test net address different for same seed

ok so I have tried makeing a javascript html file to do this not sure if it works but seem to

This seems to work, this requires some external imports

https://github.com/jubalix/BTC-Address-Check/blob/main/btc_address_checker.html

This version does not, you should be able to run it offline but is more limited to bc1 addressess

https://github.com/jubalix/BTC-Address-Check/blob/main/btc_address_checker_offline.html

code for first one

Quote

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>BTC Address Equivalence Checker</title>
<style>
  body { font-family: system-ui, sans-serif; max-width: 600px; margin: 2rem auto; }
  input, button { width: 100%; padding: .5rem; margin-top: .5rem; font-size: 1rem; }
  pre { background:#f6f6f6; padding:1rem; border-radius:8px; }
  .ok { color:green; }
  .no { color:red; }
</style>
</head>
<body>
<h2>Bitcoin Mainnet ↔ Testnet Address Checker</h2>

<label>Mainnet or Testnet Address A:</label>
<input id="addrA" placeholder="bc1... or 1... or m...">

<label>Address B:</label>
<input id="addrB" placeholder="tb1... or m... or 1...">

<button id="btn">Compare</button>

<pre id="out"></pre>

<script type="module">
import { bech32 } from 'https://cdn.jsdelivr.net/npm/@scure/[email protected]/+esm';
import bs58check from 'https://cdn.jsdelivr.net/npm/[email protected]/+esm';

function decodeAddress(addr) {
  addr = addr.trim();
  if (addr.toLowerCase().startsWith('bc1') || addr.toLowerCase().startsWith('tb1')) {
   const { prefix, words } = bech32.decode(addr);
   const version = words[0];
   const program = bech32.fromWords(words.slice(1));
   return { type: 'bech32', hrp: prefix, version, payload: bytesToHex(program) };
  } else {
   const buf = bs58check.decode(addr);
   const version = buf[0];
   const payload = buf.slice(1);
   return { type: 'base58', version, payload: bytesToHex(payload) };
  }
}

function bytesToHex(b){return Array.from(b, x=>x.toString(16).padStart(2,'0')).join('');}

function compare(a,b){
  try {
   const A = decodeAddress(a), B = decodeAddress(b);
   const eq = A.payload === B.payload && A.type === B.type;
   return {A,B,equivalent:eq};
  } catch(e){ return {error:e.message}; }
}

document.getElementById('btn').onclick = () => {
  const a = document.getElementById('addrA').value;
  const b = document.getElementById('addrB').value;
  const r = compare(a,b);
  const out = document.getElementById('out');
  if (r.error) { out.innerHTML = `<span class=no>Error:</span> ${r.error}`; return; }
  out.innerHTML = `
A → ${JSON.stringify(r.A, null, 2)}
\nB → ${JSON.stringify(r.B, null, 2)}
\nResult: <strong class="${r.equivalent?'ok':'no'}">
${r.equivalent ? 'Equivalent ✅' : 'Different ❌'}
</strong>`;
};
</script>
</body>
</html>