Is Base64 encryption?

No. Base64 is an encoding scheme, not encryption. It provides no security — anyone can decode it. It's designed for data transport, not confidentiality.

Why does Base64 output end with = or ==?

The = characters are padding. Base64 processes input in groups of 3 bytes. If the input length isn't a multiple of 3, padding is added.

Does Base64 encoding increase file size?

Yes. Base64 encoding increases data size by approximately 33%. Three bytes of input produce four characters of output.

Can I Base64 encode binary files like images?

Yes. The binary data is read and each byte is encoded. This is commonly used for data URIs in HTML/CSS to embed small images inline.

Base64 Encode/Decode

Encode text to Base64 or decode Base64 back to text. Supports UTF-8.

Privacy: All calculations run entirely in your browser. No data is sent to any server.

Plain Text

Encode →← Decode

Base64

What is Base64 Encoding?

Base64 is a binary-to-text encoding scheme that represents binary data in an ASCII string format. It is designed to safely transmit binary data over text-based protocols such as HTTP, SMTP, and JSON. The name "Base64" comes from the 64-character alphabet used in the encoding: uppercase letters A–Z, lowercase letters a–z, digits 0–9, and the symbols + and /. During encoding, every group of 3 input bytes (24 bits) is split into four 6-bit values, each mapped to one of those 64 characters. Because 3 bytes of input produce 4 characters of output, Base64-encoded data is approximately 33% larger than the original binary.

How Base64 Encoding Works

The Base64 encoding process takes input bytes and divides them into groups of 6 bits. Each 6-bit group is then mapped to a corresponding character from the Base64 alphabet. When the input length is not evenly divisible by 3 bytes, padding characters (=) are appended to the output: one = is added when there are 2 remaining bytes, and == is added when there is 1 remaining byte. This ensures the encoded output length is always a multiple of 4 characters.

// Encode
const encoded = btoa("Hello, World!");
// "SGVsbG8sIFdvcmxkIQ=="

// Decode
const decoded = atob("SGVsbG8sIFdvcmxkIQ==");
// "Hello, World!"

// Handle UTF-8 strings
const utf8Encode = btoa(unescape(encodeURIComponent("Héllo")));
const utf8Decode = decodeURIComponent(escape(atob(utf8Encode)));

Common Use Cases

Data URIs: Embedding images directly in CSS or HTML using data:image/png;base64,... eliminates extra HTTP requests for small assets.
API Authentication: HTTP Basic Authentication encodes the username:password pair in Base64 before sending it in the Authorization header.
Email Attachments: MIME encoding relies on Base64 to embed binary attachments such as images and documents inside plain-text email messages.
JWT Tokens: The header and payload sections of JSON Web Tokens are Base64url-encoded, making them safe to include in URLs and HTTP headers.
Storing Binary in JSON/XML: When binary data must be embedded in text-only formats like JSON or XML, Base64 encoding provides a reliable text representation.

Base64 vs Base64url

Standard Base64 uses the characters + and / as part of its 64-character alphabet. However, both of these characters have special meaning in URLs and file systems: + is interpreted as a space in query strings, and / is a path separator. Base64url is a URL-safe variant that replaces + with - (hyphen) and / with _ (underscore). It also typically omits the trailing = padding characters since they are percent-encoded in URLs. Base64url is the encoding used in JSON Web Tokens (JWTs), URL query parameters, and anywhere the encoded string must be safe for use in a URI or filename.

Frequently Asked Questions

Is Base64 encryption?: No. Base64 is an encoding scheme, not encryption. It provides no security — anyone can decode it. It is designed for data transport, not confidentiality. Never use Base64 to protect sensitive data.
Why does Base64 output end with = or ==?: The = characters are padding. Base64 processes input in groups of 3 bytes. If the input length isn’t a multiple of 3, padding characters are added: one = for 2 remaining bytes, == for 1 remaining byte.
Does Base64 encoding increase file size?: Yes. Base64 encoding increases data size by approximately 33%. Three bytes of input produce four characters of output. This overhead is the trade-off for text-safe encoding.
Can I Base64 encode binary files like images?: Yes. This tool handles text encoding. For files, the binary data is read and each byte is encoded. This is commonly used for data URIs in HTML/CSS to embed small images inline.

Guides

Base64 Encode JSON Online Base64 Encode Image Online Base64url Encoding — URL-Safe Base64

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