Base64 Decoder

What Is It?

The Base64 Decoder converts Base64-encoded strings back into their original plain text or binary representation. Base64 is an encoding scheme used to transport binary data over text-based channels — you’ll find it in JWT tokens, data URIs, email attachments, and API payloads.

This tool decodes instantly in your browser with full privacy. No data is sent to any server.

How to Use

1. Paste your Base64-encoded string into the input field.
2. Click Decode (or decoding triggers automatically).
3. The decoded output appears in the result panel.
4. Use the Copy button to copy the plain text result.

Example

Input (Base64):

SGVsbG8sIFdvcmxkISBUaGlzIGlzIGEgQmFzZTY0IHRlc3Qu

Decoded Output:

Hello, World! This is a Base64 test.

JWT Payload Example (Base64 URL-encoded):

Input: eyJ1c2VySWQiOiIxMjMiLCJyb2xlIjoiYWRtaW4ifQ

Output: {"userId":"123","role":"admin"}

Benefits

• Instant decoding — no round-trip, no latency, result appears immediately.
• Supports standard and URL-safe Base64 — handles both +/ and -_ variants.
• JWT-friendly — perfect for decoding the payload section of JSON Web Tokens.
• Completely private — secrets and tokens stay in your browser, never transmitted.

Common Use Cases

• Decoding the payload of a JWT token to inspect claims (sub, exp, role, etc.).
• Reading data URIs embedded in HTML or CSS (e.g., data:image/png;base64,...).
• Decoding Base64-encoded environment variables or Kubernetes secrets.
• Inspecting Base64 values from API responses or webhook payloads.
• Recovering plain text from encoded email attachments (MIME encoding).

Frequently Asked Questions

What is Base64?

Base64 is a binary-to-text encoding scheme that represents binary data using 64 printable ASCII characters (A-Z, a-z, 0-9, +, /). It’s not encryption — it’s a reversible encoding format.

Is Base64 the same as encryption?

No. Base64 is encoding, not encryption. Anyone with the encoded string can decode it instantly. Never use Base64 to “secure” sensitive data.

Can I decode a full JWT here?

The tool will decode the payload section of a JWT (the middle segment between the two . dots). Note: decoding a JWT reveals its claims but does not verify its signature — use a dedicated JWT verifier for signature validation.

What’s the difference between standard Base64 and URL-safe Base64?

Standard Base64 uses + and / as special characters. URL-safe Base64 replaces them with - and _ to avoid conflicts with URL query parameters. This tool handles both variants automatically.

What happens if the input is invalid Base64?

The tool detects malformed input and displays a clear error message indicating the decoding failed, rather than producing garbled output silently.