Base64 Encoding Explained: When, Why, and How to Use It

Base64 is one of those things every developer uses but few truly understand. Let's fix that. What Is Base64? Base64 is a binary-to-text encoding scheme that represents binary data using 64 ASCII characters (A-Z, a-z, 0-9, +, /). It's not encryption. It's not compression. It's just a way to represent binary data as text. Why Does Base64 Exist? Many systems were designed to handle text, not binary data. Email (SMTP), JSON, XML, HTML attributes, and URLs all expect text. Base64 bridges this gap. Common Use Cases 1. Data URIs in HTML/CSS <img src= "data:image/png;base64,iVBORw0KGgoAAAANSUhE..." alt= "icon" > .icon { background-image : url(data:image/svg+xml;base64,PHN2ZyB4bWxucz0i...) ; } When to use : Small icons (< 2KB) where reducing HTTP requests matters. When NOT to use : Large images. Base64 increases size by ~33%. 2. JWT Tokens JWTs use Base64URL encoding (replacing +/ with -_) for the header and payload: eyJhbGciOiJIUzI1NiJ9.eyJ1c2VyIjoiYWxpY2UifQ.signature 3. API Authentication Ba