Google+ circles have been rolled into chat across all Google sites, including Gmail, iGoogle, Orkut, the Google Talk client, and even third-party apps. Previously, Google Chat was based on email addresses and was a part of Gmail. When Google+ launched, it had the same email-based chat widget that Gmail has. Now, anyone in your circles who has circled you back will appear in chat.
The chat list still shows your most recent contacts, rather than your full list, and you can use the search box to find people who don't appear. According to Google+ support documents, the chat relationships you had before this update are preserved and take priority. For example, your existing block list still applies. The order of contacts might appear differently in different places, but this Google+-enabled chat now applies across the board.
Orkut, Google's other social network, Google+ connections are now the way chat works. It's a small but significant step toward Google+ being the social layer underlying all Google sites.Now that circles are the main organizing principle of Google Chat, Google+ takes on a primary social role across important Google properties. Even in
Learn more in Google+ help.
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