Base64 Encoder & Decoder

Encode text to Base64, or decode a Base64 string back to plain text. Runs entirely in your browser.

Input

What is Base64?

Base64 is a way of representing binary or text data using only 64 printable characters (A-Z, a-z, 0-9, +, /). It's not encryption — anyone can decode it instantly — but it's useful for safely embedding data in places that only accept plain text, like URLs, JSON, or email attachments.

Common uses

Embedding small images directly in HTML or CSS as a data URL
Passing binary-ish data through systems that only handle text, like some APIs
Quickly inspecting what a Base64 string in a config file or token actually says

Worked examples

Hello, World! encodes to SGVsbG8sIFdvcmxkIQ==. Accents and other scripts are handled by converting to UTF-8 first, so café becomes Y2Fmw6k= and 日本 becomes 5pel5pys. Every 3 bytes become 4 characters, which makes the output about a third longer, and the equals signs pad the end: a is YQ==, ab is YWI= and abc is YWJj.

How decoding behaves

Spaces and line breaks in the input are ignored, and missing padding is accepted, so SGVsbG8 decodes to Hello.
Only the standard alphabet works. The URL-safe variant used inside tokens, with - and _ instead of + and /, produces an error until you swap those characters back.
The decoded bytes are read as UTF-8 text. If the data is not text, such as an image, you will see replacement characters rather than an error message.
Anything that is not valid Base64, or whose length cannot be valid, shows an error.

Good to know

Base64 is an encoding, not protection: it hides nothing from anyone who looks. It is also a text converter only. To turn a picture into a data URL use the Image to Base64 tool, and to read the readable parts of a login token use the JWT Decoder, which handles the URL-safe form.

Guide

Base64 Explained: Why It's 33% Larger — How Base64 works, why it adds about a third to the size, why it isn't encryption, and how Base64URL differs.

Frequently asked questions

Is Base64 the same as encryption?

No — Base64 is just a different way of representing the same data as plain text characters. Anyone can decode it instantly; it provides no security or privacy on its own.

Why did decoding fail with an error?

The input contained characters outside the standard Base64 alphabet (A-Z, a-z, 0-9, +, /, and = for padding) or had an impossible length. The most common cause is URL-safe Base64, which uses - and _; swap them for + and / and try again. Spaces and line breaks are ignored and don't cause errors.

Why is the encoded text longer than the original?

Base64 turns every 3 bytes into 4 characters, so the result is roughly a third larger, plus padding. That is the price of using only safe printable characters.

Why do I see strange characters after decoding?

The decoded bytes are shown as UTF-8 text. If the original data was binary, such as an image or a compressed file, it can't be shown as readable text and appears as replacement characters.

Can I decode the parts of a JWT here?

Only after converting them. Tokens use the URL-safe alphabet, so replace - with + and _ with /, or use the JWT Decoder, which does it for you.