Base64 Encoder & Decoder
Encode and decode Base64 strings instantly. Supports Unicode. All processing happens in your browser—no data sent to any server.
Base64 to Decode
Decoded Text
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What is Base64 Decoding?
Base64 decoding is the reverse of Base64 encoding. It converts an ASCII string composed of 64 printable characters (A–Z, a–z, 0–9, +, /) back into the original binary or text data. Base64 is commonly used to transmit binary data (like images, files, or certificates) over text-based channels such as email, JSON APIs, and HTML data URIs.
How Base64 Decoding Works
- Each Base64 character represents 6 bits of data
- Four Base64 characters decode into three bytes of binary data
- Padding characters (
=) indicate the end of the encoded data when the input length wasn't a multiple of 3 - The decoder maps each character back to its 6-bit value and reassembles the original binary stream
Common Use Cases
- Data URIs: Decode images embedded in HTML or CSS
- JWT Tokens: Decode JSON Web Token payloads for debugging
- Email Attachments: Decode MIME-encoded email content
- API Responses: Decode binary payloads from REST APIs
- Certificates: Decode PEM-encoded SSL/TLS certificates
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Frequently Asked Questions
What is Base64 decoding?
Base64 decoding converts a Base64-encoded string back into its original binary or text data. It reverses the Base64 encoding process, transforming the ASCII-safe representation back to the original content.
When do I need to decode Base64?
You need to decode Base64 when receiving data that was encoded for safe transmission over text-based protocols — such as embedded images in HTML/CSS (data URIs), email attachments (MIME), API responses with binary payloads, or JWT tokens.
Is my data sent to a server?
No. All decoding happens entirely in your browser using JavaScript. Your data never leaves your device, ensuring complete privacy and security.
Does it support Unicode?
Yes. The decoder handles UTF-8 encoded Base64 strings, so international characters, emoji, and special symbols are decoded correctly.
What if my Base64 string is invalid?
The decoder detects invalid Base64 input and shows a clear error message. Common issues include missing padding characters (=), illegal characters, or corrupted data.