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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.

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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?
pkamb
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uhoh
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  • SMS are delivered even if your phone is offline for a while as well :-) Anyway, have you signed up for iCloud and configured iMessage accordingly? – nohillside Nov 23 '19 at 07:06
  • @nohillside I know how SMS works, but it's the way Apple's app has mixed together two totally different messaging services with different connectivity dependences and sources of latency that's had me confused. I think that once I start with the iMessaging to a given contact I'll never be able to force a fast SMS to the same contact. So I'm going to avoid the app because I like the way SMS messages tend to get there within a minute or two as long as the recipient's phone on and not in airplane mode. – uhoh Nov 23 '19 at 07:17
  • @nohillside I mean I'm going to avoid ever letting the app start sending iMessages because I like the way SMS works, and if I start allowing iMessaging then (if I understand correctly) I won't be able to force an SMS. That may be best addressed as a separate question. If I can't find that it's been asked already, I'll ask "How can I force an SMS in messages?" update: that's been asked several times, okay I'll read those. – uhoh Nov 23 '19 at 07:34
  • iMessages get there within seconds as well, as long as both parties are online. – nohillside Nov 23 '19 at 10:05
  • @nohillside ...and don't if either of them isn't. – uhoh Nov 23 '19 at 10:32
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    As with SMS actually :-) – nohillside Nov 23 '19 at 10:39
  • @nohillside it is not symmetrical. You don't usually have a phone turned OFF or in Airplane mode still using iMessage (though I suppose you could if you took out the SIM card or didn't pay your phone bill). But there are a million iPhones turned on right now that can exchange SMS but are not connected to the internet. – uhoh Nov 23 '19 at 10:41

4 Answers4

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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

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.

Nimesh Neema
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    Thank you for your speedy answer! Hypothetical: I need to send the message "Go home, don't wait for me; I've changed plans" to a contact in my messages app. 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? – uhoh Nov 23 '19 at 07:06
  • "You can force an iMessage to be sent as a plain SMS..." I've found a lot of activity in this site related to forcing SMS but I haven't found a definitive answer that's recent, and some answers specify very old versions. I can ask "How to force Messages to send the current message via SMS? (iOS12)" separately, unless you'd like to add a link or address that here. – uhoh Nov 23 '19 at 08:31
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    @uhoh Your assumption is correct in so far as SMS are transferred via cellular/phone connections, iMessages are transferred via data connections. So yes, if either you or the recipient don't have mobile data the message won't get through until you (to send it) and afterwards the recipient (to receive it) have internet connection. – nohillside Nov 23 '19 at 10:02
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    Nimesh, can you post the answer to "You can force an iMessage to be sent as a plain SMS" to https://apple.stackexchange.com/questions/260035/force-outgoing-sms-instead-of-imessage-from-an-iphone-6s-to-a-specific-contact please? – nohillside Nov 23 '19 at 10:04
  • @uhoh You have the basic idea absolutely right. I encounter the same case every now and then. I have updated the to share a workaround that I use in scenarios like the one you described. It's slightly clumsy, but certainly a lifesaver. – Nimesh Neema Nov 24 '19 at 13:43
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    Thank you very much for the edit, this is what I need to know! Ideally my question How can I ensure or force a message I'm composing to go via SMS on my iPhone 6 in iOS 12? would not have been insta-closed and you could have posted that part as an exact answer there. If it's reopened perhaps you can think about adding or moving this there. In any event, I really appreciate your additional help! – uhoh Nov 24 '19 at 14:50
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    @uhoh You are welcome. I have added an answer to the linked duplicate to your post. – Nimesh Neema Nov 24 '19 at 15:34
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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.

