{"id":17481,"date":"2021-11-11T11:00:56","date_gmt":"2021-11-11T17:00:56","guid":{"rendered":"https:\/\/www.dotcom-tools.com\/web-performance\/?page_id=17481"},"modified":"2021-11-11T11:00:56","modified_gmt":"2021-11-11T17:00:56","slug":"parallelize-downloads-across-hostnames","status":"publish","type":"page","link":"https:\/\/www.dotcom-tools.com\/web-performance\/pagespeed\/parallelize-downloads-across-hostnames\/","title":{"rendered":"PageSpeed Optimizations &#8211; Parallelize Downloads Across Hostnames"},"content":{"rendered":"<p>[vc_row full_width=&#8221;stretch_row&#8221; gap=&#8221;25&#8243; equal_height=&#8221;yes&#8221; content_placement=&#8221;middle&#8221; css=&#8221;.vc_custom_1636408663624{padding-top: 100px !important;padding-bottom: 100px !important;background-image: url(https:\/\/www.dotcom-tools.com\/blog\/wp-content\/uploads\/2015\/09\/hero-section-with-description-3320.jpg?id=15799) !important;background-position: center !important;background-repeat: no-repeat !important;background-size: cover !important;}&#8221;][vc_column css=&#8221;.vc_custom_1636409653940{padding-top: 30px !important;padding-bottom: 30px !important;background-color: #e6eaef !important;}&#8221;][vc_custom_heading text=&#8221;<b>Parallelize Downloads Across Hostnames (Deprecated)<\/b>&#8221; font_container=&#8221;tag:h1|font_size:40|text_align:center|color:%232b2b2b|line_height:1.5&#8243; use_theme_fonts=&#8221;yes&#8221; css=&#8221;.vc_custom_1636649987019{padding-top: 30px !important;padding-bottom: 30px !important;}&#8221;][\/vc_column][\/vc_row][vc_row margin_top=&#8221;40&#8243; margin_bottom=&#8221;30px&#8221; css=&#8221;.vc_custom_1636409410012{margin-bottom: 30px !important;}&#8221;][vc_column][vc_custom_heading text=&#8221;What is Hostname Parallelization?&#8221; font_container=&#8221;tag:h2|font_size:35|text_align:center|color:%232b2b2b|line_height:1.5&#8243; use_theme_fonts=&#8221;yes&#8221;][vc_column_text]<\/p>\n<p style=\"text-align: left;\">Hostname parallelization, also referred to as sharding, is the process of distributing web page resources across multiple subdomains. For example, css.examplesite.com for a set of CSS files or js.examplesite.com for a handful of JavaScript files, and the same for images, and so on. The reason behind this is that browsers can handle, on average, between 4-6 concurrent connections per domain. So, by distributing the load across multiple subdomains, browsers can then manage more concurrent connections at one time. So, if you were to imagine having all these resources on the same domain, it would take longer because they would have to wait for a connection to open. Using hostname parallelization allows these resources to download in parallel, hence the name thereby reducing load times. However, one drawback is that because you are splitting resources across different subdomains, it does add additional DNS lookups.<\/p>\n<p>[\/vc_column_text][vc_custom_heading text=&#8221;Why is Hostname Parallelization Deprecated?&#8221; font_container=&#8221;tag:h3|font_size:30|text_align:center|color:%232b2b2b|line_height:1.5&#8243; use_theme_fonts=&#8221;yes&#8221;][vc_column_text]<\/p>\n<p style=\"text-align: left;\">The reason that PageSpeed has deprecated this optimization is due to the shift from HTTP\/1.1 to HTTP\/2. When HTTP\/2 came along, it improved upon how HTTP\/1.1 prioritized content, making it much faster and more efficient. HTTP\/1.1 is still used today, but as HTTP\/2 grew, there was no longer a need for this optimization. So, the recommendation is to try to reduce or combine your CSS and JavaScript files externally or use image and CSS sprites. Or discontinue using HTTP\/1.1 altogether and upgrade your web server to HTTP\/2.<\/p>\n<p>[\/vc_column_text][\/vc_column][\/vc_row][vc_row margin_top=&#8221;60&#8243; margin_bottom=&#8221;0&#8243; css=&#8221;.vc_custom_1636595147911{margin-bottom: 15px !important;}&#8221;][vc_column width=&#8221;1\/3&#8243; css=&#8221;.vc_custom_1636595227743{padding-top: 60px !important;padding-bottom: 60px !important;padding-left: 10px !important;background-color: #f6f6f6 !important;}&#8221;][vc_single_image image=&#8221;17233&#8243; alignment=&#8221;center&#8221; style=&#8221;vc_box_rounded&#8221;][vc_custom_heading text=&#8221;<b>Lighthouse<\/b>&#8221; font_container=&#8221;tag:p|font_size:20|text_align:center|color:%232b2b2b|line_height:1&#8243; use_theme_fonts=&#8221;yes&#8221;][vc_column_text]<\/p>\n<p style=\"text-align: center;\">Lighthouse is an open-source tool that is used to run an audit against your web pages and provides scores and suggestions for improving page performance, accessibility, SEO, and more.