Base64 encoder.

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.

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.

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.

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.

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.

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 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.

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.

No. The Base64 encoder is free and opens without a sign-in, an account or an install.

Nothing. The Base64 encoder holds your input in the page's memory, so closing or reloading the tab clears it, and it saves nothing in this browser.

The bar has one choice: Alphabet, standard (+ and /, padded with =) or URL-safe (- and _, no padding).

Base64 output is 4 characters for every 3 bytes, so about a third longer, and the status line under the result shows the bytes in, the characters out and the percentage.

The text is encoded as UTF-8 bytes first, so accented letters, other scripts and emoji round-trip through the decoder unchanged. Each of those characters takes more than one byte, which makes the output longer than the character count suggests.

Press Swap once there is a result and the same tool becomes the Base64 decoder, with the output moved into the input. The decoder shows the original text again.

Closest to the Base64 encoder: Base64 decoder, File to Base64, Base64 to file, Base32 encoder. Each opens on its own page, free and in the browser.

The Base64 encoder is one of 32 in its group. The group's page, /tools/encoding, lists them all.

The tool is free. Its interface is built from shadcn.io's own components (Button, Input, Slider and the rest of the registry under /ui), which come in React, Vue, Svelte and Solid. Pro adds the blocks and templates for the product around it.