WhatsApp now shows you when your message has been read
If you see a pair of blue check marks next to your sent message, you can take comfort in knowing that your words have been read by the intended target. If you sent a group chat, or a broadcast message, you won't see the blue check marks until every single recipient has read your missive.
Every message you sent will have a Message Info screen. To access it, open up a chat with a contact or group. Long press on the message you sent, and click on info or the info logo (small case "i" inside a round circle). Tap on it and you will open the door to a wealth of information. If you see the word Delivered next to your message, it means that your "media" was sent to the recipient, but was not yet seen by him/her. You will see the words Read or Seen when the recipient has read your message, or viewed your video or picture. For a voice message, it means that the message has been seen by the recipient, but not played. Played means that your voice message has indeed been heard.
If you're the sensitive type, don't take it personally if your message doesn't have the two blue check marks indicating that it has been delivered and read by the intended target. It merely means that the recipient of your message has not read it yet and will do so later. It could also mean that your target does not have the latest version of WhatsApp installed on his phone. Or, it could mean that either you or the recipient (or both) are having connectivity issues.
If you need to know if messages you send are being read, you might enjoy the new capabilities on WhatsApp, which is available for the iOS, Android, Windows Phone and BlackBerry 10 platforms. And yes, Happy Fifth Birthday to WhatsApp.
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source: WhatsApp via AndroidCentral