Add title description keyword meta tag without using plugin in wordpress

The search bots will search for necessary information for users based on the meta tags’ and the article’s content. The page or post will rank higher in search result pages if its meta tags contain important keywords. Therefore, it should be concise and contain important keywords. It will be better for SEO if you can put the keyword to the beginner of the description is better.

Description and keyword without plugin
Paste this in theme’s functions.php file.

function add_meta_tags() {
    global $post;
    if ( is_single() ) {
        $meta = strip_tags( $post->post_content );
        $meta = strip_shortcodes( $post->post_content );
        $meta = str_replace( array("\n", "\r", "\t"), ' ', $meta );
        $meta = substr( $meta, 0, 125 );
        $keywords = get_the_category( $post->ID );
        $metakeywords = '';
        foreach ( $keywords as $keyword ) {
            $metakeywords .= $keyword->cat_name . ", ";
        }
        echo '<meta name="description" content="' . $meta . '" />' . "\n";
        echo '<meta name="keywords" content="' . $metakeywords . '" />' . "\n";
    }
}
add_action( 'wp_head', 'add_meta_tags' , 2 );

function gretathemes_meta_description() {
    global $post;
    if ( is_singular() ) {
        $des_post = strip_tags( $post->post_content );
        $des_post = strip_shortcodes( $post->post_content );
        $des_post = str_replace( array("\n", "\r", "\t"), ' ', $des_post );
        $des_post = mb_substr( $des_post, 0, 300, 'utf8' );
        echo '<meta name="description" content="' . $des_post . '" />' . "\n";
    }
    if ( is_home() ) {
        echo '<meta name="description" content="' . get_bloginfo( "description" ) . '" />' . "\n";
    }
    if ( is_category() ) {
        $des_cat = strip_tags(category_description());
        echo '<meta name="description" content="' . $des_cat . '" />' . "\n";
    }
}
add_action( 'wp_head', 'gretathemes_meta_description');

Title tag without plugin

<title><?php wp_title(' | ', 'echo', 'right'); ?><?php bloginfo('name'); ?></title>