In modern browsers, your previous entries in many Web forms is stored by your computer so you can re-enter it quickly should you need to do so in the future. Because the search bar on Google's website is simply a form to be completed, from your browser's point of view, search history is stored on your computer. You can delete your Google history quickly by clearing your browser's memory.
Load Internet Explorer. Click “Tools” on the menu bar and select “Internet Options”. Select the “General” tab and click “Delete” under the “Browser History” options. Un-check all the check boxes except for “Delete forms”. Click “Yes”. If you leave any other check boxes checked, those items (such as your recently visited websites) will be deleted too. Close Internet Explorer.
Open Firefox. Click the “Tools” menu on the menu bar. Select “Options” from the drop-down menu. Click the “Privacy” icon to view the “Privacy” tab. Select “Clear now” and un-check everything but “Saved Form and Search History”. Again, if you leave any other check boxes checked, those items will be deleted also. Click the “Clear private data now” button. Close Firefox.
Open Safari. Click the “File” menu (or the “Safari” menu on a Mac) and select “Preferences”. Click the “Autofill” tab. Click “Edit”. Scroll down the list of sites that Safari is keeping “Autofill” data on until you find “Google”. Select it. Click “Remove”. If there are several entries for Google (such as google.com and google.co.uk), remove each in turn. Click “Done”. Close Safari.
Open Google Chrome. Click on the “wrench” button on the menu bar, to the right of the address bar. If the “wrench” button is not there on your OS X version, click the “Chrome” menu. Select “Clear browsing Data”. Tick the “Clear browsing history” check box and click the “Clear data for this period” menu. Select the “everything” option. Click “Clear browsing data”. Close Chrome.
Because Google search history is a stored as “Autofill” data, clearing your search history will also remove all other auto-complete form data, such as your auto-completed login details for websites. Be sure to keep a record of your usernames for these websites, if you do not already know them by heart. Do not keep a written record of your important passwords for these sites, however, as this creates large security problems.