Contacts' online status can be seen on their
profile photo.
A green sign in profile picture indicates
online while no sign appears while someone is
offline. The online status is viewable to contacts
only.
When contacts are offline, you can also click into
the chat box to check when messages were last
seen by contacts. If you don't have this feature,
please update imo on Apple App Store or
Google Play Store.
Note:
Contacts can set who has access to his last
login time, including all contacts / friends
/ nobody. If you can't see friends' last seen time,
it may be caused by old imo version, network
delay, or contacts set messages to been seen
by nobody.