Segwit address decode

segwit-address-decode · version 1.0.0 · Encoding & checksums · free, no key needed

Decode a native segwit address into witness version, program hex, and script pubkey.

Use when you need to: decode native segwit address · segwit address to witness program · parse bech32 witness address.

Decide before calling

Read the versioned contract and the supported scope below. Reuse segwit-address-decode@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use segwit-address-decode@1.0.0 for decode native segwit address. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• decode native segwit address
• segwit address to witness program
• parse bech32 witness address
• parse bech32m witness address
• read witness version from segwit address
• segwit address to script pubkey
• decode uppercase segwit address

Not supported

• encode a witness program into an address
• return a valid or invalid verdict without the program
• hash or verify a key inside the program
• locate a typo in the checksum

Behavior

• expected_hrp must already be lowercase US-ASCII (code points 33..126 excluding 65..90). An uppercase expected_hrp such as BC is invalid_input with details.reason invalid_hrp and is not case-folded.
• The address may be all-lowercase or all-uppercase. Mixed case is rejected. The decoded HRP is the lowercased address HRP and must equal expected_hrp exactly; a different HRP is invalid_input with details.reason hrp_mismatch.
• Version 0 must use a valid Bech32 checksum and a 20-byte or 32-byte program. Versions 1 through 16 must use a valid Bech32m checksum and a program of 2 to 40 bytes. The other checksum constant is details.reason wrong_encoding, not a second acceptance.
• Failure order after the lowercase expected_hrp check: character range, mixed case, separator, checksum, empty data, padding, program length, witness version, version-0 length, checksum variant, then HRP equality.
• Address length above 90 characters, or expected_hrp length above 83 characters, is limit_exceeded before checksum work. The address limit is checked before the expected_hrp limit.
• The program bytes are returned as given. They are not checked as a hash or a key. script_pubkey_hex is the BIP 141 witness script (OP_n plus a single-byte push).
• Disclaimer: format transform only; provides no confidentiality, integrity, or authenticity.

Input

• address (string, required): min length 1; max length 90
• expected_hrp (string, required): min length 1; max length 83; pattern ^[\x21-\x40\x5b-\x7e]+$

Output

• normalized_address (string, required): min length 13; max length 90; pattern ^[\x21-\x40\x5b-\x7e]{1,83}1[qpzry9x8gf2tvdw0s3jn54khce6mua7l]+$
• hrp (string, required): min length 1; max length 83; pattern ^[\x21-\x40\x5b-\x7e]+$
• witness_version (integer, required): min 0; max 16
• program_hex (string, required): min length 4; max length 80; pattern ^(?:[0-9a-f]{2}){2,40}$
• encoding (one of "bech32", "bech32m", required)
• script_pubkey_hex (string, required): min length 8; max length 84; pattern ^(?:[0-9a-f]{2}){4,42}$

Limits

• max address chars: 90
• max hrp chars: 83

Example

Request input:

{
  "address": "BC1QW508D6QEJXTDG4Y5R3ZARVARY0C5XW7KV8F3T4",
  "expected_hrp": "bc"
}

Response:

{
  "result": {
    "normalized_address": "bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4",
    "hrp": "bc",
    "witness_version": 0,
    "program_hex": "751e76e8199196d454941c45d1b3a323f1433bd6",
    "encoding": "bech32",
    "script_pubkey_hex": "0014751e76e8199196d454941c45d1b3a323f1433bd6"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "segwit-address-decode",
  "version": "1.0.0",
  "input": {
    "address": "BC1QW508D6QEJXTDG4Y5R3ZARVARY0C5XW7KV8F3T4",
    "expected_hrp": "bc"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/segwit-address-decode/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"address":"BC1QW508D6QEJXTDG4Y5R3ZARVARY0C5XW7KV8F3T4","expected_hrp":"bc"}'

The machine-readable contract is at /v1/tools/segwit-address-decode/versions/1.0.0.

CLI

node cli.mjs run segwit-address-decode 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Segwit address encode: Encode a witness program as a native segwit address using Bech32 for v0 and Bech32m for v1-v16.
• Bech32 decode: Decode Bech32 or Bech32m text into a lowercase HRP, 5-bit data, and the checksum variant.
• Segwit address validate: Validate a native segwit address and report which Bech32 or Bech32m rule failed.
• Pem envelope parse: Parse one RFC 7468 textual envelope into its label and lowercase hex bytes.
• Bech32 encode: Encode lowercase HRP and 5-bit data as Bech32 or Bech32m text using that checksum.
• Cid parse: Parse a CIDv0 or CIDv1 envelope without hashing content.