Leonard
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  • Thanks for your opinion and Welcome to Apple SE!! The question does say "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." It was an iPhone6 with an ailing/dying battery and the original iOS that came with it, and connecting to the internet seemed to drain it substantially faster. I'm told that this is not the case for more modern iPhones and iOS versions which manage power usage even more effectively. – uhoh Jun 12 '22 at 11:11
  • There could conceivably be other reasons to prefer messages go using one service over the other, but for simply performance and convenience reasons it seems leaving everything on and letting the phone worry about it is best for most people. – uhoh Jun 12 '22 at 11:12
  • "that means I'd have to keep my phone connected to the internet 24/7 to receive messages" is an incorrect assumption. One could simply toggle mobile data to receive any queued messages. Then toggle again to save battery. 24/7 connections are not necessary to receive messages. Plus Apple offers a return receipt function, that allows you to see if your message was delivered, and/or read, SMS protocol has no such functionality. Turning off your cellular service can cause you to miss SMS messages, depending on your carrier, and the sender would not know. – Leonard Jul 15 '22 at 20:24
  • Okay, if I remembered to toggle mobile data on my (then) iPhone 6 on for say 30 seconds every 15 minutes, then I would get my iMessages within 15 minutes. That's unattractive but feasible. But SMS is a lot simpler so I don't think it's an argument in favor of iMessage. I now have an iPhone SE 2 which I am told manages power better, and occasionally notice that some people receive my text messages via iMessage and I'm okay with it :-) – uhoh Jul 15 '22 at 23:05
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    You could experiment to see if leaving mobile data on significantly affects your battery life. It may not be that much. – Leonard Jul 17 '22 at 09:02
  • When I asked this question in 2019 I had an iPhone 6 with a dying battery. I have a much newer phone and I have heard the power management is much better, so I think this is pretty much moot now. Thanks! – uhoh Jul 17 '22 at 09:21
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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.

Leonard
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  • Interesting! When I send a text message to some people, I see it goes via iMessage (it's blue and I see the "received" indicator). That means my iPhone is logged into to iCloud? Hmm... I don't recall ever doing that, though when I bought my apple Watch they made me do a bunch of things (including update my phone's OS) before they could get my phone and watch to tether, so maybe it was then. You are certain my phone must be logged in to iCloud for this to happen? Can you cite a source saying so? Thanks! – uhoh Jul 15 '22 at 23:13
  • I apologize, it seems I was misinformed. iCloud login is not necessary to use iMessage. (I thought I had experimentally confirmed that, but I think it was because of the differences in the macOS iMessage app, and the phone number/email setup I was using at the time). I found this page, which explains the method Apple uses for setting up iMessage services. Interestingly, it says Apple sends SMS messages to from your iphone to their servers for provisioning https://www.ilounge.com/index.php/articles/comments/the-complete-guide-to-facetime-imessage-set-up-use-and-troubleshooting/ – Leonard Jul 17 '22 at 08:43
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    So, the article says that you can configure iMessage on your iPhone with just your number, but that activation requires SMS via cellular service. And that an Apple ID is needed to use those services on other devices. – Leonard Jul 17 '22 at 08:56
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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.

Community
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pkamb
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  • Thanks for your answer. I understand (somewhat) how all the connections work on my phone (voice, SMS, data/4G, WiFi, etc.) but 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. See this comment. – uhoh Nov 23 '19 at 07:21
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    My concern is not with the sending of the message, it is with the recipient getting it in a timely fashion. If they don't have internet connectivity, an SMS will still get there just the same. But if my phone decides to send the message as an iMessage then they won't get it until such time as they reconnect to the internet. So I need to understand better how my phone chooses between sending it by SMS, or by iMessage. – uhoh Nov 23 '19 at 07:27
  • @uhoh Most iMessage recipients never think about "connecting to the internet"... they just get their messages immediately via a data plan. In most cases where they don't receive iMessages they wouldn't be getting SMS either. If you have unique data plan / coverage issue requirements you should edit those into the question. – pkamb Nov 23 '19 at 07:41
  • I've asked the question to which I'm interested in an answer. "When does Messages message via iMessage vs. SMS?" I've explained why I want to know the answer to that question. It has to do with the recipient receiving the message in a timely fashion if they are not connected to the internet. "Most people are always connected to the internet" is not an answer; it's a non sequitur. – uhoh Nov 23 '19 at 07:59
  • @pkamb In most cases where they don't receive iMessages they wouldn't be getting SMS either. No, if I have turned off Mobile data, I can happily receive sms. – Andra Nov 23 '19 at 17:24
  • @Andra "my recipients might have mobile data off, therefore I should always send every message as SMS" is IMO not a very compelling strategy. Your recipient will just be annoyed to get green bubble texts, like the colleague in the OP. – pkamb Nov 23 '19 at 17:42