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  • How do I respond to a specific user when entering my comment?
  • Will they be notified?
  • What do people mean when they talk about "pinging" another user?

Related: How do I view my recent replies?

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I had a really hard time finding this question because I was trying to search for "pinging a user", which is not a term used anywhere on this page. Hopefully, this comment will help the next person who does that. –  Ilmari Karonen Nov 13 '12 at 16:29
@IlmariKaronen: Since comments are not indexed, I think an edit to the question was in order. (Thanks for the suggestion.) –  Jon Ericson Mar 21 '13 at 12:53
I strongly suggest we need a common term for this, how about namechecking? Otherwise it's insanely search-hard, as @IlmariKaronen mentions. 'notification' is too bland, and connotes routine notification of non-comment things. Mods if you agree, please create a tag namechecking and apply to this? –  smci Apr 12 at 23:35
Recently, on numerous occasions, I've tried to start a comment with at-symbol and the name of a previous commenter, and after posting the comment the at-symbol-and-name has disappeared completely. Other times it seems to work fine. Any explanation for this behavior? –  gwideman Apr 15 at 1:18
@gwideman, see point 10 in the accepted answer. –  Arjan Apr 17 at 19:56
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1 Answer

up vote 264 down vote accepted

You can use @name syntax anywhere in your comment to reply to a specific user. This will notify that user in their global inbox. There can also be notification through email if you click the "email settings" link at the lower left of your global inbox.

In short:

Some more detail:

  • The first author of the question or answer will always be notified of any new comment.
  • You can explicitly notify one (1) other user if they have a current (non-deleted) comment on the post or their name appears anywhere in the revision history (only those who have commented will show up in the auto-complete dialog though).
  • Use @name, where name is the username with all spaces removed.
  • Single trailing punctuation such as a dot, comma, or colon is ignored, e.g. @name, yes
  • Multiple trailing dots work as well, e.g. @name... yes
  • Things like @op, @downvoter or @all have no special meaning.
  • If a user comments on their own post and there is only one person who has previously commented, then that person is also notified if @name is forgotten.
  • Tab name completion can be used, and that knows when @name is unnecessary and will then not automatically complete names. It also does not work for editors.

And all details that make this work:

  1. The question and answers are all considered independently. For example, if Alice was the author of, commented on, or edited the question or her answer, then you cannot notify her by commenting on Bob's answer (unless Alice also participated in that answer), and vice versa.

  2. You must include @name, where name is a reasonable match to a user's current display name. Users who have not set a display name in their profile are not notified.

  3. If the first word in the display name is at least three characters long, then there must be a starts-with, case-insensitive match of at least three characters in the display name. This means @a and @ab will never match anyone, unless a user uses a first word that is only two characters. Like: @Jo will notify Jo Miller, but not John, and @B. will notify B. Gates, but not B.Gates. If there are more than three characters in @name, then all given characters must match (neither @alix nor @aliceinwonderland will match user Alice).

  4. Matching is performed in reverse chronological order, so if five people named John are participating, @john will match the most recent John. (Use the next rule to differentiate.)

  5. Spaces are removed from the display names for matching purposes. So to match Peter Smith you may use @pet, @peter, @peters, or @petersmith. The last two are useful if Peter Jones is also participating, who can then be distinguished using @peterj. However, no spaces are allowed in the @name itself. Like to notify P Smith, one must use @psm or @psmith. (Here @P Smith would be handled as just @P, which is too short.) Single quotes, dots, dashes and underscores should not be removed.

  6. Special characters are replaced with their simple equivalent. To reply to Piëre you can use both @piëre and @piere. And to reply to Jörg you could use @jorg, but not @joerg.

  7. Comments containing more than one @name are blocked unless they contain a backtick `. In the latter case, only the first name mentioned using the @name syntax will be notified. For example, @alice @bob Hi!` will notify Alice (if she has participated in that post), but not Bob.

  8. An exception is the case when the first @name either matched nobody, or matched the post's author (and thus isn't necessary); in this case, the next @name will be checked.

  9. When editing a comment within its limited editing period, if you change or add @name, the notification may or may not reach the new recipient depending on timing.

  10. The first author of the question or answer will always be notified of any new comment. There is no need to use @name to notify them. (You may still use it for clarity, if needed; however if only you and the author have been commenting on the post so far, the @name will be automatically removed from the beginning of the comment, as it adds no value.)

  11. The notification must begin with a space or be at the start of the comment. For example, you cannot use markup such as italics.

