Overview
Introduction
This tool turns a plain list of integers into a regular expression that matches exactly those values and nothing else.
Enter one integer per line, and it builds an anchored alternation pattern like "^(3|17|42)$" that you can drop straight into validation code.
What Is Integer to Regex Generator?
A generator that converts a set of integers into a regex using literal alternation: each distinct value becomes one branch of a "|"-separated group, wrapped in "^(...)$" anchors.
It's the inverse of a manual regex-writing task: instead of hand-typing a pattern for a fixed set of allowed numbers, you list the numbers and get the pattern.
How Integer to Regex Generator Works
Each non-blank input line is parsed as an integer; invalid lines are rejected with a clear error.
Duplicate values are removed while preserving first-seen order.
The remaining values are joined with "|" and wrapped as "^(...)$" so the pattern matches a full string equal to exactly one of the listed integers.
When To Use Integer to Regex Generator
Use it when you need to validate that user input is one of a small, fixed set of allowed numeric codes (e.g. status codes, category IDs).
It's also useful for quickly turning a spreadsheet column of allowed values into a regex for a config file or validation library.
Often used alongside Regex to Integer Generator and Integer Filter.
Features
Advantages
- Guarantees the resulting regex matches exactly the listed set, no more and no fewer values.
- Simple, predictable output structure that's easy to review or diff.
- Deduplicates repeated input values automatically.
Limitations
- Not range-optimized: a long consecutive run like 1 through 100 produces 100 separate alternation branches rather than a compact quantified pattern.
- Capped at 500 input values to keep the generated pattern a reasonable size.
- Does not validate that the resulting pattern is efficient for very large alternations in a particular regex engine.
Examples
Best Practices & Notes
Best Practices
- Keep the input list to the exact set you want to allow; anything not listed will not match.
- Remove the ^ and $ anchors if you need the pattern to match a number as a substring within a longer string.
Developer Notes
Input lines are validated against /^-?\d+$/, deduplicated via a Set while preserving first-seen order, then joined with "|" and wrapped in "^(...)$"; this is a literal-alternation encoder, not a range-collapsing or NFA-minimizing regex builder.
Integer to Regex Generator Use Cases
- Validating that a form field's value is one of a small fixed set of allowed numeric codes
- Turning a spreadsheet column of allowed IDs into a config-file regex
- Quickly building a test regex fixture for a known set of values
Common Mistakes
- Expecting the tool to compress consecutive runs into a range pattern; it lists every value individually.
- Including a non-integer line, which is rejected with a clear error rather than silently skipped.
- Forgetting the anchors mean the pattern requires an exact full-string match, not a substring match.
Tips
- Pair this with the Regex to Integer Generator to double-check the pattern by generating sample matches from it.
- For very large sets, consider a range-based regex instead if consecutive runs dominate your list.