Base64.sh

What is Base64 encoding and why is it used?

Base64 is a binary-to-text encoding scheme that converts binary data into ASCII text format using 64 printable characters. It's commonly used for embedding images in HTML/CSS, sending binary data through email, API data transfer, and storing binary data in text-based systems.

How do I decode Base64 online?

Paste the Base64 string into the INPUT area and click [DECODE]. The decoded text appears instantly in the OUTPUT area. The decoder auto-detects URL-safe Base64 and missing padding. Everything runs locally in your browser, so you can safely decode tokens and confidential API payloads without sending them to any server.

How do I encode text to Base64?

Type or paste the plain text into the INPUT area and click [ENCODE]. The Base64 output appears instantly. Use the --url-safe option to produce URL-safe Base64 (required for URLs and filenames), and --no-pad to drop the trailing = characters. The encoder handles full UTF-8, so emoji and non-Latin text encode correctly.

What does the Base64 alphabet look like?

Standard Base64 uses A-Z, a-z, 0-9, +, and / — 64 printable ASCII characters, plus = for padding. URL-safe Base64 (RFC 4648 §5) replaces + with - and / with _ so the output is safe to use in URLs and filenames. Every 3 bytes of input become exactly 4 Base64 characters; padding fills in when the input length is not a multiple of 3.

What is Base64 padding and can I remove it?

Base64 padding is the = character appended to make the output length a multiple of 4. A 1-byte input produces XX==, a 2-byte input produces XXX=, and a 3-byte input needs no padding. Most decoders accept unpadded input as long as the length is otherwise valid — standards like JWT and URL-safe Base64 omit padding by convention.

How do I encode or decode Base64 in code?

Every major language has a built-in Base64 library: JavaScript — btoa(str) / atob(str) (wrap with TextEncoder/TextDecoder for UTF-8); Node.js — Buffer.from(str).toString('base64'); Python — base64.b64encode / base64.b64decode; PHP — base64_encode / base64_decode; Shell — echo -n "hello" | base64 and echo "aGVsbG8=" | base64 -d; Go — base64.StdEncoding.EncodeToString.

What is a Base64 data URI?

A data URI embeds a Base64-encoded resource directly in HTML, CSS, or JSON using the format data:[mime-type];base64,[payload]. For example, data:image/png;base64,iVBORw0KGgo... embeds a PNG image inline with no separate HTTP request. Data URIs are useful for tiny icons and fonts where the round-trip cost exceeds the encoded size overhead (~33%).

Why does my Base64 decode to garbled text or fail?

Common causes include invalid characters (whitespace or non-alphabet characters), missing padding, mixing URL-safe and standard Base64, values that were also URL-percent-encoded or quoted-printable before Base64, or decoding a binary payload as UTF-8 text. For binary payloads like PNG files, save the decoded bytes to a file instead of viewing as text.