Base64 Encode & Decode — Free Online

What Is Base64 Encoding?

Base64 is an encoding scheme that converts binary data (or text) into a string of 64 ASCII characters. It was designed to allow binary data to be safely transmitted over systems that only handle text — like email protocols (SMTP), XML files, and early internet APIs. The name comes from the 64-character alphabet it uses: A-Z, a-z, 0-9, and + and /.

When to Use Base64 Encoding

• Embedding images directly in HTML or CSS as data URIs (src="data:image/png;base64,...")
• Encoding authentication credentials for HTTP Basic Auth headers
• Storing binary data (like images or PDFs) in JSON or XML fields
• Encoding data to pass in URL query parameters safely
• Working with APIs that accept file uploads as Base64 strings
• Email attachments — MIME encoding uses Base64 for attachments

Base64 vs URL Encoding

Base64 encodes binary data to ASCII text. URL encoding (percent-encoding) makes text safe for use in URLs by replacing special characters with % sequences. They solve different problems — use Base64 for binary data, URL encoding for query string values. Compressfy has a separate URL Encoder/Decoder tool for URL encoding tasks.

Base64 Size Overhead

Base64 encoded data is approximately 33% larger than the original. A 100KB image becomes ~133KB when Base64 encoded. This is important to consider when deciding whether to embed images as Base64 or load them as separate files in web applications.