About the Base64 Decoder
Paste any Base64 string and this tool decodes it back to its original text, automatically handling both the standard and URL-safe alphabets. Decoding is Unicode-aware, so multi-byte characters produced by the matching encoder come back correctly.
How to use it
- 01Paste the Base64 string you want to decode.
- 02Whitespace and line breaks inside the input are ignored automatically.
- 03Read or copy the decoded text.
- 04If the input is invalid, a plain-language error explains why.
Features
- Accepts both standard and URL-safe (-, _) Base64 alphabets
- Tolerant of missing padding and embedded whitespace
- Unicode-safe decoding via TextDecoder
- Clear, human-readable error messages instead of stack traces
Practical examples
Reading JWT segments
Decode the header or payload segment of a JSON Web Token to inspect its claims.
Debugging API responses
Turn a Base64-encoded field from an API response back into readable text.
Limitations
- Decoded bytes are shown as text; arbitrary binary output (like images) isn't rendered.
- Malformed Base64 with truly corrupted characters cannot be recovered.
Privacy
Decoding runs entirely in your browser; the input never leaves your device.
Read the full privacy policy for how the site as a whole handles data.
Frequently asked questions
Does it matter if my Base64 uses - and _ instead of + and /?
No, both alphabets are normalized automatically before decoding.
What if I get an error?
Check for missing characters, extra symbols, or text that isn't actually Base64 — the tool reports invalid length or characters plainly.
Can it decode binary files like images?
It decodes to text using UTF-8, so binary formats that aren't valid UTF-8 will show garbled characters rather than a usable file.