Apache Commons Codec is a mature Java library providing a comprehensive set of encoders and decoders for binary-to-text formats (Base16, Base32, Base64, Base45, Base58, Hex), digest and hash algorithms (MD5, SHA-1/2/3, MurmurHash, XXHash32, Blake3, CRC16/32), phonetic encoding (Soundex, Metaphone, Caverphone, Beider-Morse, Daitch-Mokotoff), and network codecs (URL encoding, Quoted-Printable, RFC 1522 MIME). The architecture is modular with clear package separation: `binary`, `digest`, `language`, `net`, and `cli`. Key design patterns include a builder pattern for configuring codecs (e.g., `Base64.builder()`), an abstract base class `BaseNCodec` with streaming support via `BaseNCodecInputStream`/`OutputStream`, and a `CodecPolicy` enum for strict vs. lenient decoding. The library has no production dependencies; only test dependencies on commons-lang3 and commons-io. It is widely used across the Java ecosystem, with extensive test coverage including RFC vectors and backward compatibility tests. However, some deprecated methods and known bugs (e.g., in MurmurHash3 legacy methods) are preserved for compatibility, and certain algorithms (SHAKE) require Java 25, introducing version drift.