From Base64

Decodes a Base64 string to raw binary data. Use it when a previous step or API returns Base64 and you need the original bytes for file handling, further decoding, or another transform. Supports the same alphabet presets as To Base64, optional stripping of non-alphabet characters, and strict validation. From Base64 lives in the Data format category of the fx menu.

Alphabet rules follow RFC 4648 (and related variants) when you pick a matching preset.

Parameters

Parameter	Type	Required	Default	Description
Input	string	yes	—	Base64 text to decode.
Alphabet	string	yes	Standard (RFC 4648): A-Za-z0-9+/=	Same alphabet used when the data was encoded. Presets include RFC 4648 standard and URL-safe, plus other common variants.
Remove non-alphabet chars	boolean	yes	true	When on, removes every character that is not in the chosen alphabet before decoding (for example spaces, newlines, or other separators in the Base64 text).
Strict mode	boolean	yes	false	When on, rejects invalid input: length cannot be 4n+1, padding (when the alphabet has a padding symbol) must appear only at the end in the correct form, and no non-alphabet characters may remain after optional stripping.

Input is the primary Base64 string. Alphabet, Remove non-alphabet chars, and Strict mode are controls on the function card.

Returned value

Type	Description
binary	The decoded raw bytes for the Base64 input.

Limitations

• Input must be a string. Non-string input raises fromBase64: functionInput must be a string.
• Alphabet must match the encoder. A URL-safe payload decoded with the standard alphabet (or the reverse) fails or produces wrong bytes.
• With Strict mode on, malformed length, bad padding, or leftover non-alphabet characters raise an error.
• With Remove non-alphabet chars off and separators in the text, decoding fails unless you clean the string first.

Caution

Invalid Base64 for the chosen Alphabet and Strict mode stops evaluation with an error — fix the string or options before re-running the step.

Examples

Decode a standard Base64 string

Decode the most common Base64 form back to bytes. Leave stripping on so whitespace in the string does not block decoding.

1. Set Input to the Base64 string. Paste:

   Input

   aGVsbG8=

2. Leave Alphabet on Standard (RFC 4648): A-Za-z0-9+/=.

3. Leave Remove non-alphabet chars on and Strict mode off.

4. Confirm Output value is the decoded binary (for example the bytes for hello).

Decode with strict validation

Turn Strict mode on when you need to reject malformed Base64 instead of silently accepting odd lengths or padding.

1. Set Input to the Base64 string from the previous step.
2. Match Alphabet to the encoder.
3. Turn Strict mode on.
4. Confirm a well-formed string decodes to binary, or fix the Input if evaluation errors.