Facebook members can send and receive messages in real time using the Chat feature. For those times when chatting instantly isn't an option, members can make themselves unavailable by blocking. Chat settings vary, enabling members to remain completely or partially invisible. Facebook privacy settings enable members to block one another from chatting and, in extreme cases, from seeing a Facebook presence altogether. While there are some indicating factors, it is often difficult to determine for sure when you’ve been blocked from Facebook Chat.

Turning Off Chat Selectively

Facebook members can turn Chat off to temporarily block certain members, while leaving it on for others. This practice allows members to hide their presence selectively. You may or may not be able to tell if you’ve been blocked on Facebook Chat in this way. If a member doesn't show up on your Chat list with a green dot beside his name, she is unavailable to chat. If that member is presently engaging in other types of Facebook activity, you may see evidence in the form of News Feed stories, or ticker updates. This may be a sign that you’ve been blocked on Facebook Chat.

Turning Off Chat Completely

If a friend turns her Chat feature off completely, he is making himself unavailable to respond instantly to all chat messages. This practice is different from blocking, as messages you send are still received in his Facebook inbox. He can view your chat messages instantly, assuming he is currently using Facebook, or has opted to receive message notifications. When he turns on Chat, you will likely regain the ability to send and receive messages with him in real time. If the green dot is missing, but you see evidence of his Facebook activity, it may be a sign that he’s blocked you. It may also mean that he’s simply turned it off.

Logging Out

When a friend logs out of Facebook, she becomes unavailable to chat. This does not mean you’ve been blocked. It simply means she’s not receiving your messages, or anyone else’s, in real time. When she logs back into her Facebook account, she will become available to Chat unless she turns that feature off. Note that when a friend’s name appears in your Chat list with a mobile phone-shaped icon beside it, he is using one of the Facebook Mobile Apps on his mobile device.

Block Lists

When a friend adds you to her Block list, you lose virtually all connections with her. With the exception of any mutually tagged photos or groups to which you both belong, you become invisible to each other. Blocking covers all Facebook functions, including the Chat feature. It can be difficult to verify that you’ve been blocked, as there is no official notification. Your former friend may have deactivated or deleted his Facebook account without notice, or defriended you. A simple defriending is easier to validate, as that member’s profile is still visible to you with limited function. If after searching for someone, you can’t find anything, you’ve either been blocked, or that person has left Facebook altogether.