WordPress—deregister built-in webfonts

functions.php

// deregister Bitter and Open Sans webfonts only
function deregister_default_fonts() {
    wp_deregister_style( 'twentythirteen-fonts' );
}
add_action( 'wp_enqueue_scripts', 'deregister_default_fonts', 100 );

// remove default fonts, add custom fonts, and use a custom minified stylesheet and register but don’t enqueue style.css with all the theme information
function add_custom_css() {
    wp_enqueue_style( 'theme-style', get_stylesheet_directory_uri() . '/style.min.css' );
    wp_dequeue_style( 'twentythirteen-style' );

    // fonts
    wp_dequeue_style( 'twentythirteen-fonts' );
    wp_deregister_style( 'open-sans' );
    wp_register_style( 'open-sans', false ); // dependency workaround from https://gist.github.com/thetrickster/8946567
    wp_dequeue_style( 'bitter' );

    wp_enqueue_style( 'webfonts', '//fonts.googleapis.com/css?family=Alegreya+Sans:400,700,400italic|Alegreya:400,700' );
}
add_action( 'wp_print_styles', 'add_custom_css' );