Base64 Encoder & Decoder

Base64 turns arbitrary bytes, text or a whole image, into plain ASCII characters, so they survive being carried through systems built only for text.

Base64

A way to represent binary or text data using only 64 printable ASCII characters (A-Z, a-z, 0-9, +, /), plus = for padding. Common wherever raw bytes need to travel safely through a system built for text - email attachments, embedding a small image directly in HTML/CSS, API tokens, and more.

Standard vs. URL-safe (Base64url)

Standard Base64 uses + and / and pads with = - both characters have special meaning in a URL, so standard Base64 can't be dropped into a URL or filename as-is without encoding those characters again. URL-safe Base64 (RFC 4648) swaps + for -, / for _, and drops the = padding entirely - the variant JWTs and URL query parameters actually use.

Why decoding can fail

Not every string of text is valid Base64 - decoding fails if it contains a character outside the Base64 alphabet, or has the wrong length for its padding. This tool accepts either the standard or URL-safe alphabet when decoding, and ignores line breaks/whitespace (real Base64 is often wrapped at a fixed width), so most real-world Base64 pastes work without any cleanup first.

Images too, not just text

Switch to the Image tab to drop or upload an image (PNG, JPEG, GIF, WebP, or BMP) and get its ready-to-use Base64 Data URI - the exact string you can paste straight into an <img src="..."> or a CSS url(...). Pasting a Data URI, or a bare Base64 string that decodes to one of those formats, into that same tab is auto-detected in reverse - a real preview appears automatically, with the format, pixel dimensions, and file size shown. SVG isn't detected yet - it's a text/XML format, not one of the binary signatures this tool currently checks for.

Data URI

A self-contained string like data:image/png;base64,iVBORw0K... - the MIME type and the Base64-encoded bytes together in one value, with no separate file needed. Directly usable anywhere a URL is expected: an <img> tag's src, a CSS background-image, a JSON payload, and more.

Why this stays private

Encoding and decoding Base64 - text or images - doesn't need a server at all. Your browser already has everything required built in, including reading a dropped/uploaded file. Nothing you paste or upload here is ever sent anywhere.