Base64 Encoding: What It Is and When to Use It

Base64 Encoding: What It Is and When to Use It

Base64 converts binary data into ASCII text. It's not encryption — it's encoding. Anyone with the Base64 string can decode it back. Base64 is used when binary data needs to be in a text context:

How Base64 Works

Base64 takes 3 bytes of binary data (24 bits) and splits them into 4 groups of 6 bits. Each 6-bit group maps to a character in the alphabet A-Za-z0-9+/. = pads the end. This means every 3 bytes becomes 4 characters — a 33% size increase.

Common Use Cases

• Data URLs — data:image/png;base64,... embeds images in CSS/HTML without HTTP requests
• Email attachments — SMTP only handles text, so attachments are Base64-encoded
• JWT tokens — the payload in a JWT is Base64URL-encoded
• API keys in headers — Basic Auth sends user:pass as Base64

When NOT to Use Base64

• Image optimization — Base64 images in CSS increase HTML size by 33%. Large images should be loaded as files
• Security — Base64 is encoding, not encryption. Never use it to "hide" data
• Large files — 33% size overhead. Send binary via multipart upload instead