifi calling is working; if it fails, the line setting has not taken.

Airplane mode plus wifi is the honest test

Testing in a weak-signal area proves nothing, because the phone may still be using the last bar of cell signal. Removing the radio entirely is the only way to know which path a message actually took.

Why does this matter for a business?

For a person, wifi texting is a convenience in a basement. For a business it is the difference between a channel that depends on where staff are standing and one that does not. A business texting platform sends through carrier APIs over the internet, so a message goes out identically from an office, a home desk or an airport.

What decides whether those messages arrive is not connectivity at all. It is registration and consent: application-to-person traffic has to be registered against a brand and a use case or carriers filter it, and the permission rules that govern calling a number govern texting it. Those are covered in business SMS and in our 10DLC guide.

One consequence worth planning for: a business number that receives replies needs somebody watching it. A platform number texting from an office and receiving into an inbox nobody opens is the messaging equivalent of an unanswered phone.

Frequently asked questions

Can you send a normal text message over wifi?
Only with wifi calling enabled on the line. Standard SMS is carried by the mobile network, so without wifi calling it needs signal. Anything sent through an app — iMessage, WhatsApp, a business texting platform — travels over data and works on wifi regardless.
How do I turn on wifi calling?
On iPhone it is in Settings under Phone; on Android it is usually under the Phone app's calling settings or the network settings, and the wording varies by manufacturer. Your carrier has to support it, and most now do. Once on, both calls and SMS route over wifi when signal is poor.
Why do my green-bubble texts fail on wifi but blue ones send?
Blue is iMessage, which travels over data. Green is SMS, which needs the carrier network. If one sends and the other does not, you have data but no usable cell signal — and wifi calling is what closes that gap.
Does texting over wifi cost anything?
App messages use data, which on wifi is free to you. SMS over wifi calling is billed exactly as a normal text under your plan — the route changed, not the product.
Can a business text customers over wifi?
Yes, and it is not really the same question. Business texting platforms send through carrier APIs over the internet, so the sender never depends on cell signal at all. What decides delivery there is registration and consent, not connectivity.

Sources

  1. Messaging Principles and Best Practices — CTIACarrier expectations for A2P messaging: 10DLC registration, opt-in and opt-out handling, and content rules.

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