Display Blurry Placeholders While Loading Images – unlazy

Preview:

Description:

unlazy is an SEO-friendly and framework-agnostic lazy loading library that displays a blurry image placeholder until the original image is completely loaded.

It works with the native loading=”lazy” attribute and uses the Intersection Observer API to detect when an image enters the viewport.

unlazy allows you to initially load low-quality blurry placeholder images and smoothly transition them to full-resolution images as they scroll into view. It supports BlurHash or ThumbHash placeholders both on the client side and server-side (during server-side rendering), which allows you to use BlurHash as a placeholder for images that have not yet loaded.

In addition, the library is easy to integrate into popular JS frameworks like React, Vue,js, Solid, etc.

How to use it:

1. Install and import the unlazy.

# Yarn
$ yarn add unlazy
# NPM
$ npm i unlazy

import { lazyLoad } from 'unlazy'
// initialize the unlazy
lazyLoad()

<!-- OR --&gt;
<script src="https://unpkg.com/unlazy" defer init></script>

2. Add the blurry placeholder to the src attribute.

<img
  loading="lazy"
  src="data:image/svg+xml, ..."
>

3. Specify the path to the original image(s) using the data-srcset attribute.

<img
  loading="lazy"
  src="data:image/svg+xml, ..."
  data-srcset="1x.png 1024w, 2x.png 2048w"
  data-sizes="auto"
  width="1024"
  height="768"
>

4. It also works with the picture tag.

<picture>
  <source
    loading="lazy"
    src="data:image/svg+xml, ..."
    data-srcset="original.jpg"
    media="(min-width: 800px)"
  >
</picture>

5. Use BlurHash or ThumbHash to generate blurry placeholders.

<img
  data-srcset="https://source.unsplash.com/EBtfyalTU50/2400x1600"
  data-blurhash="LKO2:N%2Tw=w]~RBVZRi};RPxuwH"
  loading="lazy"
  data-sizes="auto"
  width="1024"
  height="768"
  style="aspect-ratio: 4/3"
  alt="Image with blurry placeholder"
>

<img
  data-src="image.jpg"
  data-thumbhash="1QcSHQRnh493V4dIh4eXh1h4kJUI"
>

Changelog:

v0.12.x (03/26/2025)

• Bugfixes
• Allow overwriting loading prop

v0.11.5/6/7/8 (11/12/2024)

• Bugfixes
• Use current date for placeholder id as well
• Outsource check for descendant of picture

v0.11.4 (11/08/2024)

• Bugfixes

v0.11.3 (04/04/2024)

• Bugfixes
• Move from Buffer to Uint8Array

v0.11.2 (03/11/2024)

• Bugfixes

v0.11.1 (02/19/2024)

• nuxt: Emit error event
• vue: Emit error event

v0.11.0 (02/18/2024)

• Ensure image pre load event is called once
• Bugfixes

v0.10.5 (02/18/2024)

• Update sources to prevent duplicate downloads

v0.10.4 (01/07/2024)

• vue,nuxt: loaded event when image is loade

v0.10.3 (01/03/2024)

• Support Svelte 4

v0.10.2 (11/06/2023)

• Rename __ENABLE_HASH_DECODING__ to __UNLAZY_HASH_DECODING__

v0.10.1 (09/12/2023)

• Bugfixed
• Improved performance

v0.10.0 (09/11/2023)

• Bugfixes

v0.9.5 (09/09/2023)

• Don’t expose internal updateSizesAttribute
• core: Respect image sizes if present
• core: Add cleanup handler only if resize handler initiated
• nuxt: Use autoSizes to calculate sizes for preloading
• vue: Use autoSizes to calculate sizes for preloading

v0.9.4 (09/07/2023)

• Expose updateSizesAttribute
• Bugfixes

v0.9.3 (09/01/2023)

• Update

v0.9.1 (07/19/2023)

• Update sizes attribute on image resize with new value

v0.9.1 (07/07/2023)

• vue: Add preload prop

v0.9.0 (06/20/2023)

• Bugfix & Update

v0.8.9 (05/08/2023)

• Bugfixes

v0.8.8 (04/25/2023)

• Bugfixes

v0.8.4 (04/25/2023)

• Bugfixes
• components: src an srcSet props for lazy loading

v0.8.1 (04/25/2023)

• Remove immediate option
• nuxt: lazyLoad prop for data saving mode etc.
• added Svelte component

v0.7.6 (04/24/2023)

• components: immediate prop
• bugfixes

v0.7.0 (04/22/2023)

• ThumbHash support