Base64 decoder
This Base64 decoder reverses Base64 encoding and shows the original text or the raw bytes. It helps developers read encoded values found in API responses, email sources, config files and tokens.
- Runs in your browser
- Free, no account needed
- Copy or download the result
Result
Example
SGVsbG8sIHdvcmxkIQ==
Hello, world!
How to use the base64 decoder
- Paste the encoded value into the Base64 to decode box.
- Choose the Alphabet (Standard Base64 or Base64url) and the Whitespace setting.
- Set Decoded output to UTF-8 text or Hexadecimal bytes.
- Press Run, then Copy result or Download.
How it works
Missing = padding is accepted, but padding that is present must be the correct amount.
Characters outside the chosen alphabet are rejected. Standard Base64 expects + and /, while Base64url expects - and _.
Spaces and line breaks cause an error unless you choose Allow spaces and line breaks.
Input with an impossible length, or with leftover bits that a correct encoder would set to zero, is rejected as not canonical.
If the bytes are not valid UTF-8 text, the tool says so. Switch to Hexadecimal bytes to see them, for example when the data is an image or other binary file.
Everything runs in your browser. Your input is not uploaded or stored.
Questions and answers
Why do I get an error that the bytes are not valid UTF-8?
The decoded data is probably binary, such as an image or compressed file, or text in another encoding. Set Decoded output to Hexadecimal bytes to inspect the bytes instead.
Can it decode Base64 without padding?
Yes. Input without trailing = signs is accepted. If padding is included, it must match the length of the data.
Why does it reject line breaks?
The default is strict so stray characters get noticed. Choose Allow spaces and line breaks for Base64 that was wrapped across several lines.
Is my data sent to a server?
No. Decoding runs in your browser and nothing is uploaded.