Detecting Safari Private Browsing Mode

Cookies gave us personalization; HTML5 added localStorage and sessionStorage. Safari, however, blocks local storage APIs entirely when private browsing is enabled. Calls throw errors, so we may want to detect the mode and inform the user.

Code

function isPrivateMode() {
  let isPrivate = false;
  try {
    window.openDatabase(null, null, null, null);
  } catch (e) {
    isPrivate = true;
  }
  return isPrivate;
}

if (isPrivateMode()) {
  alert('Local storage is unavailable. Please disable private browsing.');
  window.location.href = 'https://support.apple.com/HT203036';
}

Reference

• Apple support article on private browsing: https://support.apple.com/HT203036

Notes

I avoid touching localStorage or sessionStorage directly for detection because Safari 11 changed how those APIs behave. Probing openDatabase still works reliably.