Here is the short answer. On English Wikipedia, the address en.wikipedia.org/wiki/Joker is a disambiguation page, a list of everything that shares the name. The article about Batman's archenemy sits at /wiki/Joker_(character). If you came for the comic villain, the second path is the one you want. If you came for the 2019 movie, that is a separate article again.
Why the plain title is not the character
Wikipedia gives a bare word like "Joker" to the disambiguation list once several notable topics claim it. That is a naming convention, not a mistake. The list links out to the character, the film, the soundtrack, the playing card, and a handful of comic series. It is worth a skim if you are not sure which one you need, since it is short and grouped by topic.
The paths you probably want
- en.wikipedia.org/wiki/Joker_(character): the DC Comics character, publication history, and alternate versions.
- en.wikipedia.org/wiki/Joker_(2019_film): the Todd Phillips film with Joaquin Phoenix.
- en.wikipedia.org/wiki/Joker_(soundtrack): the score and album for that film.
- en.wikipedia.org/wiki/Joker_(playing_card): the card, for rules and game references.
Titles that need a qualifier get one in parentheses. That keeps two different "Joker" articles from fighting over the same address.
How the address is built
Every article sits under /wiki/ followed by its title. Spaces turn into underscores, so "Joker (character)" becomes Joker_(character). Parentheses stay as they are. If you paste a title with normal spaces into the address bar, the browser usually sorts it out. The underscore version is the one you will see in the bar after the page loads.
The mobile site uses the same path with an m in front of the domain, and other language editions keep their own titles, so the German or Japanese page may not match the English one word for word.
Checking you landed on the right page
Look at the first line of the article body. A disambiguation page says so outright and shows a list. A real article opens with a definition sentence. If you see a short italic note under the title pointing to another topic, you are on a related page and the note tells you where to go next.
Redirects do a lot of work here. Typing "The Joker" or a variant spelling often drops you straight onto the character article instead of the list. That is normal and it is why two people can compare addresses and both be right.
If you need a stable reference for citing, open the page and use the permanent link in the sidebar. It freezes the exact revision you read, so a later edit cannot change what your citation points to.
Quick checklist
- Decide whether you want the character, the film, the soundtrack, or the card.
- Use the parenthetical path for anything other than the bare name.
- Confirm the first sentence matches the topic before you copy the address.
- Grab the permanent link if the page is going into a citation.