Base64 Decoder
Decode Base64 back to readable text with strict validation and clear error messages.
Runs in your browser, your data never leaves your deviceFree, no sign-up
Decoded text
The decoded text will appear here.
How it works
The input is validated strictly before anything is decoded: only the standard Base64 alphabet, optional padding at the end, and a length that is a multiple of 4 are accepted. That way corrupted input produces a clear error message instead of garbage output.
The decoded bytes are then interpreted as UTF-8 text, so Unicode content comes back exactly as it was originally encoded.
Features
- Strict validation with specific, actionable errors
- Unicode-safe output (UTF-8 bytes)
- Line breaks and whitespace in input are ignored
- Copy, download and upload actions
- 100% client-side, nothing leaves your browser
How to use
- Paste the Base64 string (line breaks are fine).
- Press Decode Base64.
- Copy or download the decoded text.
Example
Input: SGVsbG8sIFdvcmxkIQ==
Output: Hello, World!Frequently asked questions
- Why does my Base64 fail to decode?
- The most common causes are: characters outside the Base64 alphabet (such as - or _ from the URL-safe variant), a length that is not a multiple of 4 (truncated copy/paste), or more than two padding = characters. This tool checks all of these and tells you which one it found.
- Can it decode Base64 containing emoji or accented characters?
- Yes. The decoded bytes are interpreted as UTF-8, so text that was encoded from Unicode decodes back exactly as it was, including emoji, accented letters and non-Latin scripts.
- Does it support URL-safe Base64 (- and _)?
- Not directly, because this tool uses the standard alphabet (+ and /). If your input uses the URL-safe variant, replace - with + and _ with / before decoding, and add padding = characters until the length is a multiple of 4.
- Is my data sent to a server?
- No. Decoding happens entirely in your browser with JavaScript. Nothing you paste is transmitted anywhere, and you can verify this in your browser's network inspector.
- Can I decode Base64 that contains line breaks?
- Yes. Whitespace between groups (including line wraps, which some encoders insert every 76 characters) is ignored before decoding, as allowed by RFC 4648.