Free tool for developers
Base64 Encoder and Decoder — Convert Text and URL
Encode or decode text, URL parameters and data in Base64 format. Ideal for data URI, JWT, MIME email, Basic Authorization and CSS fonts. Everything is processed locally in the browser.
What is Base64 encoding and when is it used?
Base64 is a method of encoding binary data into an ASCII string. It is used when binary data needs to be transferred over protocols that only accept text (HTTP, email, JSON). Typical use cases: 1) Data URI for inline images in CSS and HTML, 2) Basic HTTP Authorization header, 3) MIME encoding of email attachments, 4) JWT (JSON Web Token) payload, 5) CSS @font-face for inline fonts, 6) JSON fields for small binary files. Base64 increases data size by ~33%, so it is not used for large files. Everything is processed locally in the browser — nothing is sent to the server.
- Encoding and decoding of text + URL parameters
- Local in the browser — without sending to the server
- Ideal for data URI, JWT, MIME email, Basic Auth
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Base64 Encoder & Decoder
Enter text, then encode to Base64 or decode from Base64.
Privacy: Everything is processed locally in the browser using the built-in btoa/atob functions. Your data is NOT sent to the server.
Where is Base64 used?
Six most common uses of Base64 encoding in web development.
Data URI images
Inline images in HTML and CSS without a separate HTTP request. Ideal for small icons and SVG files.
data:image/png;base64,iVBORw0KGgo...Basic HTTP Authorization
username:password encoded in Base64 is sent in the Authorization header for REST API authentication.
Authorization: Basic dXNlcjpwYXNzMIME email attachment
Binary email attachments (images, documents) are encoded in Base64 for SMTP transfer.
Content-Transfer-Encoding: base64JWT (JSON Web Token)
JWT header and payload are Base64URL encoded. Three segments separated by a dot.
eyJhbGciOiJIUzI1NiJ9.eyJ1c2VyIjoiam9obiJ9...JSON binary data
Small binary files (images, PDF) in JSON fields through REST/GraphQL APIs.
{"file": "SGVsbG8gV29ybGQ="}CSS inline fonts
@font-face with a Base64 encoded WOFF2 font — without additional HTTP requests.
@font-face { src: url(data:font/woff2;base64,...) }Base64 — how encoding and decoding works
Base64 is a group of binary-to-text encodings that represent binary data in ASCII format using 64 different characters: uppercase and lowercase letters (A-Z, a-z), numbers (0-9), and two special characters (+ and /). The = sign is used as padding at the end if the input is not divisible by 3 bytes.
The original binary data is divided into groups of 3 bytes (24 bits). These 24 bits are then split into 4 groups of 6 bits each, and each group is mapped to one Base64 character. This is why the resulting string is ~33% longer than the original.
Base64URL — variant for URL parameters
Standard Base64 uses the characters + and /, which have special meaning in URLs. The Base64URL variant replaces + with - and / with _ to avoid URL encoding. The padding character = is often omitted. The JWT format uses Base64URL for header and payload.
Although Base64 is often mistakenly presented as a form of encryption, it is NOT encryption — it is only encoding. Anyone can trivially decode a Base64 string. To protect sensitive data, use AES-256 encryption or HTTPS/TLS for transfer.
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