<\/p>\n<p>[\/vc_column_text][vc_btn title=&#8221;Learn More&#8221; style=&#8221;flat&#8221; color=&#8221;primary&#8221; align=&#8221;center&#8221; i_icon_fontawesome=&#8221;fas fa-location-arrow&#8221; add_icon=&#8221;true&#8221; link=&#8221;url:https%3A%2F%2Fwww.dotcom-tools.com%2Fweb-performance%2Flighthouse%2F&#8221;][\/vc_column][vc_column width=&#8221;1\/3&#8243; css=&#8221;.vc_custom_1636595173585{padding-top: 60px !important;padding-bottom: 60px !important;background-color: #f6f6f6 !important;}&#8221;][vc_single_image image=&#8221;17284&#8243; alignment=&#8221;center&#8221; style=&#8221;vc_box_rounded&#8221;][vc_custom_heading text=&#8221;<b>PageSpeed Terms<\/b>&#8221; font_container=&#8221;tag:p|font_size:20|text_align:center|color:%232b2b2b|line_height:1&#8243; use_theme_fonts=&#8221;yes&#8221;][vc_column_text]<\/p>\n<p style=\"text-align: center;\">PageSpeed Insights is a tool created by Google that reports on the performance of a page on both mobile and desktop devices, and provides suggestions on how that page may be improved.<\/p>\n<p>[\/vc_column_text][vc_btn title=&#8221;Learn More&#8221; style=&#8221;flat&#8221; color=&#8221;primary&#8221; align=&#8221;center&#8221; i_icon_fontawesome=&#8221;fas fa-location-arrow&#8221; add_icon=&#8221;true&#8221; link=&#8221;url:https%3A%2F%2Fwww.dotcom-tools.com%2Fweb-performance%2Fpagespeed%2F&#8221;][\/vc_column][vc_column width=&#8221;1\/3&#8243; css=&#8221;.vc_custom_1636595196399{padding-top: 60px !important;padding-right: 10px !important;padding-bottom: 60px !important;background-color: #f6f6f6 !important;}&#8221;][vc_single_image image=&#8221;17281&#8243; alignment=&#8221;center&#8221; style=&#8221;vc_box_rounded&#8221;][vc_custom_heading text=&#8221;<b>YSlow<\/b>&#8221; font_container=&#8221;tag:p|font_size:20|text_align:center|color:%232b2b2b|line_height:1&#8243; use_theme_fonts=&#8221;yes&#8221;][vc_column_text]<\/p>\n<p style=\"text-align: center;\">YSlow is an open-source website analysis tool that can be used to identify web page performance issues. Learn more about the YSlow to enhance your web pages and the user experience.<\/p>\n<p>[\/vc_column_text][vc_btn title=&#8221;Learn More&#8221; style=&#8221;flat&#8221; color=&#8221;primary&#8221; align=&#8221;center&#8221; i_icon_fontawesome=&#8221;fas fa-location-arrow&#8221; add_icon=&#8221;true&#8221; link=&#8221;url:https%3A%2F%2Fwww.dotcom-tools.com%2Fweb-performance%2Fyslow%2F&#8221;][\/vc_column][\/vc_row]<\/p>\n","protected":false},"excerpt":{"rendered":"<p>[vc_row full_width=&#8221;stretch_row&#8221; gap=&#8221;25&#8243; equal_height=&#8221;yes&#8221; content_placement=&#8221;middle&#8221; css=&#8221;.vc_custom_1636408663624{padding-top: 100px !important;padding-bottom: 100px !important;background-image: url(https:\/\/www.dotcom-tools.com\/blog\/wp-content\/uploads\/2015\/09\/hero-section-with-description-3320.jpg?id=15799) !important;background-position: center !important;background-repeat: no-repeat !important;background-size: cover !important;}&#8221;][vc_column css=&#8221;.vc_custom_1636409653940{padding-top: 30px !important;padding-bottom: 30px !important;background-color: #e6eaef !important;}&#8221;][vc_custom_heading text=&#8221;Parallelize Downloads Across Hostnames (Deprecated)&#8221; font_container=&#8221;tag:h1|font_size:40|text_align:center|color:%232b2b2b|line_height:1.5&#8243; use_theme_fonts=&#8221;yes&#8221; css=&#8221;.vc_custom_1636649987019{padding-top: 30px !important;padding-bottom: 30px !important;}&#8221;][\/vc_column][\/vc_row][vc_row margin_top=&#8221;40&#8243; margin_bottom=&#8221;30px&#8221; css=&#8221;.vc_custom_1636409410012{margin-bottom: 30px !important;}&#8221;][vc_column][vc_custom_heading text=&#8221;What is Hostname Parallelization?&#8221; font_container=&#8221;tag:h2|font_size:35|text_align:center|color:%232b2b2b|line_height:1.5&#8243; use_theme_fonts=&#8221;yes&#8221;][vc_column_text] Hostname parallelization, also referred to as sharding,&hellip;<\/p>\n","protected":false},"author":7,"featured_media":0,"parent":17235,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v17.6 (Yoast SEO v19.1) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\r\n<title>PageSpeed Optimizations - Parallelize Downloads Across Hostnames | Dotcom-Monitor Tools Blog<\/title>\r\n<meta name=\"description\" content=\"Using hostname parallelization allows resources to download in parallel, thereby reducing load times. 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