Tumblr launched instant messaging for Android, iOS and the web. Users will be able to send and receive messages, not much different from Facebook Messenger.
This is a smart move, and in fact applies to every site that lets users send each other messages. When you talk of chat apps, people tend to think of a few big players : WhatsApp, Facebook Messenger, iMessage and Hangouts (disclosure: I work for Google). But who’s to say that chat should be offered only by a few large players with hundreds of millions of users each? Any site that lets users send messages to each other is in effect a chat system . And there’s a huge long tail of such sites. Stack Exchange, for example, has four million registered users. Let a thousand flowers bloom.
On mobile, thanks to notifications, people can receive messages even from sites they don’t otherwise check regularly. Mobile lowers the barrier to participating in a chat on a small site.
Not only that, contacts are available for all apps to use, unlike on the web  where your contact list on a service is seized by the service to fulfill their objectives, not yours. Thanks to contacts being available to all apps, an app like Tumblr or Stack Exchange can connect you with people on their site who are in your contact list, growing your network. It’s one thing if the people you know don’t use a site you do, like Stack Exchange. But it would be sad if they did use the site, and you couldn’t discover them. Mobile fixes that problem.
One problem, though, is the lack of real names:
Do you want to hear from jiffycube or tubastank? I certainly don’t, and this is the childish, crude aspect of Tumblr, full of lame GIFs that may appeal to 13-year-olds. Still, if you do read their blogs on Tumblr, I suppose you would identify the name and it wouldn’t be a problem.
At a high level, let different apps experiment with different takes on real names. A site like Facebook insists that everyone use their real name. Other sites support or even encourage pseudonymity. When there’s a profusion of chat apps, different parties can try different approaches and stick with what works for them. And users can use whatever model they prefer. Everyone wins.
Tumblr’s chat app is a refreshing development. Rather than an anointed few large players running chat, let a thousand flowers bloom.
 Chat apps fall into a few categories: dedicated chat apps (WhatsApp, Viber, Telegram, and so on), apps that come with the OS (Hangouts and iMessage), and social networks (Facebook).
 One downside of the “everyone is a chat app” outcome is that I don’t want more interruptions. It’s high time developers learn to respect users’ time and attention, and not interrupt them with notifications. They should use “silent” notifications that don’t make an audible noise, don’t vibrate the phone, and don’t turn on the LED if there’s one. Just put up a notification silently in the system tray, for users to discover when they next unlock their phone. Or gate the notifications to say, no more than one a month. There are many ways to combat notification overload.
 This is ironic, because we generally think of the web as being more open than native apps.