Generate random PIN codes of configurable length with options to avoid sequential or repeated digits.
Enter a length and the tool returns a numeric code in which every digit is chosen independently and uniformly from 0-9, so no digit position can be predicted from the others. Two optional filters remove the patterns people actually pick: 'avoid sequential digits' bans runs such as 1234 or 567, and 'avoid repeated digits' bans codes such as 1123 or 2222. The surprise most users hit: randomness produces 0000 just as readily as 4829, and a 4-digit code - random or not - has only 10,000 possibilities, so generation protects against human guessing patterns, not against systems with unlimited attempts.
A concrete input and expected output from the current implementation.
Input
Length: 4 | Avoid repeated digits: on | Avoid sequential digits: on
Expected output
7149 (one possible result; any code that passes both filters is equally likely)
Digits are chosen uniformly from 0-9 and codes that violate an enabled filter are excluded, so all surviving codes stay equally likely. 7149 clears both filters - its four digits are all different and no adjacent pair is a consecutive value - and with no filters enabled a 4-digit PIN has 10^4 = 10,000 equally likely codes.
Each digit position is filled independently with every digit 0-9 equally likely, which is what makes the result unpredictable: knowing part of the code tells you nothing about the rest, and earlier generations do not influence later ones. With no filters enabled, a length-n PIN has exactly 10^n possible values, and any particular code appears with probability 1 in 10^n.
Filters narrow the pool rather than bias the draw: with 'avoid repeated digits' on, codes such as 4418 or 1111 never appear, and with 'avoid sequential digits' on, codes containing adjacent consecutive values such as 12, 89, or 321 never appear. Codes that survive remain equally likely to one another; the only effect of a filter is that the surviving pool is smaller.
Against someone who knows you, usually yes - it contains no birth year, phone digit, or other personal anchor, and it avoids the 1234-style patterns people guess first. Against someone trying codes until one works, no: any 4-digit PIN has exactly 10,000 possibilities regardless of where it came from. Pick the longest length allowed and rely on the system's own attempt limiting.
No. With the repeated-digit filter off, 0000 has exactly the same chance as any other code - 1 in 10,000 for a 4-digit PIN. Uniform randomness throws up striking patterns occasionally; that is expected behavior, not a defect. Enable 'avoid repeated digits' if you want codes like that excluded.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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