You have probably copied a Base64 string a hundred times without thinking about it. That long chain of letters and slashes at the end of a JWT. The data:image/png;base64, blob in a CSS file. The Authorization: Basic header in a Postman collection.
Base64 is everywhere in a developer's daily work — and most developers have a fuzzy mental model of what it actually does. This article clears that up, and covers the five real production use cases where you will encounter it.
What is Base64 and why does it exist?
Base64 converts binary data into a string of 64 printable ASCII characters: the letters A–Z and a–z, digits 0–9, plus + and /. The name literally describes the alphabet size.
The reason it exists: many systems that move data were designed for text only. Email protocols (SMTP), HTML attributes, JSON payloads, XML documents, HTTP headers — all of these were built around the assumption that data is readable ASCII text. Raw binary bytes can corrupt or break these systems.
