Check a password securely in the Pwned Passwords database. Go to the page and input an SHA-1 to see if it is breached.

• Open a new Incognito window
• Press F12 to open the developer toolbar
• Go to the Network tab
• Check the Offline checkbox
• Go to the Console tab
• Paste this code and press enter: (code from here)

async function sha1(message) {
  const msgBuffer = new TextEncoder('utf-8').encode(message);
  const hashBuffer = await crypto.subtle.digest('SHA-1', msgBuffer);
  const hashArray = Array.from(new Uint8Array(hashBuffer));
  const res = hashArray.map(b => ('00' + b.toString(16)).slice(-2)).join('');
  console.log(res);
}

• Enter sha1("..."), substituting ... with your password, then press enter
• You'll see a bunch of characters and numbers, similar to this: a9993e364706816aba3e25717850c26c9cd0d89d
• This is the password's SHA-1 hash, copy it
• Close the incognito window

• Go to https://sashee.github.io/haveibeenpwned-sha1-query/
• Enter the SHA-1, then click the button
• It will show whether the password is a known breached password