xkcd is a webcomic by former NASA roboticist Randall Munroe. It is one of the most popular webcomics today, and is an influential part of geek culture. The focus is on math, science, Internet culture, and personal relationships from the perspective of an introverted geek — the same perspective shared by most of the target audience.
Although far from confrontational, xkcd has occasionally dealt with controversial topics, and is firmly and consistently pro-science. #154, for instance (see below), takes the attitude that although the scientific consensus on evolution and the age of the Earth is correct, there is no reason to be bothered by others' willful ignorance, so long as they are not in a position to make terrible laws based on that ignorance. One comic criticizes homeopathy, another comic attacks global warming denialism, several mock conspiracy theorists, and another is strongly critical of pickup artists. Aside from these topics, the comic is notoriously neutral when it comes to religion and politics, in contrast with its more abrasive sibling SMBC, though skeptics have proven an acceptable target at least once. Comics have criticized many logical fallacies, including appeal to moderation (690: Semicontrolled Demolition), the gambler's fallacy (1252: Increased Risk) and post hoc ergo propter hoc (925: Cell Phones).
 xkcd and the Internet
Munroe has a talent for putting relatively simple ideas in amusing and memorable joke strips; as such, xkcd is often quoted, linked to, and/or embedded in a post when there's a discussion on the Internet pertaining to science, math, personal relationships, or the Internet itself. Examples include the very common use of #285 (see below), using Wikipedia's tag, as a way of criticizing someone else's unsupported assertions; as well as...
 SIWOTI syndrome
SIWOTI syndrome is a strange psychological affliction affecting many Internet users - more likely an immune response than something viral.[citation NOT needed] The abbreviation comes from "Someone is wrong on the Internet", a phrase used in #386 ("Duty Calls"). The syndrome manifests in persistent attempts at convincing people who are (definitely and indisputably) wrong that they are wrong. It is suspected that, analogous to the role of toxoplasmosis in human aggression, the syndrome is the underlying reason for the existence of Internet flame wars, of the organized skeptical movement and of this very wiki.
Joking aside, while it wasn't in the original strip, the phrase "SIWOTI syndrome" is often used, including by skeptics. We'll leave to some other intrepid folklorist to determine which bright head(s) first came up with it.
 Argumentum ad xkcd
Some cartoons are gross oversimplifications, outdated, or a combination of both. This is okay as it's an internet cartoon which primarly aims to amuse, but some cartoons get repeated ad nauseam as if to make a point.
The "goto" cartoon is an excellent example of the latter. It's part of a general "goto is harmful" misconception, propagated by people who've never really programmed in languages with goto statements and just heard that it's harmful somewhere. You cannot have a discussion on goto anywhere on the internet and not have this cartoon posted by a nitwit. Knowing Munroe, the comic was probably intended to mock the misconception.
The "correct horse battery staple" password cartoon is both a severe oversimplification and outdated, but still gets quoted often. The problem here is that entropy is only part of what makes a strong password. Password crackers can crack these passwords with a technique known as a "combinator attack", where a cracker will read words from a dictionary and combine them. Passwords such as "howdoyouthink!", "momof3gr8kids", and "ilovemySister31" can be cracked by this in very little time  and security experts recommend against using it. You can still use the xkcd scheme, but you need to choose at least 6 words at random (the random bit is important and something many people get wrong).
Click to enlarge.
- xkcd, updates Monday, Wednesday and Friday
- xkcd What If? deals with various hypothetical science-related scenarios (such as "If you call a random phone number and say 'God bless you,' what are the chances that the person who answers just sneezed?"), usually updates on Tuesdays
- explain xkcd, a wiki explaining the jokes and references in each episode
- ↑ Here's an automatically generated list of examples.
- ↑ https://www.xkcd.com/292/
- ↑ Which it isn't, unless you abuse it; but this is true for any language feature
- ↑ https://xkcd.com/936/
- ↑ https://hashcat.net/wiki/doku.php?id=combinator_attack
- ↑ http://arstechnica.com/security/2013/05/how-crackers-make-minced-meat-out-of-your-passwords/
- ↑ https://www.schneier.com/blog/archives/2014/03/choosing_secure_1.html