What Is Base64 Decoding?
Base64 decoding is the reverse process of Base64 encoding. It takes a Base64-encoded ASCII string and converts it back into the original text data. If you have received data that has been encoded using Base64, this tool will help you recover the original content instantly.
Base64-encoded strings are easy to recognize: they consist only of the characters A-Z, a-z, 0-9, +, /, and may end with one or two = padding characters.
Tip: A valid Base64 string always has a length that is a multiple of 4. If your encoded string has a different length, it may be missing padding characters (=) or may be using the Base64URL variant.
When Do You Need to Decode Base64?
- Reading email source — Email messages often contain Base64-encoded attachments and body content.
- Debugging APIs — API responses, authentication tokens (like JWTs), and request headers often contain Base64-encoded data.
- Analyzing web content — Data URIs in HTML/CSS embed Base64-encoded images and fonts.
- Reading configuration files — Many configuration systems store values in Base64 encoding.
- Inspecting certificates — SSL/TLS certificates in PEM format use Base64 encoding.
Common Base64 Decoding Errors
- Invalid characters — The input contains characters outside the Base64 alphabet.
- Incorrect padding — Missing required = padding characters at the end.
- Truncated input — The encoded string was cut off during copying.
- Wrong variant — The data may use Base64URL encoding (with - and _ instead of + and /).
Frequently Asked Questions
Is Base64 decoding the same as decryption?
No. Base64 is an encoding scheme, not encryption. Decoding Base64 simply reverses the encoding process — it does not require any key.
Why does my decoded text look like gibberish?
This usually means the original data was binary content (not text), or the text was encoded using a different character encoding than UTF-8.