# Base64 Decoder

> Decode Base64 back into readable text, with clear errors for malformed input.

URL: https://uttir.com/base64-decoder
Categories: developer-tools, encoding-tools
Privacy: Decoding happens locally in your browser. Your data is never uploaded.

## About

Paste any standard Base64 string and get the original text back, including Unicode content encoded as UTF-8. Invalid characters or broken padding are reported with a clear explanation instead of a silent failure.

Like the rest of Uttir, decoding runs entirely in your browser — handy for inspecting tokens, data URLs, and encoded payloads that you would rather not paste into a random website.

## How to use

1. **Paste Base64** — Whitespace-free standard Base64 with optional = padding.
2. **Read or copy the result** — The decoded text appears live on the right.

## Examples

### Round trip

Decoding the encoder’s example returns the original text.

Input:

```
aGVsbG8gd29ybGQ=
```

Output:

```
hello world
```

## FAQ

### Why do I get an error about padding?

Standard Base64 length must be a multiple of four characters, padded with "=" if needed. A truncated or hand-edited string usually fails this check.

### Can it decode URL-safe Base64?

This tool expects the standard alphabet. URL-safe variants use "-" and "_" instead of "+" and "/"; replace those two characters before decoding.

### What if the input is not valid Base64?

The tool reports the position of the first invalid character. Fix that, then re-decode. Common issues are missing padding (=) at the end and characters outside the Base64 alphabet.

### What happens if the input is not valid Base64?

The tool reports the position of the first invalid character so you can fix the input. We never send the input to a server, so the decode attempt happens entirely in your browser.

## Related tools

- [Base64 Encoder](https://uttir.com/base64-encoder) — Encode any text — including emoji and non-Latin scripts — into standard Base64.
- [JWT Decoder](https://uttir.com/jwt-decoder) — Decode a JWT’s header and payload and check its expiration — without sending it anywhere.

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For the full HTML page with the live tool, visit https://uttir.com/base64-decoder.
This file is the markdown rendering at https://uttir.com/base64-decoder.md. See https://uttir.com/llms.txt for a site-wide summary.