Help: Tags
Tags are basically keywords you can use to describe posts, allowing you to easily search and explore posts based on their content. Consult the cheat sheet for a full list of what you can search on.
Guidelines
When you're tagging a post, use the following guidelines:
Replace spaces with underscores
For example, maria-sama ga miteru becomes maria-sama_ga_miteru. This small concession makes other features much easier to implement.
Forbidden characters
The following characters are stripped from tags: commas and semicolons.
Name order
Characters with a first and last name are tagged with their first name first and their last name last. For example: tsubasa_oribe.
Use full names
Using full names reduces the chances of collisions. The definitive resource for character names is MyAnimeList or the Fire Emblem Wiki for Fire Emblem Characters.
Ask
If you're not sure whether a tag is right or wrong, then post a comment asking for some opinions. There are plenty of obsessive Danbooru fans who will gladly weigh in.
Types
Tags can be typed. Currently there are only three types: artist, character, and copyright.
Artist
Artist tags identify the tag as the artist. This doesn't mean the artist of the original copyrighted artwork (for example, you wouldn't use the barasui tag on a picture of Miu drawn by hanaharu_naruko).
When tagging something, you can tell Danbooru that a tag is an artist tag by prefixing it with artist:. For example, tagging something artist:mark tree will tag a post with mark and tree. If the mark tag doesn't already exist, it'll be created with the tag type set to artist.
Character
Character tags identify the tag as a character. They work exactly like artist tags, only you prefix with "character" (or "char").
Copyright
The copyright type indicates the tag represents an anime, a game, a novel, or some sort of copyrighted setting. Otherwise they work identically to character and artist tags, only you prefix with "copyright" instead (or "copy").
Ambiguous
Tag ambiguity is handled much in the same way that Wikipedia handles ambiguity. Users who search for an ambiguous tag are directed to a disambiguation page on the wiki, where they can clarify what they want to search for.
The flag for marking a tag as ambiguous is separate from the type. This means that an artist tag could be marked as ambiguous, for example. To mark a tag as ambiguous, prefix it with "ambiguous".