How to use the Base64 encoder and decoder
Convert plain text to Base64 or turn Base64 back into text. Enter the content, choose the mode and variant, then use the result in the read-only output area.
- Enter plain text or a Base64 string in the input area.
- Choose Auto-detect, Encode, or Decode.
- Choose Standard (+ /) or URL-Safe (- _) from Variant.
- Use the result in the read-only output area, then select Copy or Download.
Encode or decode text
Encode converts the entered text to Base64 using UTF-8 bytes. Decode converts Base64 bytes back to UTF-8 text. For encoding, Standard (+ /) keeps the standard symbols. URL-Safe (- _) replaces them and removes trailing padding.
For decoding, the tool accepts both symbol sets, regardless of the selected Variant.
Upload or drop text content
Select Upload or use the visible Drop file area to load content into the input. The page reads files as text, so it does not preserve arbitrary binary bytes. Decoding also produces text rather than reconstructing a binary file.
Auto-detect limitations
Auto-detect is a heuristic, not a validation step. The tool trims the input and removes whitespace before testing it. It selects Decode only for non-empty input made from accepted Base64 characters whose cleaned length is divisible by 4. Otherwise, it treats the input as text to encode.
Select explicit Encode or Decode when you already know the direction, especially for unpadded Base64 input.
Troubleshoot decoding errors
If explicit Decode receives invalid input, the tool clears the output and shows an error in the status area. Check for characters outside the accepted alphabet and try again. Explicit Decode adds missing padding before decoding. Malformed UTF-8 bytes may appear as replacement characters in the returned text.
Privacy and processing limitations
The conversion code processes entered content in the browser and does not send the tool input to a server. The page also loads external analytics scripts, so avoid treating the page as completely private. This interface processes text; it is not a binary file converter.
Frequently asked questions
Why did my decoded output come out empty or garbled?
This usually means the input is not valid Base64 or the decoded bytes are not valid UTF-8 text. Check for characters outside the accepted alphabet and check the status message for details.
Do I need to add padding manually?
Explicit Decode adds missing = padding before decoding. Auto-detect may not recognize unpadded input because it selects Decode only when the cleaned length is divisible by 4.
Is this tool private?
The conversion code runs in your browser and does not send the tool input to a server. The page loads external analytics scripts, so this is not an absolute privacy guarantee.
Which Base64 variant should I choose?
Choose Standard (+ /) for standard Base64 output or URL-Safe (- _) when the receiving format expects those substitutions. Encoding uses the selected variant; decoding accepts both symbol sets.
What do Copy and Download do?
Copy writes the current output to the clipboard. Download saves the output as a text file named from the page path with an -output.txt suffix.