Is Base64 encryption?

No. Base64 is a reversible encoding meant to make binary data text-safe, not to protect it. Anyone can decode it in one step, exactly as this tool does, so never treat a Base64 string as a secret.

What is the difference between Base64 and Base64URL?

Base64URL is the URL- and filename-safe variant defined in RFC 4648 §5. It replaces + with - and / with _, and usually drops the = padding so the string can sit in a URL or filename unescaped. This decoder detects and handles both automatically.

Why does my Base64 string end in = or ==?

Padding. Base64 works in 3-byte groups; when the input length isn't divisible by three, one or two = characters are appended to complete the final 4-character block. Missing padding is tolerated here, so partial strings still decode.

Can I decode a Base64 image or file?

Yes — decode it to see the bytes and hex preview. If you have a full data: URI, the Base64 Media Data URI Decoder will also render an image, audio or video preview of the payload.

Yes. Decoding happens entirely in your browser with client-side JavaScript. The string you paste is never uploaded, logged or sent to a server.

Base64 Decoder

Decode standard and URL-safe Base64 to text or raw bytes, instantly and locally.

live · client-sideData, Radix & Stringfree · no sign-up

RAW INPUT

DECODED

Output appears here as you type — decoded on your device.

Input is processed on your device. Nothing you paste is sent anywhere.

What is the Base64 Decoder?

A Base64 decoder converts a Base64-encoded string back into the original bytes it represents, mapping every four Base64 characters back to the three bytes they encode.

Base64 represents binary data using 64 printable ASCII characters (A–Z, a–z, 0–9, plus + and /), so bytes can travel through channels that only carry text: email bodies, JSON fields, data URIs, HTTP headers and JWTs. Every 3 bytes of input becomes 4 characters of output, which is why Base64 inflates data by roughly 33%, and why trailing = characters appear when the input length isn't a multiple of three.

Base64 is an encoding, not encryption. There is no key and no secret — anyone holding the string can reverse it, which is exactly what this decoder does. That is worth remembering whenever you see a config value or a token 'protected' by Base64: it is obfuscation at best.

This decoder accepts both the standard alphabet and the URL-safe variant (RFC 4648 §5, which swaps + and / for - and _), tolerates missing padding, newlines and stray whitespace, and shows the decoded text alongside the byte count and a hex preview so you can tell a readable string from a binary blob at a glance.

Base64 Decoder at a glance

Standard: RFC 4648 (Base64 and Base64URL)
Alphabet: A–Z a–z 0–9 + / with = padding
Size overhead: +33% (4 characters per 3 bytes)
Reversible: Yes — no key involved, it is not encryption

How to use the Base64 Decoder

1Paste your Base64 string into the input panel — padding, line breaks and whitespace are all handled for you.
2Read the decoded text on the right; the byte count and hex preview tell you whether the payload is text or binary.
3Copy the result with one click, or clear the panel and paste the next string.

When you would reach for it

Reading a Base64 chunk out of a JSON payload, config file or environment variable.
Inspecting the Authorization: Basic header that a client sent to your API.
Unpacking a Base64URL segment from a JWT, SAML response or signed cookie.

Base64 Decoder — frequently asked questions

Last reviewed 25 July 2026 · questions or corrections: contact@decoder.tools