MediaWiki:Common.js

/* Any JavaScript here will be loaded for all users on every page load. */
$(document).ready(function() {
    // Check if we're on the search page
    if (mw.config.get('wgCanonicalSpecialPageName') === 'Search') {
        // Select the desired tab (e.g., "Content pages")
        // The ID for "Content pages" is typically 'mw-search-tab-content'
        $('#mw-search-tab-content').prop('checked', true);

        // Optionally, hide the "Search in namespaces" section (as per your previous request)
        $('.mw-search-profile-tabs').hide();
    }
});