Take a look in header.php of your theme. Some themes have the title output like this: <title><?php wp_title(‘|’, true, ‘right’); ?> | <?php echo get_bloginfo(‘name’) ?></title> So you’ll have to remove the | <?php echo get_bloginfo(‘name’) ?> part. However you should keep the title of the site in the <title> for SEO purposes.
If your theme supports WordPress adding the title tag using add_theme_support( ‘title-tag’ ); (it should!) you can use the document_title_parts filter to insert the post count in the right place without needing to parse the full title or modify existing elements that might have been customised, such as the separator: function wpse_323260_document_title_category_count( $title ) { … Read more
UPDATE for WordPress 4.4 Since WordPress 4.4 the wp_title filter doesn’t work because wp_title() function is not used in core anymore. That function was marked as deprecated, then reinstated until new notice but theme authors are discouraged from using it. Because of that, wp_title filter still will work if you continue using wp_title() function directly … Read more