Do read-receipts for Facebook messages work only if recipients are using a mobile app? Or even if recipient views on web interface of Facebook? From my experience I guess when recipient views private message on web, then no read-receipts are generated for sender.
Request to Editors : To be careful not to negate criteriae of the question while editing
No, even when the user's using a computer the receipts will work, however, some developers made out some unofficial extensions that prevent your browser from sending that receipt, and yes, your friends may be using one.
Nice answer
Thanks!
How come read-receipts ( Seen by ) were not generated in few of my messages even after the recipient had replied to the message
To understand that you have to understand to the read-receipts work:
Facebook has implemented a script in the Web chat box that is programmed to send a database entry once the box is highlighted by the keyboard or the mouse, but, the extensions that some developers made have a purpose to automatically and instantly remove the script Facebook made for this purpose, so as result, the Facebook system does not know when your contact "reads" the message although in fact he really did.
Thanks
Superb answer
Very talented and knowledgeable answer
Use your talent and knowledge in such ways ( for reasons ) and at places that our Creator is satisfied and not attempting to satisfy own self
Thank you for appreciating my humble answer.