On tex.stackexchange, I had to break a chat message into pieces because it was too long. Comment fields on the list itself say how many characters are left, but chat messages don't, and I can't find information on their size. (I probably just don't know where to look.)

Chat messages do seem to be smaller than comments, and a friendly co-member of meta.tex.stackexchange confirmed this by actually counting what he typed in (about 600 for comments vs. 500 for a chat message). Since the reason for my being in the chat room was in answer to a request to divert "extended comments" to a chat, I find that request rather impertinent.

A clear indication of the permissible size of a message, or a count-down a la comment, or even both, would be very welcome. It would also be welcome to have a message size that is at least no smaller than that of a comment in the main list.

  • 4
    It is 500 (I don't think it's documented anywhere, though), but I don't know the reason for the use of a "Whoops, too long!" message versus the countdown. Perhaps to save screen real estate without being annoying.
    – Tim Stone
    Jan 20, 2012 at 23:23
  • @Tim this is indeed 500, maybe time to post this as answer? :) Oct 5, 2015 at 17:59

2 Answers 2


The limit of a normal single line message in chat is 500 characters.

single line limit

If you enter an explicit line-break (shift+enter on a Windows machine) you can lift this limit of 500 characters.

more then 500 characters

but in the transcript you'll still see only 500 characters. Users would have to click the See full text link to see the complete message:

larger then 500 messages

I didn't test the actual maximum allowed size of a multi-line chat message but I wouldn't be surprised if it is 30,000 characters, similar to what it is for posts. If you are lucky (which it turns out we are) it is nvarchar(max) in the database, allowing for 1 billion characters ... In which case you could technically backup your harddrive in a chatroom ...

It is true that comments on posts can be longer, they are capped at 600 characters. However, when comments are moved to a chatroom, they are not hindered by the 500 characters single line restriction. Here is an example of an 557 characters imported message

  • i'll accept the answer, and appreciate the extra information on how to go to a second line. but i'll have to check again on whether the limit on comments diverted to a chat for tex.stackexchange are (still?) capped at 500 characters -- i wouldn't have asked about this if i hadn't been interrupted at a length less than allowed in a comment on the main site. (i agree that comments imported to a chat aren't truncated. i was asking about new comments.) Jul 2, 2017 at 17:40
  • Yeah, the 500 chars limit is the same for normal rooms or for rooms that are created due to an comment import.
    – rene
    Jul 2, 2017 at 17:57

Thanks to @lyxal’s efforts, we found out that the practical limit for multiline messages (where it actually gets sent with no time out) is about 4 million.

  • 2
    If the error is timeout it means you are just testing your upload speed. It's impressive, but not relevant for what's being asked. Aug 4, 2023 at 14:58

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