@unlazy/nuxt

The Nuxt module provides an auto-imported UnLazyImage component as a drop-in replacement for native <img> and <picture> elements (when using the sources prop).

Installation

Install the @unlazy/nuxt package using your favorite package manager:

pnpm

pnpm add -D @unlazy/nuxt

yarn

yarn add -D @unlazy/nuxt

npm

npm install -D @unlazy/nuxt

Add the @unlazy/nuxt module to your Nuxt configuration:

// `nuxt.config.ts`
export default defineNuxtConfig({
  modules: ['@unlazy/nuxt']
})

Module Options

export interface ModuleOptions {
  /**
   * Whether to generate the blurry placeholder on the server-side if a BlurHash
   * or ThumbHash is provided via the `blurhash`, respectively `thumbhash` prop.
   *
   * @default true
   */
  ssr?: boolean

  /**
   * The size of the longer edge (width or height) of the BlurHash image to be
   * decoded, depending on the aspect ratio.
   *
   * @remarks
   * This option is ignored if a ThumbHash is used.
   *
   * @default 32
   */
  placeholderSize?: number
}

Set the options under the unlazy key:

// `nuxt.config.ts`
export default defineNuxtConfig({
  modules: ['@unlazy/nuxt'],

  // Module options
  unlazy: {
    ssr: false
  }
})

WARNING

With ssr: false, the placeholder is decoded in the browser and only appears after hydration instead of on first paint.

UnLazyImage Component

The UnLazyImage component is globally available in your Nuxt application.

Props

Prop	Type	Default	Description
src	String	-	Image source URL to be lazy-loaded.
srcSet	String	-	Image source set to be lazy-loaded.
sources	Array	-	Array of UnLazySource objects to render a <picture> element.
autoSizes	Boolean	false	Whether the sizes attribute should be automatically calculated.
blurhash	String	-	A BlurHash string representing the blurry placeholder image.
thumbhash	String	-	A ThumbHash string representing the blurry placeholder image. If both are provided, thumbhash takes precedence.
placeholderSrc	String	-	Optional image source URL for a custom placeholder image. Ignored if a hash is provided.
placeholderSize	Number	32	The size of the longer edge for BlurHash decoding. Ignored for ThumbHash.
placeholderRatio	Number	-	Aspect ratio (width / height) for BlurHash decoding. Without it, the server decodes a square placeholder.
lazyLoad	Boolean	true	Whether the image should be lazy-loaded. Set to false to defer loading until changed to true.
preload	Boolean	false	Whether the image should be preloaded immediately, bypassing lazy loading.
ssr	Boolean	Module option ssr	Whether hashes should be decoded on the server. Overrides the module option.
loading	String	'lazy'	Loading strategy for the image ('lazy' or 'eager'). Defaults to 'eager' while lazyLoad is false.

The component also accepts all standard <img> HTML attributes via Nuxt's attribute inheritance.

Emitted Events

Event	Payload	Description
image-load	HTMLImageElement	Fired once when the real image finishes loading.
image-error	HTMLImageElement, Event	Fired when the preload fails.

INFO

Native @error listeners attach to the underlying <img> via Vue's attribute fallthrough and fire for both browser-level errors and the synthetic event unlazy dispatches when its preload fails. Reach for @image-error when you want the unwrapped element with a typed payload.

Examples

In every srcSet example, the auto-sizes prop calculates the sizes attribute automatically.

Inlined Placeholder Image

<UnLazyImage
  placeholder-src="data:image/svg+xml, ..."
  src="/foo/bar.jpg"
/>

BlurHash

<UnLazyImage
  :blurhash="blurhash"
  :placeholder-ratio="2"
  src-set="image-320w.jpg 320w, image-640w.jpg 640w"
  auto-sizes
  width="640"
  height="320"
/>

For a ThumbHash, pass :thumbhash instead of :blurhash and drop :placeholder-ratio. Add :ssr="false" to decode the hash in the browser.

INFO

When using client-side BlurHash decoding (:ssr="false"), set explicit width and height attributes. See Hash-Based Placeholders for why.

Multiple Image Sources

Pass sources to render a <picture> element with format negotiation and art direction. Each entry becomes a <source> child:

<script setup lang="ts">
import type { UnLazySource } from 'unlazy'

const sources: UnLazySource[] = [
  { type: 'image/avif', srcSet: 'hero.avif 1x, hero@2x.avif 2x' },
  {
    media: '(max-width: 600px)',
    srcSet: 'hero-mobile.jpg',
    width: 480,
    height: 640,
  },
]
</script>

<template>
  <UnLazyImage
    src="/hero.jpg"
    :sources="sources"
    width="640"
    height="427"
  />
</template>

TIP

Set width and height per source to prevent layout shift when the breakpoint changes. Modern browsers use the matched <source>'s dimensions for the rendered <img>'s aspect ratio.

Preload Image

Set preload to load the image before it enters the viewport, for example the next slide of a slider:

<template>
  <UnLazyImage
    width="640"
    height="320"
    :blurhash="blurhash"
    src-set="image-320w.jpg 320w, image-640w.jpg 640w"
    auto-sizes
    preload
  />
</template>