Type Method

decode(_:)

Decodes a URL-safe unpadded Base64 string to raw bytes.

static func decode(_ string: String) -> Data?

Parameters

string: The Base64URL-encoded text. Padding is optional in the input; both padded and unpadded forms decode successfully.

Return Value

The decoded Data, or nil if the input contains characters outside the URL-safe alphabet or cannot be aligned to a four-character group with added padding.

Mentioned In

Discussion

Reverses the transformation performed by encode(_:): restores -→+, _→/, re-appends the = padding that RFC 4648 §5 permits to be omitted, and delegates the final decode to Foundation’s Data(base64Encoded:). Invalid input — characters outside the alphabet, or a length that cannot be padded to a multiple of four — returns nil rather than throwing.

Typical consumers: JWT / JWS segments (RFC 7515), Nostr NIP-19 note / nevent payloads, WebAuthn credential blobs, and DID document fields.

Note

This function is a pure Swift wrapper; no libcrypto interaction occurs. Security-sensitive callers should prefer authenticated transports (JWS, signed envelopes) over hand- rolled Base64URL round-tripping.