Base64 writes binary data with 64 printable characters: A to Z, a to z, 0 to 9, + and /, with = as padding. It dates from the PEM mail standard of 1987, was fixed in MIME in 1993 and is specified in RFC 4648. It exists so that bytes can travel through systems built for text, such as email and JSON.

How does Base64 encoding work?

Three bytes are 24 bits, split into four groups of six bits, each written as one of the 64 characters. The output is a third larger than the input. When the input isn't a multiple of three bytes, the last group is padded with one or two = characters so the length is a multiple of four.

What is Base64 used for?

Email attachments (MIME), data URLs in HTML and CSS, JSON Web Tokens, HTTP Basic authentication headers, images inlined in stylesheets, binary fields in JSON and XML, and the SSH and PEM key files on every developer's machine.

Not the standard alphabet: + and / have meanings in a URL and = is reserved, so they have to be percent-encoded. The URL-safe variant from RFC 4648 §5 swaps them for - and _ and usually drops the padding; JWTs and most web APIs use it. The encoder here offers both.

How does Base64 compare to the other encodings?

It is the default for a reason: a third larger than the bytes, where hex doubles them and Base85 adds a quarter; built into every language and browser (btoa, atob, Buffer); and understood by every protocol. Pick Base32 when case can't be trusted, Base58 for things people copy by hand, Base85 only where PDF or PostScript asks for it.

Can Base64 be used for encryption?

No. Base64 is an encoding, not encryption: it changes how bytes are written, not who can read them, and anyone can decode it with no key. Encrypt first (AES, age, a library's sealed box) when the content needs protecting, then encode the ciphertext if it has to travel as text.

How do I encode text to Base64?

Type or paste into the input and the Base64 appears as you type: "Man" becomes TWFu. Text is encoded as UTF-8 bytes, so accents and emoji come out the same as in every language's standard library. Copy the result, download it as a text file, or press Swap to decode it back.

Drop a file onto the input or choose one with the button, and its bytes are encoded directly, not as text. Any file the browser can hold in memory works; a few hundred megabytes is fine, and the result is a third larger.

Standard or URL-safe: which should I use?

Standard Base64 uses + and / and pads with = to a multiple of four characters: the form for email, data URLs and most APIs. URL-safe Base64 (RFC 4648 §5, "base64url") uses - and _ instead and leaves the padding off, so it can sit in a URL, a file name or a JWT without escaping. The decoder reads both.

Is my text or file uploaded anywhere?

Nothing leaves your browser. The text or file is read into memory on your machine and the encoding is computed there, in plain JavaScript; the page makes no request with it. Load the page, go offline and it keeps working.

Base64 encoder.

Type text or drop a file and read its Base64 as you type. Standard or URL-safe alphabet, copy or download the result; everything runs in your browser.64 characters+33% size4:3 characters to bytes0 bytes uploaded

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How it works

3 steps, no account. It runs in your browser and nothing is uploaded.

Enter text or a file
Type or paste anything, or drop a file onto the input; the Base64 updates with every keystroke.
Choose the form
Standard or URL-safe: which should I use: pick in the bar and the result is rewritten in place.
Copy, download or swap
Copy the Base64, download it as a text file, or press Swap to decode it back.

Where Base64 is used

A third larger than the bytes, and understood everywhere: the default. Where Base64 does its work.

JSON Web Tokens
A header, a payload and a signature, each base64url-encoded and joined with dots: the token every OAuth flow hands around.
Data URLs
An image written straight into HTML or CSS as `data:image/png;base64,…`, saving a request at the cost of a third more bytes.
Email attachments
MIME writes every attachment as Base64 lines of 76 characters, because the mail protocols only promise to carry 7-bit text.
HTTP Basic auth
`Authorization: Basic` carries `user:password` as Base64. Encoding, not encryption, which is why it needs TLS.
Binary in JSON
JSON has no byte type, so a protobuf blob, a public key or a thumbnail travels in a string field as Base64.
PEM files
PEM certificates and keys are DER bytes as Base64 between `-----BEGIN` and `-----END` lines.
Everywhere
`btoa` and `atob` in every browser, `Buffer.from(s, "base64")` in Node, `base64` on the command line.
Integrity and secrets
A script tag's integrity attribute is a hash in Base64; Kubernetes secrets are Base64 in YAML.

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For personal projects & open source

$32instead of $49/mo

$389 billed yearly

How many people can use the license.Seats: 1 seat
Client work, SaaS products and anything you charge for.Commercial use: Personal & open source only
Production-ready React sections: hero, pricing, features, dashboards and more.Pro blocks: 6,000+ blocks
Complete multi-page sites you can ship as they are.Templates: All 14 templates
React icons from every major library, installable with one command.React icons: 294k+ icons
Presets that restyle every block, in light and dark.Themes: All 59 themes
Lets your AI editor search, preview and install blocks for you.MCP server: Basic usage
Priority requests are answered first.Support: Standard

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Base64 encoder.

Base64 encoder.

How it works

Enter text or a file

Choose the form

Copy, download or swap

Where Base64 is used

JSON Web Tokens

Data URLs

Email attachments

HTTP Basic auth

Binary in JSON

PEM files

Everywhere

Integrity and secrets

Related tools

Build it with Pro

Individual

Team

Organization

Individual

Team

Organization

Questions and answers

What is Base64?

How does Base64 encoding work?

What is Base64 used for?

Is Base64 URL-safe?

How does Base64 compare to the other encodings?

Can Base64 be used for encryption?

How do I encode text to Base64?

Can I encode a file?

Standard or URL-safe: which should I use?

Is my text or file uploaded anywhere?

Build the product around it