WordPress 5.9 improves lazy loading largest content paint

WordPress 5.9 is all set to release on January 25, 2022.

This is going to be the first version of WordPress that supports full-site editing (with block-based themes) in its core.

The version also comes with several performance improvements.

But we classify them into two categories.

  1. Editor Performance
  2. Front End Performance

Let’s talk about them in detail.

Editor’s Performance

The editor is the most vital part of WordPress.

It helps us to compose our posts and pages, insert blocks, patterns, etc.

WordPress 5.9 comes with several editor improvements listed below.


Ever since the introduction of Blocks and Patterns in WordPress, we have frequently used the Inserter tool.

It helps us to select blocks and patterns and insert them in posts and pages.

WordPress 5.9 has optimized the inserter tool and make it super quick.

It lazy-render the two instances of the inserter tool.

  1. When selecting blocks and patterns.
  2. When displaying categories.

Both these improvements will provide a better experience. It helps to quickly open the inserter tool.

Reusable Blocks

A Reusable block is a content block saved to be used later.

When we often use the same content snippet then we can use a Reusable block. For example, a call to action button at the end of the post.

There is no issue when we have a few reusable blocks on our site.

But what about when we have thousands of reusable blocks.

Well, WordPress 5.9 has improved the same.

It uses a method that makes the reusable blocks faster, even if we have thousands of them.

List View

List View is a tool in WordPress that helps us to navigate between layers of contents and blocks.

You can access the list view tool in WordPress from the top of the editor’s toolbar.

List View Tool in WordPress Editor
List View Tool in WordPress Editor

WordPress 5.9 has improved the performance of the List View tool as well.

It uses a windowing technique that renders a fixed number of items at a time.

It scales itself with the content.

Front End Performance

While so far, we talked about the back-end performance let’s talk about the performance improvements in the Front end.

Let’s learn what are all the improvements that visitors of our site will feel.

Block Themes

As I told you above, WordPress 5.9 is the first version to support full-site editing via block-based themes.

The advantage of the block theme is we have only a theme.json file where we place all the stylesheets of our website.

Block Stylesheets

In the earlier release, the stylesheets of all the blocks were placed in a single file that results in an extra page load.

WordPress 5.9 has removed the same. It only loads the CSS of blocks that are required while viewing the content.

This way cuts down the amount of CSS loaded which in turn will dramatically increase the loading time of the frontend.

Additional Styles Per Block

Theme developers can now add stylesheets on a per-block basis.

For that they have to use the function – wp_enqueue_block_style().

The above function allows them to register the stylesheets on a per-block basis.

Image Lazy Loading Improvement

WordPress 5.9 has improved the lazy loading time of images.

I already talked about it in detail in this article.

Performance Statistics

In WordPress 5.9, the time to:

  1. Load the first block is 3184.38 ms.
  2. Type a character is 41.52 ms.
  3. Select a block is 101.89 ms.
  4. Open the global inserter is 37.87 ms.
  5. Type in the inserter search input is 73.26 ms.
  6. Move the mouse between two block items in the inserter is 26.23 ms.

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