Number Regex

Extraction

Regular expression

/[-+]?\d*\.?\d+(?:[eE][-+]?\d+)?/

Pattern breakdown

Part	Meaning
`Anchor or context`	Use anchors when you need whole-string validation.
`Main token`	The core token sequence describes the accepted text shape.
`Character class`	Character classes limit which characters are valid.
`Quantifier`	Quantifiers control how many characters or groups are accepted.
`Flags`	Use language-specific flags such as i, m, or u only when needed.

Should match

-12.5e3

Should not match

abc
not matching sample
-12.5e3 invalid
abc-12.5e3

Test cases

Input	Expected	Why it matters
`-12.5e3`	Match	Representative valid input for this pattern.
`abc`	No match	Common invalid or boundary input.
`(empty string)`	No match	Common invalid or boundary input.
`not matching sample`	No match	Common invalid or boundary input.
`-12.5e3 invalid`	No match	Common invalid or boundary input.
`abc-12.5e3`	No match	Common invalid or boundary input.

JavaScript

const re = /[-+]?\d*\.?\d+(?:[eE][-+]?\d+)?/;
re.test(input);

Python

import re
bool(re.search(r"[-+]?\d*\.?\d+(?:[eE][-+]?\d+)?", text))

PHP

$ok = preg_match('/[-+]?\d*\.?\d+(?:[eE][-+]?\d+)?/', $value) === 1;

Java

Pattern pattern = Pattern.compile("[-+]?\\d*\\.?\\d+(?:[eE][-+]?\\d+)?");
pattern.matcher(value).find();

Go

re := regexp.MustCompile(`[-+]?\d*\.?\d+(?:[eE][-+]?\d+)?`)
ok := re.MatchString(value)

Notes and production use

Number regex is useful as a practical starting point. Test it against your real input, avoid using it as the only security control, and prefer a parser when the format has complex grammar.

Performance tip: avoid running complex regular expressions repeatedly on very large untrusted strings without limits. Prefer anchored validation patterns, cap input length before matching, and use a parser when the target format has nested grammar.

Number