- Open your Firefox browser.
- Left click from the top toolbar Tools and then Options. The Options window will then load.
- Then left click the Privacy icon from the left pane of the Options window.

- From the right pane click the Clear button next to "Saved Form Information".
If you decide that you no longer wish for Firefox to use its
autocomplete functionality in the Search bar you can stop this by
clicking on the plus sign next to "Saved Form Information". Then untick
the checkbox entitled "Save information I enter in web page forms and
the Search Bar". Should you change your mind you can turn this
functionality back on by simply reticking this checkbox.