Base64 Converter
Encode or decode strings to/from Base64. (Unicode supported)
How to Use Base64 Converter
Input Text
Enter either plain text to encode or a Base64 string to decode in the left area.
Select Mode
Choose the 'Encode' or 'Decode' radio button at the bottom-left.
Execute Convert
Results appear instantly on the right and can easily be copied.
💡 Practical Base64 Tips
Create Data URI
Encode small images or resources into Base64 and embed them directly in HTML/CSS to speed up loading times.
Decode API Tokens
Easily check internal information like expiration by decoding the payload of tokens such as JWT.
No Special Char Issues
It perfectly supports Unicode and emoji, meaning you can safely transmit data without data corruption over URLs.
Encoding isn't encryption
Since Base64 is merely an encoding scheme and not encryption, it shouldn't be used to protect sensitive data.
⚙ Technical Principle: The Base64 Alphabet and 6-Bit Encoding
Base64 is an encoding system that uses exactly 64 characters: A-Z (26), a-z (26), 0-9 (10), plus + and / (2) — all safe ASCII characters. Since 64 equals 2⁶, each Base64 character represents exactly 6 bits of binary data.
The conversion works by grouping raw binary data into 3-byte (24-bit) blocks, then splitting each block into four 6-bit groups. Each 6-bit group maps to a character in the Base64 alphabet. This means 3 bytes of data become 4 ASCII characters — a ~33% size increase over the original. This is why Base64-encoded images and files are larger than the originals.
Base64URL replaces + with - and / with _ for safe use in URLs without percent-encoding. JWT (JSON Web Tokens) and OAuth 2.0 tokens use this Base64URL variant.
🔒 Privacy Architecture: Complete Local Processing of Sensitive Binary Data
When Base64-encoding or decoding API keys, JWT tokens, or certificate data using an online tool, that sensitive content can be exposed to external servers. Decoded JWT tokens directly reveal user information and permission data, making this a critical security risk.
Following the Zero-Server Principle, HeeyaTools Base64 Converter handles all encoding/decoding through the browser's built-in btoa()/atob() APIs and JavaScript. None of your tokens, keys, or text data is ever transmitted to a server.
However, always remember: Base64 is encoding, not encryption. Anyone can instantly decode Base64-encoded data. For true security, combine Base64 with AES-256 or RSA encryption.
📚 Industry Insight: The Birth of Base64 and Its Role in the Modern Web
Base64 was born in 1987 as part of the MIME email standard (RFC 2045). Early email systems could only transmit pure ASCII text, so sending images or attachments required converting binary data into ASCII — the origin of Base64.
Today, Base64 underpins multiple core web technologies: Data URIs (data:image/png;base64,...) embed images directly in HTML/CSS; JWT encodes its header and payload in Base64URL for API authentication; and HTTP Basic Authentication transmits credentials as Base64-encoded ID:password in the Authorization header.
More recently, Base64 is widely used for exchanging WebAssembly (Wasm) modules with JavaScript, and for sending images directly to AI model APIs (GPT-4V, Claude Vision, etc.) as Base64-encoded strings in request bodies.