When does Messages message via iMessage vs. SMS?

Question

This is probably an embarrassingly noobish question.

I sent a standard SMS text message from my iPhone 6 to a colleague's iPhone, who mentioned that my message was green and not blue, and that meant I hadn't activated something or wasn't using the right app to take advantage of iMessaging.

Currently I don't use apps beyond what came with my phone. To send SMS text messages I use the green callout balloon button that's near the phone button.

My colleague said I could save money by using iMessage instead of paying for each SMS text message. I countered by saying that if it's not SMS then that means I'd have to keep my phone connected to the internet 24/7 to receive messages and I don't do that.

My colleague then said something like it does but doesn't use SMS, so I wouldn't have to maintain an internet connection 24/7 to receive prompt iMessages and yet would not have to pay for SMS messages when I did.

A quick search turns up plenty of tutorials about how to use iMessages but so far I have not found a clear and concise explanation.

Is it possible to explain in a few clear sentences how the messaging functionality works on my iPhone 6 and when internet is used and when traditional SMS messages are used? For example:

• Does it check first for an active internet connection on the sender's phone?
• Does it also check if the recipient is also connected to the internet?
• Could a message go out as an iMessage and then not be delivered even though the recipient could have received an SMS text message?

Answer 1

To send SMS text messages I use the green callout balloon button that's near the phone button.

You are using the correct app.

My colleague said I could save money by using iMessage instead of paying for each SMS text message.

Your colleague is absolutely right. At least in this context. iMessage is Apple's Internet messaging service. You can send an iMessage to anyone who has an Apple device (such as iPhone, iPod Touch, iPad, Apple Watch, Mac desktop or laptop computer etc.). The requirements is that the recipient must have registered their Apple ID with iMessage service and enabled iMessage. Either of email address (Apple ID) or mobile number (associated with your iPhone) can be registered with iMessage and can be used as sending destination.

The same Messages app is used for sending both an iMessage and SMS to contacts and recipients. An SMS is identified with a green bubble while an iMessage is identified with a blue bubble.

Additionally, you need not remain online all the time for iMessage to work, if either the sender of receiver is offline (not connected to the Internet), the sent message gets stored on device or Apple's servers respectively, and dispatched as soon as the Internet connectivity is restored (either via Mobile Data or Wi-Fi). It in a way works for how email works. Unlike some other messaging app, there's no concept of user being "online" or "offline" in iMessage.

When the recipient is either using a non iPhone phone or they don't have their number registered with iMessage service, your text message gets sent as a plain SMS, and all the same restrictions apply (character count, carrier charges). However, iMessage allows you to send text messages, media such as photos and videos and with iMessage apps stickers etc.

It's important to note that iMessage is a service available free of cost and is exclusive to Apple ecosystem of devices.

You can force an iMessage to be sent as a plain SMS if you suspect the recipient may have their Internet connection (Mobile Data or Wi-Fi) turned off, and you want the message to get across as quickly as possible (as an SMS is sent over cellular network).

Is it possible to explain in a few clear sentences how the messaging functionality works on my iPhone6 and when internet is used and when traditional SMS messages are used?

Answers below inline:

Does it check first for an active internet connection on the sender's phone?

No. Sending iMessage has nothing to do with active connection on recipients end.

Does it also check if the recipient is also connected to the internet?

No. The recipient gets the message whenever they turn on Internet on their device. The messages you sent are held on Apple's computers in the meanwhile.

Could a message go out as an iMessage and then not be delivered even though the recipient could have received an SMS text message?

If a message is sent out as iMessage, it will indeed get delivered (as long as their number is registered with the iMessage service) when the recipient turns on Internet on their device.

P.S.: I can direct you to this excellent document online officially maintained by Apple, which explains iMessage service and it's features in an easy to understand way.

