Explain Xkcd

Truly Universal Outlet

|< < Prev #3186 (December 26, 2025)

Title text: Building Inspectors HATE This One Weird Trick

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Explanation

This comic shows a layout for a universal outlet which would theoretically fit any mains power-plug. Throughout the world, countries and regions have their own standards for outlets, including their shape, contact amount, and voltage. When traveling, or otherwise using devices from other countries, it is often necessary to have an adapter to connect one type of plug to a different outlet.

The comic shows an outlet with fifteen sets of holes merged together, so that any of those plug types might fit. In reality, it's possible that a plug may not be held securely, and it may fall out or lose contact. For example, the hole for types D, M, and O at the top of the outlet has three distinct holes, some of which are entirely contained within others; a prong for a smaller type would not make contact with the walls (without particularly spring-loaded contacts). Different outlets can also mean different voltages, which can risk damage if devices do not account for it. Although universal plug adapters actually exist, none of them are as 'universal' as the one shown in this comic, most likely due to aforementioned safety concerns.

Also the comic seems to misrepresent type E sockets - it seems like Randall wasn't aware of (or ignored) the fact that type E sockets has a grounding pin that protrudes out from the socket, and rather represents it as if it were a hole in the socket instead. In reality it would be difficult to make a socket that safely grounds type E plugs without being simultaneously incompatible with a large number of other plugs that aren't designed to accommodate the grounding pin, probably requiring the prominent socket-pin to be a spring that retracts far into the socket when pressed by a plug's ground pin.

The comic also seems to not notice the lack of grounding for full compatibility with F plugs. This leaves them in the same state as type E above. This could be fixed by adding the extra pins for grounding. Given that most plugs in E and F regions are compatible with both standards (CEE 7/7) and have the E ground connected to the F ground through a front plate bigger than the hole for the E standard, it would be theoretically possible to make a mostly universal plug, with the exception of pure CEE 7/5 Schuko and some pure French-style CEE 7/6 that don't have the external metallic plate, but both of those are vanishingly rare, phased out by the CEE 7/7.

The title text references the classical clickbait format "<organization/role> hate this one weird trick," implying <organization/role>'s services will be no longer needed if the trick works out as it claims to, and therefore (according to the clickbait) they do not want you to find out about the trick. In this case, however, building inspectors likely hate the design solely because of its grotesque safety problems.

While this comic is not part of the Cursed Connectors series, it does follow a similar theme of unorthodox or dangerous ways to make electrical connections.

Transcript

[A diagram of an electrical outlet is shown, merging the holes of many international outlets. Dashed lines indicate individual standards' holes, which are labeled by their corresponding letter from A to N. The entire outlet is the combined area of these holes.] Wiring tip: To make your building friendly to international visitors, cut holes in your outlet plates to make them compatible with all fifteen IEC plug types.

Trivia

• This comic was released on Boxing Day during Christmas of 2025, but makes no reference to Christmas.
  • The previous comic, released on Christmas Eve, 3185: Sauropods also made no reference to Christmas.
  • This thus marks the second year on a row without any Christmas comics released during those days, see this trivia from the comic 3029: Sun Avoidance released on Christmas Day in 2024 (first time such a day was not given a Christmas comic).

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