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Base64 Decoder

Decode Base64 encoded text back to readable format

About the Base64 Decoder

This tool Base64 decodes a string back into readable text, handling both standard and URL-safe variants. It is the quick way to read a JWT payload, an encoded config value or the contents of a data URI.

Base64 decode a string whenever you find one and need to know what it says. JWT payloads, encoded environment variables, email headers, data URIs and Kubernetes secrets are all Base64, and all readable in a second once decoded.

Both variants are accepted. Standard Base64 uses plus and slash characters, while the URL-safe variant substitutes minus and underscore so the string can sit in a URL or filename — JWTs use the URL-safe form, which is why a naive decoder sometimes fails on them.

Worth remembering what this implies about security: because Base64 is trivially reversible, anything merely Base64-encoded is effectively in plain sight. A Kubernetes secret stored as Base64 is obscured, not protected.

How to use the Base64 Decoder

  1. Paste the Base64 string. Enter the encoded text. Standard and URL-safe variants both work.
  2. Decode. The readable text appears immediately.
  3. Check for padding issues. If decoding fails, the string may be truncated or missing padding.
  4. Copy the result. Take the decoded text.

Base64 Decoder features

  • Decodes standard and URL-safe Base64
  • Handles UTF-8 text including accents and emoji
  • Works on JWT payload segments
  • Instant decoding as you type
  • Clear reporting when a string is not valid Base64
  • Runs entirely in your browser

Frequently asked questions

What can I decode with this?

Any Base64 string — JWT payloads, encoded environment variables, email headers, data URIs and Kubernetes secrets.

Does it handle URL-safe Base64?

Yes. Both the standard plus-and-slash form and the URL-safe minus-and-underscore form used by JWTs are accepted.

Why does my string fail to decode?

Usually it is truncated or missing padding. Base64 length must be a multiple of four, padded with equals signs.

Is Base64 a form of encryption?

No. It is trivially reversible, so anything only Base64-encoded is effectively readable by anyone who finds it.

Is my string sent to a server?

No. Decoding happens in your browser, so tokens and secrets stay on your machine.