What a check cannot reach

Walk both strings position by position, find no disagreement across all 56 positions, and you have proved exactly one thing: the string in front of you is the same string as the one you compared it against.

That is genuinely worth having. It rules out damage, truncation, transcription error and substitution in one pass. It is the strongest thing anybody can do with a string on its own, and this board recommends it whenever a comparison is being done at all.

A comparison inherits everything from the thing you compared against. If your reference copy was wrong, a perfect match confirms you have faithfully reproduced a wrong address, and it will feel exactly like success.

This is not a hypothetical weakness, it is the main one. Almost every real problem with an address happens upstream of the reader, in where the address came from, and no amount of care at the reading stage touches it.

It is also why this site is careful about its own position. The board holds 3 strings supplied to it, prints them unchanged, and states on the addresses page that copying is the only operation it performed. It is a source, and being compared against does not make a source correct.

A string is a pointer. Checking a pointer confirms the pointer, not what it points at. Whether a service is running, whether it is the service you expected, whether it behaves as it did last week, whether it is worth using at all: none of that is a property of the characters.

People routinely collapse these two questions into one, because in ordinary web browsing the name and the thing feel like the same object. Here they are further apart than usual, because the name carries no meaning at all and nothing about it hints at what is behind it.

A check is a statement about the moment you made it. Strings do not change, but everything around them does, and a comparison performed once does not stay true about the world.

This board makes the same point structurally by refusing to carry any last checked marker anywhere. A timestamp on a check implies the check has a shelf life and that somebody is maintaining it. Neither is true here, so there is no timestamp.

• You can know a string is intact. Length, alphabet and final symbol between them catch damage.
• You can know a string matches a specific other string, if you do the full comparison.
• You can know which of the three published strings you are holding, since the three are far apart from each other.
• You cannot know your source was right, what is behind the address, or whether anything has changed since. No string check reaches any of those.

That list is short and it is the whole honest answer. The reading section on this board has spent eight panels on techniques for the second item, which is worth doing well precisely because it is the only item a reader can actually control.

If a check proves so little, why bother?

Because the thing it proves is the thing you can affect. The other questions need different tools and no amount of reading substitutes for them.

Does this site verify the addresses it prints?

No. It copies them and says so on every page. There is no probing, no comparison against outside sources and no verification step of any kind.