  12. Single trailing punctuation such as a dot, comma or colon is ignored. Like @name, yes works, but @name... no does not. (Though a dot is valid in a username, the last dot is removed for matching, so @St will notify St. although only two characters are used.) Hyphen can also be part of users display name, hence not ignored so @name- ... will not work.

  13. The notification only works for the username that is current at the time the comment is submitted, not any previous username(s) the target may have had.

The exact matching rules are not documented, but extensive tests performed on 30 August 2011 indicate that the following algorithm is used:

  • Take the first word immediately following the @, where the word boundary is determined by a space, a character not valid in user names (such as : , / ! ?) or the end of the comment.
  • Remove one trailing dot . from the resulting string if applicable (and if the string has more than two characters).
  • If the remaining string ends in ' or 's, remove that piece from the string.
  • The resulting string will be matched against the user name with spaces removed.

Example: The comment ends with @O'Conner's.). The word immediately following the @ is O'Conner's. since ' and . are valid in user names. Then the trailing dot is removed, and finally the 's is removed, resulting in O'Conner.

Some examples of supported notifications:

  • @name some text
  • @name: some text
  • @name. Some text
  • @name, some text
  • some text, @name
  • some text, @name, more text
  • Some text, @name.
  • This is mentioned in @name's comment.
  • @P. for both P. Smith and P. Jones (whoever commented most recently), but not P.Smith nor P.Jones. Likewise, @P. Smith is handled as @P., so also matches P. Smith or P. Jones.
  • @psm or @psmith for P Smith
  • @peters or @peterj for Peter Smith or Peter Jones respectively
  • @name... now works.

Examples that will not trigger notifications:

  • abc@name
  • *@name*
  • *@name:*
  • [@name](http://some-url)
  • @[name](http://some-url)
  • @P Smith
share|improve this answer
Can you @ notify someone even if they haven't posted anywhere on the question? –  Phillip Schmidt Jun 13 '12 at 21:44
@PhillipSchmidt No, only users who participated in the post. –  balpha Jun 15 '12 at 8:13
@balpha. Wouldn't it be nice to comment someone by it's userid? I needed to do it many times, most recently I quoted Jon Skeet's book, and wanted his approval to the quote. I had to comment him on other answer of him with an off-topic comment because of this feature lack. What do you think? –  user173320 Jun 28 '12 at 13:40
@gdoron So everybody and their dog puts an @22656 comment on their C# question to get him to answer it? Unconditional messaging (as in, not restricted to participants in the comment thread) has been declined many times, and that's good. –  balpha Jun 28 '12 at 13:55
D'you know, it might be a good idea to turn the @name text into a number (the user id (at the server end)). When the text is rendered, it shows as the current name. This way, if the user changes his name, the reference is still valid. –  bobobobo Sep 3 '12 at 15:12
I was really looking for how to add a comment, like this comment here, because in the other post it doesnt have the "Add Comment" button, and in the other post i want to add a comment to a dumb answer that doesnt even answer the question and it has the most votes –  MrCambron Sep 11 '12 at 9:39
@MrCambron, on non-meta sites, you need 50 reputation to leave comments on other people's posts. –  Marti Jan 9 '13 at 17:18
In your link in “In short”, there is nothing about comment replies. Actually I come from the help and in the help there is nothing explaining comment replies. It would be nice to fix that. –  Nicolas Barbulesco Nov 3 '13 at 18:47
This will notify that user in their global inbox global inbox. This feature (and the blog post it links to) is a little outdated now –  Cruncher Dec 20 '13 at 15:27
To "a ♦ moderator" or to "an ♦ moderator", that is the question. –  bjb568 Jan 4 at 8:45
Proposals for edit: "1. Notifications apply to the author, users with active bounties ..." - A) please specify author of what to be absolutely clear - possibly author of the commented post? B) there can be more than one active bounty? So possibly change to "user with active bounty"? I don't want to change it myself because I am not sure I understand the topic enough. –  Tomas Jan 17 at 10:37
I think it would be helpful if the "@" text was linkerized or otherwise specially formatted, for feedback - otherwise it looks like it didn't work. (And in fact, without running the algoritm above in your head, you really don't know whether it worked or not). –  ytpete Mar 27 at 20:51
But new user may not be aware of @name method, and if they just commented for some one how could they know? –  Haris Mar 29 at 8:09
The @all goes to a deleted page, which was deleted by its author, is it possible to undelete that page, or update this answer to remove the link? –  Cupcake Apr 25 at 20:41
@balpha: If someone has a bounty on the question, but they have not participated in an answer, can they be notified in a comment to that answer as well? (My guess is no, but it seems possibly ambiguous.) –  robjohn May 7 at 19:01
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protected by Shadow Wizard Oct 12 '12 at 9:14

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