The new messenger web app launched by Facebook is a standalone app. You can access it via messenger.com. The facebook users can continue chatting via facebook as before, but the messenger app is aimed at being a completely messaging service without the annoyance of news feed and the profiles.
To use messenger, there is no need for special registration. You just need to login with your facebook credentials. It works on the similar lines as the mobile app. It does have support for voice calling, stickers and emoticons.
Facebook has been attempting to make the messenger service a Platform rather than just a messaging service. They are working on to make it compatible with online retailers so that users can interact with the them and get updates on the status of orders. If you have the payments feature enabled on your mobile app, it will get included in the messenger.com. Contents from third party apps already created on the mobile app can be integrated into the web app, but you cannot create it from the web app.
However, it must be said that the app is still in its infancy. If you want to block a user or change privacy settings, you need to visit the main facebook website. Settings are not comprehensive. Cat heads and the groups are absent. But, given the track record of Facebook, we can expect the developments soon.
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