Paste a Base64-encoded string into the left panel and click Decode to convert it back to plain text. The decoder handles standard Base64 (RFC 4648) and correctly reconstructs UTF-8 multi-byte characters including Unicode, emoji, and CJK text. If the input is not valid Base64, the decoder will show an error. Use Swap to re-encode the decoded output.
How to Base64 decode a string online
- Paste the Base64-encoded string into the left panel.
- Click the Decode button.
- Read the decoded plain text in the right panel.
- Use Swap to encode the decoded text back to Base64.
FAQ
What is Base64 decoding?
Base64 decoding reverses the Base64 encoding process, converting an ASCII string of Base64 characters back to the original binary data or text. Common use cases include reading JWT payload data, decoding HTTP Basic Auth credentials, and extracting data URIs.
What does a Base64 string look like?
Base64 strings consist of letters (A–Z, a–z), digits (0–9), and the characters + and /. They often end with one or two = padding characters. For example, "SGVsbG8=" decodes to "Hello".
What is the difference between Base64 and Base64url?
Base64url replaces + with - and / with _ to make the string safe for use in URLs and file names without percent-encoding. JWTs use Base64url. This decoder handles standard Base64; for JWT payloads, use the JWT Decoder tool.
What happens if the Base64 string is invalid?
If the input contains characters not in the Base64 alphabet, or if the padding is wrong, the decoder will show an error message. Fix the input and try again.
Is my data uploaded anywhere?
No. All decoding happens in your browser. Your data never leaves your device.