An order reference, read without the rulebook

Addresses and identifiers

An order reference is a short string that stands in for a record, and its rules are set privately by the site that issues it rather than by any public format.

The shape

This card begins with an admission, because the alternative is invention. This reference does not know the internal format of any order reference on Awazon Market. It has no length to give you, no alphabet, no prefix and no rule about where digits sit. Other cards state their rules because those rules are public. These are not, and filling the gap with a plausible looking specification would be worse than leaving it empty.

What can be stated is the set of properties that references have in general, because those follow from what a reference is for. A reference exists so that two parties can name the same record without describing it. That job forces a few things. It has to be short enough to retype and long enough not to collide. It has to survive being copied through a chat window, so it avoids spaces and characters that get reformatted. And it has to be identical everywhere the same record is mentioned, or it fails at the one thing it was made for.

Who sets the rules: the site that issues it, privately
What this page can state: the general properties below, and nothing beyond them
Constant width: references from one issuer are normally all the same length
One alphabet: digits only, or letters and digits, but not a mixture that varies between instances
Whitespace: none inside; a reference that contains a space is usually two things
Stability: the same string wherever the same record is named

xxxx-####        four letters, a hyphen, four digits
##########       ten digits, no separators
EXAMPLE-0123     a placeholder, not a format in use

Three arrangements that would each satisfy the general properties. None of them is claimed to be the arrangement any particular site uses.

Comparing two references you already hold

The private rules stop being a problem the moment you have two examples, because the format is then visible by subtraction. Put an older reference beside the new one and read what they share. If both are ten characters, ten is likely the width. If both begin with the same three letters, that is a fixed part rather than a coincidence. If the digits differ but sit in the same positions, you have found the variable part.

This is the only sound method available from outside, and it degrades honestly: one example teaches almost nothing, two give you the outline, several give you as much as anyone can have from outside. It also has a limit. A site can change its scheme whenever it likes, and a reference issued afterwards will not match a pattern extracted from older ones, so a mismatch is a question rather than a conclusion.

How to check it by eye

Testing a reference against itself

Read the reference straight through for anything that cannot survive being copied: a space, a line break, a quotation mark, a trailing full stop that belonged to the sentence rather than to the string.
Check that the alphabet is consistent. A run of digits with two letters buried in the middle is worth a second look, because references rarely mix in that way.
Compare it against another reference from the same source, if you have one, and note which characters are fixed and which move.
Look at where it appeared. A reference should read the same on the page that issued it and in any message that mentions it; if two copies differ by one character, the copies are the problem.
Ask how long it is meant to last. A string that changes every time you reload is not a reference to a record.

What a wrong shape means

Since the rules are private, wrong here has a weaker meaning than on the other cards. You cannot declare a reference invalid against a specification you do not have. What you can notice is internal inconsistency: a string that does not match the other references you hold from the same source, or one that contradicts itself by mixing alphabets in a way none of your other examples do.

The likeliest explanation for a reference that matches nothing is mundane. A selection one character short. A chat client that turned the string into a link and ate the punctuation at the end. A phone keyboard that capitalised the first letter. None of that is evidence about anything except how the string travelled, and the answer is to fetch it again from where it was issued.

Strings that are dressed as references

Some strings look like references and are not, and the giveaway is usually length or lifetime. A session identifier is typically much longer than anything a person would be asked to retype, and it often carries characters that would be awkward in a reference, such as underscores, hyphens in irregular positions, or a trailing run of equals signs. It also changes: get a new one, and the old one is meaningless. Those shapes belong to the session cookie card.

The other impostor is a piece of a link. Everything after a hash in a link is a fragment, and a fragment can be copied out and presented on its own, at which point it looks like a bare identifier with no context. If a string arrived from the tail of an address bar, it is a fragment of a link and should be read as one, using the mirror link card. A reference issued for a record and a fragment cut out of a link can look identical, and only where the string came from separates them.

What a correct shape does not prove

Assume the reference matches every other one you hold, character for character in the fixed positions. That result is thinner than it feels.

That the record exists. A reference is a label, and a label can be constructed by anybody who has seen the pattern, which is exactly what the comparison method above teaches.
That the record is yours. References are quoted in messages, and a quoted reference in front of you says only that somebody quoted it.
That the pattern you extracted is the real pattern. Two or three examples give you a plausible outline, not a specification, and the site never agreed to it.
That the format has not changed. Issuers renumber, add a prefix, or lengthen a field, and every reference issued before the change still matches the old shape.
That the reference means the same thing to the far end. Only the issuer can resolve it, and what it resolves to is not encoded in the characters.

What this card is not

No specification is published here and none should be read into the examples above, which illustrate the general properties rather than any live scheme. Strings that expire start at the session hub. A reference that is all digits and about ten characters long is worth checking against the epoch integer card before anything else. Identifiers that carry their own internal check, such as those on the transaction id card, are a different situation entirely, which is why the two sit in separate families.

Questions people send about this shape

Why will this site not state the length of an order reference?

Because it does not know it, and the format is set privately rather than published. Any figure given here would be a guess dressed as a fact, and a reader who compared a real reference against that guess would draw a conclusion from nothing. Comparing two references you already hold is the sound method, and it is described above.

Is a reference that is all digits worse than one with letters in it?

Neither shape is better. Digits alone are easier to read aloud and harder to mistype in some fonts; mixed alphabets pack more into fewer characters. What matters is that the issuer is consistent, since consistency is what lets you notice a string that came from somewhere else.

Can a reference be reused for a different record?

That is entirely up to the issuer, and the string carries no statement either way. Nothing in the characters marks a reference as unique, permanent or retired. If you need to know whether an old reference still names what it used to name, the string cannot answer, and neither can this site.

An order reference