Regex for Taiwan ID number
1 letter + 9 digits, Taiwanese national ID.
The Taiwan ID number regex is ^[A-Z][12]\d{8}$ — copy it below, or open it in the explainer for a token-by-token breakdown.
The pattern
^[A-Z][12]\d{8}$
What it matches
A123456789B287654321Z199999999
What it doesn't match
a123456789A323456789AB12345678
Notes & gotchas
Format: 1 letter (region of issue: A=Taipei, B=Taichung, etc.) + 1 digit indicating gender (1=male, 2=female) + 8 digits including a check digit. For ARC (foreigners) the second char is also a letter.
Code in your language
Use the explainer's Code tab to generate ready-to-paste snippets in JavaScript, Python, Java, .NET, Go, Ruby, and PHP for this pattern.
Open in explainer →Token-by-token breakdown
Every part of the pattern, left to right:
| Token | Meaning |
|---|---|
^ | start of string (or line in multiline mode) |
[A-Z] | any of: uppercase letters |
[12] | any of: “1”, “2” |
\d{8} | exactly 8 times: digit (0–9) |
$ | end of string (or line in multiline mode) |
About this pattern
Country-specific identifier formats vary widely. The pattern below validates structure; many real IDs include checksums that regex can't verify. For high-stakes use, validate against the issuing authority.
Quick usage in different languages
This exact pattern — with the correct escaping and idioms for each language:
- JavaScript:
/^[A-Z][12]\d{8}$/.test(value) - Python:
re.match(r"^[A-Z][12]\d{8}$", value) - Java:
Pattern.compile("^[A-Z][12]\\d{8}$").matcher(value).matches() - C# / .NET:
Regex.IsMatch(value, @"^[A-Z][12]\d{8}$") - Go:
regexp.MustCompile(`^[A-Z][12]\d{8}$`).MatchString(value) - Ruby:
/^[A-Z][12]\d{8}$/.match?(value) - PHP:
preg_match('~^[A-Z][12]\d{8}$~', $value)
The explainer’s Code tab regenerates these for any pattern you paste, and the downloadable cheat sheet bundles the breakdown, all seven snippets, and the pitfalls below onto one printable page.
Common pitfalls
- Anchored to the whole string. This pattern uses ^ and $, so it requires the entire input to match. To find it inside a longer text, drop the anchors and use the global (g) flag.
- Uppercase only. Ranges like [A-Z] won't match lowercase. Add a-z (or the i flag) if lowercase input should be accepted.
- Escape it correctly per language. In Java and JavaScript strings each backslash must be doubled (\\d); in Python, Go, and C# use raw/verbatim strings so the backslashes survive.
- Validate beyond format. Matching the format doesn't guarantee the value is real. Confirm the taiwan id number against a source of truth (database, API, or checksum) where it matters.
Related patterns
More patterns in the Other regional category:
See also
Browse all 300 patterns in the library, or open this regex in the interactive explainer to see a token-by-token breakdown, test against custom input, and generate code in seven languages.