Posted over 6 years ago. Visible to the public.

How to disable auto-complete on login forms

Disabling auto-complete in login forms is probably a bad idea, since it encourages weak passwords.

If you are still forced to implement this (maybe due to legal or policy requirements), this is how:

Prevent browsers from saving the password in the first place. Disabling autocomplete does not improve security.

How to prevent password saving:

To prevent the browser from saving passwords (and usernames), you need to:

  • copy username and password to hidden form fields before submitting the login form
  • clear the visible username and password fields
  • set autocomplete=off for good measure

This makes the browser attempt to save empty credentials, or not save at all.

A login form might look like this:

<form action='/login' class='login-form' autocomplete='off'> Email: <input type='email' name='email-entry'> <input type='hidden' name='email'> Password: <input type='password' name='password-entry'> <input type='hidden' name='password'> </form> <script> $('.login-form').on('submit', function() { $('[name="email"]').val($('[name="email-entry"]').val()); $('[name="email-entry"]').val(''); $('[name="password"]').val($('[name="password-entry"]').val()); $('[name="password-entry"]').val(''); }); </script>

What about simply using autocomplete=off?

Recent versions of all major browsers (Chrome, Firefox, IE) will all ignore autocomplete=off on login forms (and sometimes in other places, causing much mayhem).

There are workarounds for this (see Chrome 34+, Firefox 38+, IE11+ ignore autocomplete=off), but those will not improve security.
They work by tricking the browsers to fill in fake invisible inputs, instead of the real ones. An attacker with control over a victim's browser can simply use JavaScript or web developer tools to retrieve values from those inputs.

Once an application no longer requires constant development, it needs periodic maintenance for stable and secure operation. makandra offers monthly maintenance contracts that let you focus on your business while we make sure the lights stay on.

Owner of this card:

Tobias Kraze
Last edit:
over 6 years ago
by Tobias Kraze
About this deck:
We are makandra and do test-driven, agile Ruby on Rails software development.
License for source code
Posted by Tobias Kraze to makandra dev
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