Encode and decode Base64

A free online Base64 tool that runs in your browser. Paste text or Base64 into the left pane and the right pane updates as you type — auto-detect switches direction when your input looks like Base64. Two variants supported: standard (with + and /) and URL-safe (with - and _, no padding). File mode encodes any binary file into Base64; decoded binary output offers a Download button so non-UTF-8 payloads (images, archives, signatures) survive intact.

How to use

Pick a mode

Encode (text → Base64) or Decode (Base64 → text). Auto-detect handles the common case.

Paste your input

Left pane is your input. Output appears in the right pane in 200ms.

Optional: variant toggles

URL-safe and Strip = padding for JWT / URL embedding.

Copy or download

Copy to clipboard or save as a file.

Encode and decode Base64 with UTF-8 safety, URL-safe variant, and file support

URL-safe (- _ instead of + /) Strip = padding Auto-detect direction

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In: 0 Out: 0

Features

UTF-8 safe URL-safe variant Auto-detect direction File upload Binary-aware decode Whitespace tolerant

Common uses

Decode an Authorization Bearer Base64 token to inspect its contents.
Encode a small PNG into a data: URI for inline embedding.
Base64-encode credentials before sending in a Basic auth header.
Decode an email attachment's Base64 body to recover the file.

Why use this one

Most browser tools are wrapped in three layers of ads or use a server backend. This one is a single JavaScript file, runs auto-detect on every paste, handles UTF-8 + binary symmetrically, and supports the URL-safe variant out of the box.

Frequently asked questions

Free?

Yes — no account, no limits.

Why is the output 33% bigger?

Base64 uses 4 ASCII characters per 3 source bytes, so the encoded form is ~33% larger. The stats line shows the exact overhead.

What is URL-safe Base64?

A variant defined in RFC 4648 §5 that uses - and _ instead of + and /, and (often) drops the = padding. Used in JWT, OAuth state, and URL slugs.

Can I encode files?

Yes. Click "Encode a file…" to pick a file. Files up to your browser's memory work (typically 100 MB+).

How does auto-detect work?

When you paste into Encode mode, we check if the input matches the Base64 alphabet and length. If yes, we switch to Decode and show a toast.

Mobile?

Yes. Paste, copy, download — all work.

💡 Want us to improve this tool just for you?

We can — and it's free! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.

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Who is this tool for?

💻 Developers & IT Pros

Published 22 May 2026