Android - Whatsapp - last time seen online - what does it mean?
A single green tick mark indicates the Whatsapp servers have got your message. A double green tick mark indicates that the recipient's device has got your message.
However, it doesn't automatically mean that the user has read or seen the message.
The last seen online may merely indicate that the user may have been talking to someone on the contact list or been in the Whatsapp application for any reason like adjusting settings etc.
No guarantee that the user has read your message.
Taken from http://www.whatsapp.com/faq/en/general/20951546
My doubt is whether "last seen" indicates that the user has actively opened the applicaction, or that the application has been running on background connecting to WhatsApp servers? The WhatsApp FAQ now says:
"Last seen at..." refers to the time the contact left WhatsApp
But googling I found an old WhatsApp FAQ answer for the same question, maybe referred to the old versions:
"Last seen" simply indicates the state of the device network connection and not if the application is actively in use. For example, on some operating system such as BlackBerry and Android, the phone will connect on it's own if it has a new incoming message even if the phone is not in active use at the moment
I have seen "improvements to "last seen" and "typing..." correctness / timeliness" in the 2.7.4705 version (2012-MAR-05) changelog
I will test it
WhatsApp uses push notifications (the server notifies the device) so seems not neccessary connecting periodically to the server looking for new messages (pull). Another question is if once a notification is received the app connects to the server for new messages downloading. In any case, the question is if WhatsApp takes into account the connections with the app in background for the "last seen" indicator.
Just to bring this current, WhatsApp have updated their What are those check marks next to my messages? page to highlight that there's a new feature to see when a message is actually read.
Check marks will appear next to each message you send. Here is what each one indicates:
message successfully sent.
message successfully delivered to the recipient's phone.
the recipient has read your message.
It's still likely that a message will show as delivered before a user has been "online" to actually read it.