This attribute applies either to the <form> element or on individual <input> elements. It specifies when input fields must autocomplete the user's input based on the user's typing history.
Possible values of this attribute: on/off.
If applied to the <form> element, all input fields attached to the form (inside or linked to it using the form attribute), will have auto-completion set by default to the value of the autocomplete attribute of the form.
This default behavior can be overridden by setting it individually to any input field inside. In other words: it is possible to have autocomplete "on" for the form, and "off" for specific input fields, or vice-versa.
Sometimes this autocomplete behavior is disabled by default in some Web browsers, and will need to be adjusted in the preferences/settings.
This attribute targets most input types (those that allow typing in them).
Source code extract:
<form submit="test.php" method="post" autocomplete="on">
...
<label for="address">Enter your address (autocomplete off, overrides the
form's autocomplete=on attribute):</label>
<input type="text" id="address" autocomplete="off">
<p>
<label for="address1">Enter your address (autocomplete on by inheritance of
the form's autocomplete=on attribute):</label>
<input type="text" id="address1">
<p>
<button type="submit">Submit</button>
...
</form>