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Possible Duplicate:
How do comment replies work?

In Twitter the at (@) symbol makes the tweet appear in the user page.

Does it do anything on Stack Overflow?

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marked as duplicate by random Jul 10 '10 at 17:14

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up vote 10 down vote accepted

It does not do anything as far as programming. It is just a social construct we have all adopted to show who we are addressing our comment at.

And now, it also notifies the target:

Normally, you only get notified of comments when you own the post.

You will now get notified of any comments that refer to you by @username in a comment, even if you do not own the post.


  1. Only applies to other people in the comments that you are commenting on.

  2. Response must include @username that you are referring to, where "username" is a reasonable match to the user's current display name (as seen in the comments above yours).

  3. There must be a starts-with, case insensitive match of at least THREE characters to the displayname. So @a and @ab will never match anyone or anything.

  4. Spaces cannot be used to match, so if the person's display name is "Peter Smith" then just use @peter to match.

  5. Matching is performed in reverse chronological order, so if there are five people named "John" in the comments, writing "hey @john, have you considered apples?" will match the most recent John to comment.

  6. Only one person can be replied to at a time in a comment. The first one "in" wins.

share|improve this answer… discusses this. "the "notify when people say my name" is really interesting, but requires unique names which we don't enforce" – dbr Oct 4 '09 at 18:05
it's just the twitter construct, the original meaning of @ is the at sign, it has been traditionaly used to denote host in URIs. i don't see a reason to use @ in this context in different places. i also wonder if it really triggers something, when used in stackoverflow comments – mykhal Jul 5 '10 at 17:30

I would back the idea of having the @[USERNAME] actually try to predict the user being addressed and place a link to their profile. Overall though, @TheTXI is correct, it is becoming a social construct (thanks to twitter) that we are beginning to adopt and adapt into other tools.

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I still haven't quite fallen into it. I notice that I am still one of the few people who addresses people using the "[UserName]:" prefix instead of "@[UserName]" – TheTXI Jul 16 '09 at 2:09
you shall give in.... the construct will overwhelm you :) – RSolberg Jul 16 '09 at 2:25

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