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GHC 9.10.3 · lts/ghc-9.10.x · c74966e · 2026-09-27

Modulebase64-1.0Haskell2010

Data.ByteString.Short.Base64.URL

This module contains ShortByteString-valued combinators for implementing the RFC 4648 specification of the Base64url encoding format. This includes strictly padded/unpadded and lenient decoding variants, as well as internal and external validation for canonicity.

  • 13 values
  • Packagebase64-1.0
  • Exports13
  • LanguageHaskell2010
  • LicenceBSD-3-Clause
  • SourceURL.hs

Encoding

4 declarations

Decoding

7 declarations

Decode a Base64url encoded ShortByteString value, either padded or unpadded. The correct decoding function is dispatched based on the existence of padding.

For typed values: - If a padded value is required, use decodeBase64Padded - If an unpadded value is required, use decodeBase64Unpadded

See: RFC-4648 section 4

Examples:
Example1 expression
decodeBase64 $ assertBase64 @'UrlPadded "PDw_Pj4=""<<?>>"
Example1 expression
decodeBase64 $ assertBase64 @'UrlUnpadded "PDw_Pj4""<<?>>"

Decode an untyped Base64url encoded ByteString value. If its length is not a multiple of 4, then padding chars will be added to fill out the input to a multiple of 4 for safe decoding as Base64url-encoded values are optionally padded.

For a decoder that fails to decode untyped values of incorrect size: - If a padded value is required, use decodeBase64PaddedUntyped - If an unpadded value is required, use decodeBase64UnpaddedUntyped

See: RFC-4648 section 4

Examples:
Example1 expression
decodeBase64Untyped "PDw_Pj4="Right "<<?>>"
Example1 expression
decodeBase64Untyped "PDw_Pj4"Right "<<?>>"
Example1 expression
decodeBase64Untyped "PDw-Pg="Left "Base64-encoded bytestring has invalid padding"
Example1 expression
decodeBase64Untyped "PDw-Pg"Right "<<>>"

Decode an unpadded, untyped Base64url encoded ByteString value. If its length is not a multiple of 4, then padding chars will be added to fill out the input to a multiple of 4 for safe decoding as Base64url-encoded values are optionally padded.

In general, unless unpadded Base64url is explicitly required, it is safer to call decodeBase64.

See: RFC-4648 section 4

Examples:
Example1 expression
decodeBase64UnpaddedUntyped "PDw_Pj4"Right "<<?>>"
Example1 expression
decodeBase64UnpaddedUntyped "PDw-Pg="Left "Base64-encoded bytestring has invalid padding"
Example1 expression
decodeBase64UnpaddedUntyped "PDw-Pg"Right "<<>>"

Leniently decode an unpadded, untyped Base64url-encoded ShortByteString. This function will not generate parse errors. If input data contains padding chars, then the input will be parsed up until the first pad character.

Note: This is not RFC 4648-compliant.

Examples:
Example1 expression
decodeBase64Lenient "PDw_Pj4=""<<?>>"
Example1 expression
decodeBase64Lenient "PDw_%%%$}Pj4""<<?>>"

Validation

2 declarations

Tell whether an untyped ShortByteString is Base64url-encoded.

Examples:
Example1 expression
isBase64Url "PDw_Pj4="True
Example1 expression
isBase64Url "PDw_Pj4"True
Example1 expression
isBase64Url "PDw_Pj"False

Tell whether an untyped ShortByteString is a valid Base64url format.

This will not tell you whether or not this is a correct Base64url representation, only that it conforms to the correct shape. To check whether it is a true Base64 encoded ShortByteString value, use isBase64Url.

Examples:
Example1 expression
isValidBase64Url "PDw_Pj4="True
Example1 expression
isValidBase64Url "PDw_Pj"True
Example1 expression
isValidBase64Url "%"False