Data URI Regex

Developer

Regular expression

/^data:[\w/+.-]+;base64,[A-Za-z0-9+/=]+$/

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

data:image/png;base64,AAAA

Should not match

image/png
not matching sample
data:image/png;base64,AAAA invalid
image/pngdata:image/png;base64,AAAA

Test cases

Input	Expected	Why it matters
`data:image/png;base64,AAAA`	Match	Representative valid input for this pattern.
`image/png`	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.
`data:image/png;base64,AAAA invalid`	No match	Common invalid or boundary input.
`image/pngdata:image/png;base64,AAAA`	No match	Common invalid or boundary input.

JavaScript

const re = /^data:[\w/+.-]+;base64,[A-Za-z0-9+/=]+$/;
re.test(input);

Python

import re
bool(re.search(r"^data:[\w/+.-]+;base64,[A-Za-z0-9+/=]+$", text))

PHP

$ok = preg_match('/^data:[\w\/+.-]+;base64,[A-Za-z0-9+\/=]+$/', $value) === 1;

Java

Pattern pattern = Pattern.compile("^data:[\\w/+.-]+;base64,[A-Za-z0-9+/=]+$");
pattern.matcher(value).find();

Go

re := regexp.MustCompile(`^data:[\w/+.-]+;base64,[A-Za-z0-9+/=]+$`)
ok := re.MatchString(value)

Notes and production use

Data URI 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.

Data URI