A read receipt is essentially a small message that is sent between phones to indicate when someone has opened up your text thread, and most likely read a text message that you sent. It's a very helpful little feature that allows you to know when your message has actually been read, as opposed to just delivered.
In iOS, with read receipts enabled (Settings -> Messages -> Send Read Receipts), the "Delivered" text that a person sees under an iMessage they have sent you turns to "Read" when you've viewed it in the conversation thread, so they know you've seen the message even if you've not responded.
And remember, if the message says "read" but has no timestamp, the other person probably has read receipts turned off.
Read tells you that the recipient opened it. You don't see the read receipts if you've been blocked or the message was sent over SMS. That makes this a great way to tell if those green text bubbles mean someone blocked you or switched to Android because messages can still be marked as read on Android.
Read Receipts on Android Smartphones
The Google Messages app supports read receipts, but the carrier must also support this feature. Your recipient must have read receipts activated for you to see if they read your message.
According to dating coach James Preece, read receipts can give rise to a number of problems in relationships because they amplify mismatches in communication preferences. “One person might assume that by purposefully not replying, you are hiding something or keeping secrets," he told The Independent.
Read means the user that you sent the message to actually opened up the iMessage app. If it says delivered, they most likely didn't look at the message although it was sent through. You can change it though in Settings to make it that you don't send a read receipt when you read a message.
A red flag that you've been blocked is when you don't see the delivery status or the read receipt at all. The message you just sent will still be in a blue bubble, but it will have no delivery status below it – not even a "Not Delivered."
Read receipts tell people when you have viewed an incoming message, which can be helpful when you don't want to keep the other person in suspense wondering if you've seen their text. The feature is built into Apple's Messages app but is not available for regular SMS texts.
If you send a message as a regular SMS in the green text bubble and you do not get a “Delivered” notification but instead get a notification similar to “Message not Delivered” or no message at all, that means you were probably blocked.
In Messages (is the app, iMessages a type of message in Messages app), why does it say 'read' even though the other person hasn't read the message yet? Because the receiver has the Messages app open to your thread.
What does left on read mean? In internet slang, a person is left on read when a recipient has read, but not responded to, a sender's message. The expression is often used to express feeling ignored.
Instead of beating yourself up or getting upset because you didn't receive an immediate response, think positively. However, if your message is left on read for more than eight hours, then it might be time to start panicking. Article continues after video.
Check the Bubble Color
If you don't see a blue bubble on your end, then it's likely that they've blocked you on iMessage. It's important to note that this doesn't mean they have blocked your number altogether; it just means they have blocked you from sending them messages over iMessage.
"Delivered" means the message has been successfully received by the person's iPhone, but not necessarily that it has been opened. If Read Receipts are on, it will show the time the message was read. If Read Receipts are off, it will say "Delivered" regardless if they have read it or not.
When you Ignore a chat thread, even though you will receive all the messages, the Messenger will mark them as Sent only and not Delivered. You will see a hollow blue circle with a checkmark inside to indicate Sent, and a filled-in blue circle shows it as Delivered.
On an Android
Like iPhone users, Android read receipts require both sender and recipient to enable the feature. Instructions may vary according to your device's manufacturer, model, and operating system.
On an iPhone, Apple's Messages app lets you know if your recipient has read your message — but the sender and recipient must be using iMessages on an iPhone or iPad, too, and have read receipts enabled. To turn this on, open Settings, tap Messages and enable Send Read Receipts by flipping the switch so it is green.
When you block a phone number or contact, they can still leave a voicemail, but you won't get a notification. Messages that are sent or received won't be delivered. Also, the contact won't get a notification that the call or message was blocked.
While someone is blocked, any sent text messages will be blocked by Messages. You won't be able to retrieve them. If you decide to unblock the person, you will receive the texts normally. However, if the blocked person calls and leaves you a voicemail, you can check it.
Look for the checkmarks: A single gray checkmark indicates a successfully sent message. The appearance of a second gray checkmark shows your message was delivered to the recipient's phone. The two checkmarks will turn blue if the recipient has viewed your message.
Perhaps your friend is being busy at that moment and just forgot to respond at the moment. People are not obligated to reply to one's message after reading it. If you do really are concern, you should take initiative and ask them about it. A simple message as a reminder for them will do.
Message Read Receipts on Android
You can turn it on in your messaging app Settings. Click directly on Multimedia Messages, Text Messages, or open More Settings to see these options. Then, tap Chat Features to turn on Send read receipts. Once it is turned on, the checkmarks in your previous conversations will change.