Online base64_encode, base64_decode

Base64 is a way to write any binary data (text, an image, an archive) using only "safe" characters: Latin letters A–Z, a–z, digits 0–9 and the signs + and /. This online base64_encode and base64_decode tool encodes a string to Base64 and decodes it back right in your browser; the text is not sent anywhere.

How it works

The data is split into groups of 3 bytes (24 bits), each group into 4 parts of 6 bits, and each part is replaced with a character from a 64-symbol alphabet. If bytes are missing at the end, the result is padded with =.

Why the result is a third larger

3 bytes become 4 characters, so encoded data is about 33% larger than the original (plus possible line breaks). Base64 is convenient for transport, not for saving space.

Examples

URL-safe variant (base64url)

The characters + and / have special meaning in URLs, so there is a base64url variant: + becomes -, / becomes _, and the trailing = is usually dropped. For example, the bytes FB FF BF are +/+/ in standard Base64 and -_-_ in base64url.

Where it is used

• data: URIs — images and fonts directly in HTML and CSS: data:image/png;base64,iVBORw0...
• Email attachments — the MIME standard sends files in emails as Base64.
• JWT — the token header and payload are base64url-encoded and can be decoded and read.
• HTTP Basic authentication — the header Authorization: Basic dXNlcjpwYXNz carries "user:pass" in Base64.
• APIs and JSON — sending files and binary fields where only text is allowed.

Good to know

• Base64 is NOT encryption. Anyone can decode the string in a second. Do not store passwords or secrets this way: Basic auth and JWT are safe only over HTTPS and with a signature.
• Text is converted to UTF-8 bytes before encoding, so Cyrillic takes twice as many characters as Latin.
• Spaces and line breaks inside Base64 are usually ignored when decoding, while other stray characters cause an error.
• In PHP use base64_encode() / base64_decode(); in JavaScript btoa() / atob() (Latin-1 only) or Buffer in Node.js.

How to use the page

• Type text into the source field — Base64 appears in the result field.
• Or paste Base64 into the result field — the source text is decoded automatically.
• The copy button puts the result on the clipboard.