Messanger has an inbuilt feature which confirms the delivery of the message with the status of the message whether it is read by the receiver or not in Facebook Chat.
If you don’t want to let your friend know that you have read the message for the privacy issue. There is no default setting in Facebook Chat to disable this feature. So if you want to turn off “Seen By”, you can do it by using a simple Chrome extension on desktop or laptop.
Hide Seen By in Android Device read here the complete guide
Check the Facebook Chat Messages Without Open it
1. Open your favorite browser, for explanation here I am using Chrome.
2. Now get Chat Undetected Software for windows and install it. This will detect the browser you are using and according to your browser, it will automatically download the add-ons for Firefox and extension for Chrome.
3. Now go to download folder and install the downloaded add-on or extension for your browser.
That’s and now you are free, no one will know whether you have seen the Facebook Chat message or not.
If you don’t want this disable the feature for Seen By, You can remove it by uninstalling or disabling the Chat undetected for that you just need to open Setting → Extensions → Disable or uninstall Chat Undetected.
Give it a try if you have any query regarding this tool you can ask in the comments section and don’t forget to share this with your friends and show your smartness.