stboxsandbox tools
All tools

Base64 & Base64URL Encoder/Decoder

Convert text and files between Plaintext, Base64, Base64URL, Hex, and Data URIs 100% in your browser.

Formatters & Utilities
Privacy: 100% Client-Side. Your data never leaves this browser tab. Processing uses Web APIs and client-side libraries only.

Edit any field — the others update live using UTF-8 TextEncoder / TextDecoder (no broken btoa on emoji).

What is Base64 encoding?

Base64 maps binary bytes to an ASCII alphabet so tokens, certs, and file blobs can travel safely in JSON, HTML, and HTTP headers. Base64URL (RFC 4648 §5) swaps +/ for -_ and often drops padding — the form JWTs and signed cookies use.

This converter keeps Plaintext, standard Base64, Base64URL, Hex, and percent-encoding in sync with UTF-8 TextEncoder/TextDecoder, and turns dropped files into data: URIs without uploading them.

How to use this tool

  1. Type or paste into any text field — the other formats update immediately.
  2. Switch to File → Base64 to drag an image, PDF, or cert and copy the data URI or raw Base64.
  3. Use Base64URL when working with JWTs; use standard Base64 for PEM bodies and most APIs.

Frequently asked questions

Why not use btoa() directly?

Native btoa throws on Unicode code points above 255. stbox encodes UTF-8 bytes first so emoji and accented text round-trip correctly.

Is my file uploaded?

No. File conversion reads ArrayBuffer in the browser and never sends bytes to stbox servers.

Where else does stbox use Base64?

JWT Workbench decodes Base64URL segments; SAML Inspector handles Base64 / Deflate-Base64 AuthnRequests; X.509 Decoder parses PEM Base64 certificate blocks.