Base64 Decoder
Decode Base64 strings back into readable text instantly.
How it works
If you've received or found a Base64-encoded string -- from an API response, a config file, a JWT segment, or an email attachment header -- this tool converts it straight back to readable text. Base64 decoding reverses the encoding process exactly: every 4 characters of Base64 map back to 3 bytes of original data.
This decoder handles UTF-8 multi-byte characters correctly, so if the original text included accented characters, emoji, or non-Latin scripts, they come back intact rather than as garbled symbols -- a common failure mode in simpler decoders that only handle plain ASCII.
Decoding runs entirely in your browser via the standard atob() API; your input never leaves your device.
Frequently asked questions
What happens if the Base64 is invalid?
You'll see a clear error message instead of garbled output, so you know immediately the input wasn't valid Base64 rather than getting confusing partial results.
Why do I get strange characters after decoding?
This usually means the original data wasn't UTF-8 text (it might be binary data like an image), or the Base64 string was truncated/corrupted before you pasted it.
Can I decode a JWT with this?
You can decode individual segments of a JWT (which are Base64URL, a close variant), but for full JWT decoding including header and payload together, use the dedicated JWT Decoder tool instead.
Does whitespace in the input cause errors?
No -- the decoder trims surrounding whitespace automatically before decoding.