Document channel name and thread name restrictions

[MarcusOtter]

Description

Posting to POST /guilds/{guild.id}/channels or POST /channels/{channel.id}/threads or POST /channels/{channel.id}/messages/{message.id}/threads is allowed with any name. However, Discord removes characters that it considers invalid and sometimes replaces it with something else or removed entirely. It would be very beneficial for us developers if this replacement process was documented, preferably with a RegEx of characters that will be transformed, and whether they will be replaced or removed.

Suggestion

I believe the Application Command name is documented excellently, and I would love something like this for thread names and channel names:

CHAT_INPUT command names and command option names must match the following regex ^[-_\p{L}\p{N}\p{sc=Deva}\p{sc=Thai}]{1,32}$ with the unicode flag set. If there is a lowercase variant of any letters used, you must use those. Characters with no lowercase variants and/or uncased letters are still allowed. USER and MESSAGE commands may be mixed case and can include spaces.

Usernames and nicknames also has decent documentation on what is allowed in a Discord user name, which one could quite easily create a RegEx for (but it would be even better if it was supplied in the documentation).

Use case

There are many reasons a developer would want to know this. In my case, I let users pick a default name for threads created in a certain channel, which I do from a modal with a text input. Today, if they enter any combination of only invalid characters, I have no way of knowing in advance whether Discord will accept this name or not, because I don't know what the invalid characters are. There is a risk that all of them are invalid. All I can do is blindly accept it and hope it doesn't throw an error once my bot eventually creates the thread (which it would if the input was something like ////#####::: because the remaining length would be 0 after Discord removes all characters). It's either that or trying to manually find all invalid characters by reverse engineering it before continuing with this feature, which is really frustrating.

If you want to help reverse engineering it, reply to this post.

[MarcusOtter]

Reverse engineered findings

Feel free to post replies on this post with your findings and I'll include them. Helps other people implement this until Discord releases their official restrictions.

Channel names

• Spaces are replaced with -. Tested with U+0020, U+00A0, U+1680, U+180E, U+2000-U+2009, U+200A, U+200B, U+202F, U+205F, U+3000, U+FEFF.
• Characters that have a lowercase variant are transformed into it (may only be client side, see below).
• ???

Thread names

• The following characters are removed: /\"#:<>@
• ???

[fatboychummy]

Characters that have one are transformed into their lowercase variant.

Have one what? Uppercase character? If so, it seems that's display-side only, or at least was that way up until recently. One of our moderators trolled and set a channel name to ThIs KiNd Of CaSe, because people using third-party discord clients saw the uppercase characters, while everyone else just saw the normal lowercase.

Do note this was multiple months ago now, it may have changed.

[MarcusOtter]

Have one what?

Characters that have a lowercase variant

it seems that's display-side only

Very interesting, I don't have time to test right now but if someone could verify that would be great! Thanks for the input.