Base64 Encoder & Decoder

Encode text to Base64 or decode Base64 back to plain text — all in your browser, nothing sent to a server.

Plain Text to Encode

URL-safe Base64 (+→-, /→_, strip =)

Base64 Output

Base64 to Decode Decoded Output

Frequently Asked Questions

Base64 is a binary-to-text encoding scheme that represents binary data using 64 ASCII characters (A–Z, a–z, 0–9, + and /). It is widely used to embed binary data (images, files) in text-based formats like HTML, CSS, JSON, and email (MIME).

Standard Base64 uses + and /, which have special meanings in URLs. URL-safe Base64 replaces + with - and / with _, and strips padding = signs. It is used in JWT tokens and OAuth parameters.

No. Base64 is an encoding scheme, not encryption. Anyone who sees Base64-encoded data can trivially decode it. Do not use Base64 to protect sensitive information.

How Base64 Encoding Works

Base64 converts arbitrary binary data into a stream of printable ASCII characters using a 64-character alphabet.

Group Bytes

The input is read as raw bytes and grouped into chunks of 3 bytes (24 bits). Each group is split into four 6-bit values.

Map to Characters

Each 6-bit value (0–63) maps to a character in the Base64 alphabet: A–Z (0–25), a–z (26–51), 0–9 (52–61), + (62), / (63).

Pad Output

If the input length isn't divisible by 3, padding characters (=) are added to make the output a multiple of 4 characters. URL-safe mode replaces + with - and / with _.

Common Use Cases

HTTP Basic Authentication

The Authorization: Basic header encodes username:password as Base64. Paste the header value here to decode credentials during API debugging (over HTTPS only).

Data URIs

Small images, fonts, and SVGs are embedded directly in HTML/CSS as Base64 data URIs (data:image/png;base64,…), eliminating extra HTTP requests for small assets.

JWT Token Inspection

JSON Web Tokens are Base64URL-encoded. Paste the second segment (payload) to decode it and read the claims — useful for debugging auth flows without a dedicated JWT tool.

Email MIME Attachments

Email attachments in MIME format are Base64-encoded to transport binary files as text. If you've ever seen long strings in raw email source, they're often Base64-encoded file data.

Binary Data in JSON APIs

JSON has no native binary type. Base64 is the standard workaround: images, PDFs, and byte arrays are serialized as Base64 strings before being sent in JSON request or response bodies.

Cryptographic Key Transport

PEM-formatted certificates and private keys are Base64-encoded DER structures wrapped in -----BEGIN…----- headers. Understanding the encoding helps when working with TLS/SSL certificates.