Base64 encoding converts binary data into a text string using only 64 safe characters (A-Z, a-z, 0-9, +, /). It's not encryption - it's a way to make sure binary data survives transport through systems that were designed for text.

For example, email was originally designed for plain text. If you send a photo as an email attachment, the email system uses Base64 to convert the photo's binary data into text that won't get corrupted in transit.

How It Works (Briefly)

Every three bytes (24 bits) of data are split into four 6-bit groups. Each 6-bit group maps to one of 64 characters in the Base64 alphabet. The result is about 33% larger than the original, but it's guaranteed to pass through any text-based system without corruption.

When Developers Use Base64

  • Data URLs - Embed small images or fonts directly in HTML/CSS. Instead of <img src="icon.png">, you use <img src="data:image/png;base64,...">. This saves an HTTP request.
  • Email attachments - SMTP can only handle 7-bit ASCII. Base64 lets you attach PDFs, photos, and other binary files.
  • API authentication - HTTP Basic Auth sends usernames and passwords as Base64-encoded strings in the header.
  • Storing binary in JSON - JSON is a text format. Base64 lets you include binary data like thumbnails or encrypted blobs in a JSON payload.

What Base64 Is NOT

Base64 is not encryption. Anyone can decode Base64 instantly. If you need to keep data secret, encrypt it first (with AES, for example), then encode the encrypted result as Base64 for transport.

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