I would say that rarity should be lowered.

Any suggestions? 🙂

Something around 0.3

Why 0.3? I'd say higher like 0.5 or 0.6 because:

1. The string has to start with 1Z
2. It needs 7 chars 0-9A-Z
3. It has exactly 2 numbers
4. It has 8 numbers

Also, can we make it:

- ^(1Z[0-9A-Z]{6}[0-9]{2}[0-9]{8})$
- + ^(1Z[0-9A-Z]{6}[0-9]{10})$

?

I think 0.4 or 0.5. And yes, regex should be changed.

The idea of the 2+8 split is because the first 2 digits in this group represent a service indicator code and perhaps it could be captured and handled in the future.

Aside: I wonder if the "rarity" could be estimated more reliably through some entropy-based measure 🤔

service indicator code

We have precedence for this called sub-categories. See the Mastercard / Phone Numbers regex. I am not sure it'll work on data in the middle of the regex, we may need to change the code for that :)

Aside: I wonder if the "rarity" could be estimated more reliably through some entropy-based measure 🤔

Probably! Currently I am estimating it based on what I see when people post this:

And also whether we have any false positives.

@P403n1x87 You can use subcategories with regex method for that.