{
  "id": "encoding/base32",
  "family": "encoding",
  "slug": "base32",
  "title": "Base32 (RFC 4648 §6)",
  "summary": "Base32 maps every 5 input bytes (40 bits) to 8 ASCII characters drawn from a 32-symbol alphabet (A–Z and 2–7), padding the final group with '=' to a multiple of 8 characters. It trades density for a case-insensitive, human-transcribable alphabet that omits the easily confused 0/1/8/9, which is why it backs TOTP/HOTP secrets (RFC 4226/6238) and onion addresses.",
  "kind": "encoding",
  "aliases": [
    "base-32",
    "RFC 4648 base32"
  ],
  "status": "standard",
  "verification": "verified",
  "tier": "A",
  "source_url": "https://www.rfc-editor.org/rfc/rfc4648#section-6",
  "source_version": "RFC 4648 §6",
  "retrieved_date": "2026-05-29",
  "see_also": [
    "encoding/base64",
    "encoding/base16"
  ],
  "ext_type": "encoding@1",
  "ext": {
    "rfc": "RFC4648",
    "charset": "US-ASCII",
    "algorithm": "base32",
    "alphabet": "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567",
    "notes": [
      "Encodes 40 input bits (5 bytes) as eight 5-bit groups; each group indexes the 32-character alphabet. Output length is always a multiple of 8.",
      "Padding map (bytes in last group -> '=' count): 1 byte -> 6 pads ('======'); 2 -> 4 ('===='); 3 -> 3 ('==='); 4 -> 1 ('='); 5 -> 0. So 'f' (1 byte) -> 'MY======'.",
      "The alphabet deliberately omits 0, 1, 8, 9 to avoid confusion with O, I/L, B; decoders are case-insensitive in practice though RFC 4648 specifies the uppercase canonical form.",
      "RFC 4648 §7 also defines 'base32hex' (alphabet 0–9 A–V), a different, order-preserving variant — not covered by this entry."
    ],
    "test_vectors": [
      {
        "input": "",
        "input_form": "utf8",
        "output": "",
        "output_form": "ascii",
        "algorithm": "base32",
        "direction": "encode",
        "note": "RFC 4648 §10 test vector: BASE32(\"\") = \"\"."
      },
      {
        "input": "f",
        "input_form": "utf8",
        "output": "MY======",
        "output_form": "ascii",
        "algorithm": "base32",
        "direction": "encode",
        "note": "RFC 4648 §10 test vector: BASE32(\"f\") = \"MY======\"."
      },
      {
        "input": "fo",
        "input_form": "utf8",
        "output": "MZXQ====",
        "output_form": "ascii",
        "algorithm": "base32",
        "direction": "encode",
        "note": "RFC 4648 §10 test vector: BASE32(\"fo\") = \"MZXQ====\"."
      },
      {
        "input": "foo",
        "input_form": "utf8",
        "output": "MZXW6===",
        "output_form": "ascii",
        "algorithm": "base32",
        "direction": "encode",
        "note": "RFC 4648 §10 test vector: BASE32(\"foo\") = \"MZXW6===\"."
      },
      {
        "input": "foob",
        "input_form": "utf8",
        "output": "MZXW6YQ=",
        "output_form": "ascii",
        "algorithm": "base32",
        "direction": "encode",
        "note": "RFC 4648 §10 test vector: BASE32(\"foob\") = \"MZXW6YQ=\"."
      },
      {
        "input": "fooba",
        "input_form": "utf8",
        "output": "MZXW6YTB",
        "output_form": "ascii",
        "algorithm": "base32",
        "direction": "encode",
        "note": "RFC 4648 §10 test vector: BASE32(\"fooba\") = \"MZXW6YTB\" (5 bytes -> 8 chars, no padding)."
      },
      {
        "input": "foobar",
        "input_form": "utf8",
        "output": "MZXW6YTBOI======",
        "output_form": "ascii",
        "algorithm": "base32",
        "direction": "encode",
        "note": "RFC 4648 §10 test vector: BASE32(\"foobar\") = \"MZXW6YTBOI======\"."
      },
      {
        "input": "MZXW6YTBOI======",
        "input_form": "ascii",
        "output": "foobar",
        "output_form": "utf8",
        "algorithm": "base32",
        "direction": "decode",
        "note": "Round-trip: BASE32-decode(\"MZXW6YTBOI======\") = \"foobar\"."
      }
    ]
  },
  "updated": "2026-05-29T00:00:00Z"
}