Messages for iPhone, iPad, Apple Watch, and Mac

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Force Messages app to send a text message as SMS instead of an iMessage

Here's a workaround that you can use to force the Messages app to send a test message as SMS instead of iMessage to a contact's phone number. It is slight clumsy, but gets the job done in the scenarios like you described:

1. If you have Internet access available on your iPhone via either Mobile data or Wi-Fi (indicated by the presence of appropriate icon in the iPhone's status bar), and the receivers contact number is registered with iMessage, you'll only be able to send an iMessage, irrespective of the online/offline status of the recipient. You can check if a message would be sent as an iMessage by the presence of a blue colored upward facing arrow besides your typed text message.

   

2. To force the message to be sent as SMS instead, temporarily turn off Mobile Data/Wi-Fi on your iPhone to disable Internet access. You'll still only be able to send an iMessage (Blue arrow icon) as your iPhone knows that the receiver is registered with iMessage. Send the message normally.

   The message won't get sent from your iPhone due to the absence of an Internet connection. Now tap an hold on the message bubble, and you'll see an alert at the bottom of the screen with an option that says Send as Text Message. This option is not shown when you have Internet connectivity on your iPhone, or the message is already delivered to the Apple's servers.

   

3. This will cause your iPhone to re-send the message as SMS. The receiver will be able to get the message even in absence of the Internet connection on their device (as long as they have cellular connectivity on their device).

4. Don't forget to turn Mobile Data/Wi-Fi back on on your device to regain access to Internet.

Answer 2

I know this is an old thread, but I agree with pkamb's answer. SMS uses the cellular control channels to carry messages. iMessage uses IP (internet protocol=mobile data). That means that SMS is available as long as you have cellular service, and iMessage protocol is available as long as you have internet service. The majority of users have unlimited data plans, and are always connected to the internet, which means if they have a signal, they have both SMS and iMessage services. The exception would be people who have really small data packages and turn off their mobile data to save money. In that case iMessage would automatically fall back to SMS without you needing to do anything on either end. So the automatic fallback to SMS means that there is no disadvantage to using iMessage protocol, as your message will get through, unless the receiving phone has no signal, or is off. And in that case, I find iMessage is better at buffering messages than SMS.

Answer 3

uhoh stated, "what I don't understand is how Apple mixes access to the two totally different services SMS and iMessage in the same window, and how to know ahead of time if, for a given contact, a message is going to go out as SMS or iMessage"

iMessage requires both the sender and receiver's iPhones to be logged into iCloud with appleid's. This allows apple to see them both and know when the iMessage protocol can be used. If either account gets logged out, or otherwise disabled, maybe due to mobile data being turned off, the conversation is switched to SMS, on the fly. I have had some of my conversations switch from blue to green, and eventually back to blue, because of service issues on the other end. I believe this automatic functionality, along with delivery and read receipts, makes iMessage the superior choice over standard SMS only apps.

P.S. I have searched, and cannot find a way to determine which protocol is going to be used, when you hit the send button. I do know that if it thinks that it can use iMessage protocol, the send button is blue. But I have had messages turn green after I hit send, apparently because the lack of an iCloud connection at the other end had only registered after message transmission.

Answer 4

iMessages are sent via the internet (cellular data or Wi-Fi).

SMS messages are sent only via cellular service.

iPhones should generally have cellular data service any time they have "phone" service. So when you can send an SMS, you should also generally be able to send an iMessage. And same for your recipient immediately receiving them.

(This of course depends on your phone plans and specific coverage/network issues.)

This is a perfect use-case for SMS; if their phone is turned on, they'll almost certainly get it within a few minutes. But if we've started to use iMessage then they won't get it until they go home and connect to the internet because I've essentially e-mailed it to them. Have I got the basic idea correct?

You do not need to be connected to your home Wi-Fi network in order to send iMessages. They are also sent and received via a cellular data plan, on the go, just as conveniently and reliably as SMS.

iMessage is also especially good when you do not have cellular service. If you're ever able to connect to Wi-Fi, you can send and receive iMessages. But not SMS messages, until you get back to cell coverage. This makes iMessage far more reliable for contacting people who live in spotty cell coverage areas.

iMessage offers huge benefits over SMS: cost, encrypted security, messaging features, reception without cellular service, significantly better group messaging, etc.

Unless there is a specific reason you or your recipient will not have data service on the go, you should use iMessage. The app will fall back to SMS if needed.