Data URI (Base64) Regex for PHP

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching data uri (base64), ported and verified for PHP. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your PHP project — whether you're validating in a Laravel validator, a WordPress plugin, or a standalone PHP script.

Php Implementation

<?php
// Data URI (Base64)
// ReDoS-checked | RegexVault — Web & Network > URL

define('DATA_URI_BASE64_PATTERN', '/^data:([a-zA-Z][a-zA-Z0-9!#$&\-^_]{0,59}\/[a-zA-Z][a-zA-Z0-9!#$&\-^_+.]{0,59});base64,([A-Za-z0-9+\/]{4})*([A-Za-z0-9+\/]{2}==|[A-Za-z0-9+\/]{3}=)?$/');

function validate_data_uri_base64(string $input): bool {
    return (bool) preg_match(DATA_URI_BASE64_PATTERN, $input);
}

// Example
var_dump(validate_data_uri_base64("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg==")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > URL category and has been checked for ReDoS risk. That matters for PHP developers because especially relevant in PHP where PCRE backtracking limits can trigger silent failures on malicious input. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Base64 padding (= or ==) is structurally validated. The MIME type is captured in group 1. Maximum practical data URI size is ~2MB for browser compatibility.