Blog › Render-blocking resources
What are render-blocking resources and how do you fix them?
A render-blocking resource is a file that the browser has to fully download and process before it will show anything on screen. While that file is loading, visitors see a blank white page. Render-blocking issues are one of the most common reasons sites score poorly on First Contentful Paint — the measure of how quickly something appears.
What does “render-blocking” actually mean?
When someone visits your site, the browser reads your page top to bottom and loads files as it goes. Most files — images, for example — load in the background while the page is already being displayed. But certain files, particularly scripts and stylesheets, cause the browser to stop and wait before showing anything.
Imagine a restaurant that won’t let any customers sit down until all the menus have been printed, even though the kitchen is already ready. The page is ready, but the browser is waiting for files before it will show it.
This is by design for stylesheets — browsers need your styles before they can display the page correctly. The problem is when those files are large, slow to load, or there are too many of them. Scripts are more problematic: most scripts don’t need to run before the page is visible, but if they’re set up incorrectly, they cause the same block.
How serious is it?
On a typical site with several blocking scripts, this issue can add 1–3 seconds to the time before anything appears on screen. On slower mobile connections the impact is even greater. It directly affects your First Contentful Paint score and, in turn, your overall performance score and search ranking.
If PageWeight shows render-blocking resources in your results, it’s worth addressing — it’s usually one of the quicker wins once you know what to ask for.
What causes render-blocking issues?
The most common causes are:
- Scripts loaded at the start of the page — analytics tools, advertising pixels, and other third-party code that loads early, before the page is visible
- Large stylesheet files — CSS files that include styles for the entire site loaded on every single page, even when most of those styles aren’t needed
- Web fonts — custom fonts that block text from rendering until the font file arrives
- Page builder scripts — many WordPress page builders load large amounts of JavaScript and CSS on every page as part of how they work
How to fix it
If your site runs on WordPress
A performance plugin can handle most of this without any developer involvement. WP Rocket, Perfmatters, and LiteSpeed Cache all have settings to delay scripts so they load after the page is already visible, and to optimize how stylesheets are delivered. Most have a one-click setup that addresses the most common render-blocking issues automatically.
If you’re using a page builder like Elementor or Divi, check whether it has a built-in performance mode — recent versions of both include options to reduce the scripts and styles they load.
On any other platform
This is a developer task, but it’s a straightforward one. Show your developer your PageWeight results and ask them to:
- Make non-essential scripts load after the page is visible rather than at the start (this is a one-line change per script in most cases)
- Check whether any large stylesheet files can be split so pages only load the styles they actually need
- Ensure web fonts are set to display text immediately using a fallback font while the custom font loads
These are standard optimizations that any experienced developer will be familiar with. The PageWeight results give them a specific list of which files are causing the issue, which makes the job much faster.