The verify approach that reads the string itself

Before I compare an address to any list, I can read the string itself. It tells me a small honest amount, and it is worth knowing what that is.

What the string is

An onion address is fifty six characters, all lowercase, drawn from the letters a through z and the digits two through seven. It ends in dot onion. The characters are the base thirty two encoding of a public key and some extra bytes.

That is a strong shape and it is easy to check by eye. Any string that is not fifty six characters, that has uppercase, that has one or the digits eight or nine or the digit one or the digit zero, or that does not end in dot onion, is not a v3 onion address.

The eye checks I can run without a second source

Count the characters before the dot. There should be fifty six. Counting is boring and effective.

Look for any uppercase letter. There should be none. A capital anywhere is a wrong string.

Look for any of the four forbidden digits. There should be none. A one, a zero, an eight or a nine somewhere in the middle of the string is a wrong string.

Read the last three characters. They should be lowercase letters or digits from the allowed set, and the string should end in dot onion, not in dot com or dot xyz or anything else.

What passing these checks does and does not mean

Passing the checks means the string has the shape of a v3 onion address. It does not mean the string is the address of nexus market. It does not mean the string is any market at all. It just means the string is a well formed candidate.

Failing any of the checks means the string is not a v3 onion address, and I do not need to run any other verification on it. Failing is definitive, in a way that passing is not.

The vanity prefix, and what to make of it

The three addresses on this site start with different vanity prefixes chosen by the market operator. The prefix is meaningful in the sense that it indicates the operator picked it on purpose. It is not proof of anything on its own, because vanity prefixes can be generated by anybody with enough time.

A string that starts with nexus is more likely to be a nexus market address than one that starts with anything else, but not certainly. A string that starts with something else is not likely to be a nexus market address. Neither of these is proof.

The prefix is a hint. It rides alongside the eye checks and does not replace them.

When to still do the compare

Always. Even after the string passes every eye check and starts with the expected vanity prefix, I still compare it against a list before I use it. The eye checks rule out obviously wrong strings. They do not rule out the many well formed wrong strings that also start with the right prefix.

The verify approach uses the eye checks to filter fast, and the compare against a list to verify. Both are cheap. Doing both is the honest workflow.

What this saves me from

It saves me from wasting time comparing obviously wrong strings against a list. If somebody hands me a string that has capitals in it, I do not need to check whether it appears on this site. It does not, because it cannot.

It saves me from typing a string into Tor Browser that could not possibly work. If the string is thirty characters long, it is not a v3 onion, and pasting it into the browser will fail without teaching me anything.

It gives me a small vocabulary for talking about addresses. When I can say the string has the right shape, I have said something specific rather than something vague.

Small habits to build around the string

• Count the characters. If it is not fifty six, do not go further.
• Look for uppercase. There should be none.
• Look for the forbidden digits. There should be none.
• Read the ending. It should be dot onion.

The tone of these checks

These checks are quiet and quick. They are the receipt for the fact that v3 onions have a legible shape. Learning the shape once is a small investment that pays every time I look at a onion.

The three addresses at the top of this article pass every eye check. So do many wrong strings. The eye checks are one small piece of the verify approach, and this article is here so I do not confuse them for the whole.

What this article is not. This is not a claim that reading the string is enough to trust it. It is a claim that some checks live in the string alone.