wikipedia-global-site-search-form-improved.html

<form action="/w/index.php" id="searchform" role="search">
    <div id="simpleSearch">
        <label for="searchInput" class="h-hide-visually">Search Wikipedia (shortcut key 
        combination: ctrl-option-f)</label>
        <input type="search" name="search" placeholder="Search" accesskey="f" id="searchInput" 
        tabindex="1" autocomplete="off">
        <input type="hidden" value="Special:Search" name="title">
        <input type="submit" name="go" value="Submit search" id="searchButton" 
        class="searchButton">
    </div>
</form>