JavaScript Atob_btoa Guide
atob and btoa convert between Base64 and binary data for data URIs, Basic auth headers, and JWT tokens. The guide walks through Encoding & Decoding. `btoa(str)` — encode to Base64. `atob(enc)` — decode. Works with ASCII only. Handle Unicode: `btoa(encodeURIComponent(str))`. Uses: data URIs `data:image/png;base64,...`, Basic Auth `btoa(user+":"+pass)`. Not encryption — encoding only. The guide is organized into 1 sections that build on each other, each pairing a prose explanation with runnable code. Related guides: Arrays, Strings, Numbers, Math, Date. This is one of 145 JavaScript guides on JS Reference — see the full list on the guides page. Practice what you learn in the JavaScript playground, and look up any unfamiliar term in the JavaScript glossary.