How do I know if someone has seen a message I sent in Facebook Messenger

You have sent a message to your friend and did not get reply and wondering if they read or even realized about your message?

In this post, you will get details about facebook messenger uses different icons for your messages sending, delivered and read or not.
The Facebook message can be sent via the website as well as through mobile app. If someone has not installed messenger on phone even they get a notice that they have a message unread. Later they can read the message on the website or they decide to install the app on phone.

Facebook messenger

Facebook messenger works very similar on website or app version. One can easily find if someone has read their message or not. They just need to know icons and it’s relation.

Below is web version of facebook messenger, it is very similar to mobile phone version just you do not see left and right box on app.
facebook read message

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How do I know if someone has seen a message I sent to Messenger?

Here just know what these facebook icons say about your messages. By knowing these signs you can know if your message has seen by your friends or not and also the time they read it.
Facebook messenger on web and mobile app version is very similar just the design differ. So, focus on what facebook messenger icon say.
message sending A blue circle means your message is sending
message has been sent A blue circle with a check means your message has been sent
message delivered A filled-in blue circle with a check means your message has been delivered
message read A small version of your friend or contact’s photo will pop up below the message when they’ve read it

Also know these icons

messenger not installed A small profile photo with gray letter f means they did not install messenger on the mobile phone.
messenger installed A small profile photo with messenge logo means they have messenger app on their mobile phone.