Base64 String Converter

Free online tool. All processing is client-side. No signup needed.

How to Use the Base64 String Converter

1. Enter your input values above
2. Results update automatically
3. Copy or download the output

What is a Base64 String Converter?

A Base64 String Converter encodes plain text into Base64 and decodes Base64 back to readable text. Base64 encoding converts binary data (or any text) into a limited set of 64 ASCII characters (A-Z, a-z, 0-9, +, /), making it safe for transmission through systems that only support text, such as email (MIME), JSON payloads, URL parameters, and data URIs. Base64 is everywhere in modern computing: embedding images in HTML/CSS (data:image/png;base64,...), storing binary in databases, transmitting files in APIs, and encoding credentials in HTTP Basic Authentication headers.

How Does It Work?

The encoding process takes 3 bytes (24 bits) of input and splits them into 4 groups of 6 bits. Each 6-bit group maps to one of 64 characters. If the input length isn't a multiple of 3, padding characters (=) are added. Decoding reverses the process. Our tool handles both standard Base64 and URL-safe Base64 (replacing +/ with -_ and omitting =).

Formula

Base64 Encoding:\n1. Convert text to bytes (UTF-8)\n2. Take 3 bytes (24 bits) at a time\n3. Split into 4 × 6-bit groups\n4. Map each 6-bit value to Base64 alphabet (0-25=A-Z, 26-51=a-z, 52-61=0-9, 62=+, 63=/)\n5. Add = padding if input not multiple of 3 bytes\n\nSize Increase: ~33% (3 bytes → 4 characters)\n\nURL-Safe variant: + → −, / → _, = omitted\nMIME variant: line breaks every 76 characters

Who Uses This Tool?

• Developers encoding credentials for HTTP Basic Authentication headers
• Web developers embedding small images as Base64 data URIs in CSS/HTML
• API developers encoding binary data for JSON payload transmission
• Email systems encoding attachments via MIME Base64
• Debugging Base64 strings found in code, config files, or network requests

Pro Tips

• Base64 is encoding, NOT encryption. Anyone can decode it — never use Base64 to 'protect' sensitive data
• Base64 increases data size by ~33%. For large data, consider alternatives: gzip compression before Base64, or direct binary transmission if the protocol supports it
• For URL parameters, use the URL-safe variant which replaces +/ with -_ and omits =. Standard Base64's + and / characters cause issues in URLs
• If you see Base64 strings that won't decode, check for: (1) URL-safe chars that need converting back, (2) missing padding = at the end, (3) embedded newlines or spaces

Frequently Asked Questions about Base64 String Converter

Is Base64 encryption?

No. Base64 is encoding — a reversible transformation with no key. It provides zero security and can be decoded by anyone. Use proper encryption (AES-GCM, ChaCha20-Poly1305) for securing data.

Why does Base64 exist?

Many protocols (email, HTTP, JSON) are text-only and can't handle raw binary data. Base64 converts binary into 'safe' text characters that survive transmission through any text-based system.

Free online Base64 String Converter — no signup, 100% client-side processing. All data stays in your browser.