How to read a card here

Each card documents one string, block or file, and every card is laid out the same way, so the part you want is always in the same place.

A card is a reference entry rather than an article. You arrive holding something, or looking at something, and leave knowing whether it has the right shape. The six headings never change and never appear in a different order.

No card is a judgement about a particular string. The cards describe formats, and a format is a rule about which characters may appear and where they may sit.

The six sections, in order

The opening line

The sentence directly under the title says in plain words what the thing is. It exists so you can confirm you have landed on the right card before reading further. It is not a definition worth quoting elsewhere, and it says nothing about where your particular copy came from or whether it is still current.

The shape

This section states the constraint set: total length, the alphabet in use, which characters occupy fixed positions, which separators are required, and whether case carries meaning. It is a list of named constraints with at least one worked example under it. It is not a specification, and where a real format has options the reference does not cover, the section says so rather than pretending the rule is tighter than it is.

How to check it by eye

A short procedure, three to five steps, that a person can run by looking at a screen. Every card gives this block its own heading, because the procedures genuinely differ from one shape to the next. It is not a replacement for software that validates the format properly, and it is not built to catch a careful forgery. It catches accidents: truncation, a wrapped line, a paste that took half the string and left the rest behind.

What a wrong shape means

The honest reading of a failure. Most of the time a wrong shape means the string was damaged on the way to you by a mail client, a chat window, a screenshot or a hand retype. This section is not an accusation generator; it separates the small set of faults that can only come from an editing mistake from the larger set that could have come from anywhere.

What a correct shape does not prove

The section the reference exists for. It sets out, concretely and for that one shape, the questions that are still wide open once the format matches. It is not a warning label and it does not tell you what to do next. It marks where the check ends. The general form of the argument sits on what a shape proves, and where it stops.

What this card is not

One paragraph naming the ground the card deliberately leaves to another page, with a link to that page. It is there so cards do not creep into each other, and so you can move sideways in one click when you have opened the wrong entry.

Where the example strings come from

One rule governs every string printed on this site. Only three of them are real: the three Awazon addresses supplied by the site owner, which the template prints above this text on every page. Everything else has been manufactured, and manufactured in a way you can spot in about a second.

Where a format permits letters, examples spell the word example or run on a stretch of the letter x. Where the alphabet is hexadecimal or digits only, examples count up through 0123456789abcdef and repeat that pattern until the length comes out right. Armoured blocks show their first line and their last line with a bracketed marker where the body belongs, and never carry base64 content of any kind.

letters allowed
bc1qexampleexampleexampleexamplexxxxxxxxx

hex or digits only
0123456789abcdef0123456789abcdef

armoured body
[body: 24 lines of base64 characters, removed here]

A reference that prints plausible keys or plausible wallet addresses will eventually have one of them quoted back at somebody as though it were genuine. Fake by construction removes that possibility and costs nothing, because a counting-up string has exactly the same shape as any other string of the same length.

Reading a skeleton

Skeletons are shape diagrams. They use two stand-in characters and no others. A lower case x is one character drawn from that shape's own alphabet, whatever that alphabet happens to be. A hash mark is one digit, 0 to 9. Every other character in a skeleton is literal and has to appear exactly as printed: hyphens, full stops, colons, the word onion.

Repeat counts are always written out in words beside the diagram, since a long run of x is no easier to count than a long run of real characters. Where a run is too long for one line the skeleton breaks and says where.

xxxx-####       four alphabet characters, a hyphen, four digits
xxxxxxxx.onion  eight alphabet characters, then a literal .onion

A demonstration on an invented shape

The shape below does not exist anywhere. It was invented for this page so you can see the layout once without also having to learn a real format at the same time. Call it a shelf tag.

Total width

eight characters, always

Fixed part

three upper case letters

Separator

a single hyphen, always in position four

Variable part

four digits

Case

upper case only; a lower case letter is a fault

EXA-0123

exa-0123
EXA-012

The first fault is case. The second is width: seven characters where the tag needs eight, which is what a truncated paste looks like.

The eye check for a tag this short is a single glance. The hyphen sits fourth from the left, three characters stand before it and four after it. Real formats run long enough that a glance will not do, which is why cards hand that job to counting characters without a tool.

A wrong tag would mean the tag is wrong. It would not say who typed it, when they typed it, or why it came out short. That gap between the check and the conclusion is identical on every card, and it is the only thing the six sections are arranged around.

What sits around the card

The template supplies the breadcrumb trail, the links to neighbouring cards in the same family, the site index and the address panel at the head of every page. None of that is written into a card. For the whole set in one view, every shape on this reference lists them a row at a time. With a symptom rather than a format in mind, start at wrong shapes, filed by what you see. Character classes live on the four alphabets.