How to use
- Paste the encoded value, open a file, or try the sample.
- Choose the format. The result updates as you type.
- Copy the result or download the converted data.
Decoding Base64 correctly
Decode Base64 into its original bytes. Valid UTF-8 is shown as text; other binary data gets a hex preview and a byte-preserving download.
Select the matching alphabet and decide whether to accept ASCII whitespace and omitted padding. Invalid characters and inconsistent padding are reported.
Recover the original bytes
Each group of Base64 characters becomes bytes. Text decoding uses strict UTF-8 and preserves a leading BOM. Non-text bytes remain downloadable without being replaced with placeholder characters.
SGVsbG8sIHdvcmxkISDwn5GLHello, world! 👋The default settings convert this input in one pass.
Padding and whitespace
ASCII spaces, tabs, CR and LF can be ignored explicitly. Missing padding can be accepted, but extra padding, misplaced =, mixed alphabets and nonzero unused bits are rejected. The selected alphabet must match the input.
Binary results and plain Base64
The input must be the Base64 value itself. Remove a data URL header before decoding. Binary output is shown only as a limited hex preview; Download exports the complete decoded bytes.
Up to 5 MiB of input, 20 MiB of output, and 10 seconds per run. Text files must use UTF-8. Base64 encoding also accepts binary files. Documents stay on your device.
Frequently asked questions
Why do I see a hex preview?
The decoded bytes are not readable UTF-8. Download saves those bytes unchanged.
Can I decode an unpadded value?
Yes, with Allow missing padding enabled. A one-character remainder is always invalid.
Can I paste wrapped Base64?
Yes, if Ignore ASCII whitespace is enabled. Other unexpected characters remain errors.
Does the decoder accept a data URL?
Paste the Base64 value after the comma, without its data URL header.
Will decoding run a file?
No. The result is text or a download. It is never executed or rendered as a document.