Encoding

Base64 Decode

Decode Base64 — or URL-safe base64url — back to readable UTF-8 text as you type. Tolerant of missing padding and line breaks, so it works on copy-pasted tokens, JWT segments, and config blobs.

Published February 20, 2024
Last reviewed June 28, 2026

Tool Summary Answer Block

This tool accepts structured input and returns deterministic output in the browser with no server upload.

Tool name: Base64 Decode
Input intent: Provide source content to transform, validate, or analyze.
Output intent: Receive normalized output suitable for copy, reuse, or debugging.
Example input: SGVsbG8sIHdvcmxk
Example output: Hello, world

0Base64 chars0decoded chars0bytes

Base64 inputDrop file

Plain text outputRead-only

Need to encode instead? Switch to Base64 Encode

Tool Introduction

Decode Base64 — or URL-safe base64url — back to readable UTF-8 text as you type. Tolerant of missing padding and line breaks, so it works on copy-pasted tokens, JWT segments, and config blobs.

Tool Overview

Base64 is a way to represent arbitrary bytes using 64 printable ASCII characters so they survive transport through URLs, JSON, headers, and email. Decoding reverses that: it reads the Base64 characters, regroups them into bytes, and interprets those bytes as UTF-8 text. This decoder is forgiving — it strips whitespace and line breaks, accepts both the standard (+, /) and URL-safe (-, _) alphabets, and restores any missing = padding automatically, so a token pasted from a log or a JWT decodes cleanly. If the input is not valid Base64 it tells you instead of returning garbage. Decoding happens entirely in your browser, so even sensitive strings stay on your device. Keep in mind Base64 is encoding, not encryption — decoding it requires no key.

Use Cases

Read the header or payload of a JWT without running any code
Inspect a Base64 value pulled from a log line, config file, or API response
Recover the original text from a data: URL or HTTP Basic Authorization header
Verify that something you Base64-encoded round-trips back correctly
Decode a base64url token from a query string or password-reset link

Input/Output Examples

Standard Base64 decodes straight back to text.

Input Intent

SGVsbG8sIHdvcmxk

Output Intent

Hello, world

UTF-8 bytes are decoded, so accents and emoji come back intact.

Input Intent

Y2Fmw6kg8J+Riw==

Output Intent

café 👋

URL-safe base64url (note the _ and missing padding) decodes too.

Input Intent

c3ViamVjdHM_dmFsdWU9YS9iK2M

Output Intent

subjects?value=a/b+c

FAQ

Why does my input show as invalid?+

The string contains characters that are not part of the Base64 alphabet, or its length is wrong. Make sure you copied the whole value and did not include surrounding quotes or stray characters.

Do I need to add the = padding myself?+

No. If the padding is missing — common with JWTs and base64url tokens — the decoder restores it automatically before decoding.

Does it support URL-safe base64url?+

Yes. It accepts both the standard alphabet (+, /) and the URL-safe one (-, _), so JWT segments and query-string tokens decode without any conversion.

Can I decode a whole JWT here?+

You can decode each dot-separated segment individually to see the header and payload. For a full, structured view with expiry and claims, use the dedicated JWT Decoder.

Is my data sent to a server?+

No. Decoding happens entirely in your browser, so the Base64 string and the decoded result never leave your device.