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Viewport Extra is a library that enables setting the minimum / maximum width of the viewport. It reduces the range of the viewport that needs to be considered when styling.

For example, when displaying a 412px-wide page on a mobile browser with a viewport width of 360px (e.g., Chrome on Galaxy S24 in portrait mode), horizontal scrolling occurs. This can be resolved by styling for viewport widths less than 412px, but it's a hassle. However, by using Viewport Extra to set the minimum viewport width to 412px, the page will be scaled down to fit perfectly within 360px, eliminating horizontal scrolling. This provides a simple solution with no styling required.

Page scaling is achieved by updating the content attribute of the <meta name="viewport"> element.

• Scale Down Page on Small Viewport Widths
• Scale Up Page on Large Viewport Widths
• Set Different Minimum / Maximum Widths per Media Query
• Rescale Page When Viewport Width Changes

Pages containing the following code are scaled down on mobile browsers with viewport widths less than 412px, but are not scaled down on other browsers. Whether to scale down is determined only once when the pages are displayed (Reference).

<meta name="viewport" content="width=device-width,initial-scale=1">
<meta name="viewport-extra" content="min-width=412">

<script async src="https://cdn.jsdelivr.net/npm/[email protected]/dist/iife/viewport-extra.min.js"></script>

import("viewport-extra").then(({ setContent }) => {
  setContent({ minWidth: 412 })
})

initial-scale=0.8737864077669902,width=412

initial-scale=0.9538834951456311,width=412

initial-scale=1,width=device-width

initial-scale=1,width=device-width

initial-scale=1,width=device-width

Pages containing the following code are scaled up on mobile browsers with viewport widths greater than 393px, but are not scaled up on other browsers. Whether to scale up is determined only once when the pages are displayed (Reference).

<meta name="viewport" content="width=device-width,initial-scale=1">
<meta name="viewport-extra" content="max-width=393">

<script async src="https://cdn.jsdelivr.net/npm/[email protected]/dist/iife/viewport-extra.min.js"></script>

import("viewport-extra").then(({ setContent }) => {
  setContent({ maxWidth: 393 })
})

initial-scale=1,width=device-width

initial-scale=1,width=device-width

initial-scale=1.0483460559796438,width=393

initial-scale=1.8676844783715012,width=393

initial-scale=2.6055979643765905,width=393

Pages containing the following code are scaled down on mobile browsers with viewport widths less than 412px or between 744px (inclusive) and 1024px (exclusive), but are not scaled down on other browsers. Whether to scale down is determined only once when the pages are displayed (Reference).

<meta name="viewport" content="width=device-width,initial-scale=1">
<meta name="viewport-extra" content="min-width=412">
<meta name="viewport-extra" content="min-width=1024" data-media="(min-width: 744px)">

<script async src="https://cdn.jsdelivr.net/npm/[email protected]/dist/iife/viewport-extra.min.js"></script>

import("viewport-extra").then(({ setParameters }) => {
  setParameters([
    { content: { minWidth: 412 } },
    { content: { minWidth: 1024 }, media: "(min-width: 744px)" },
  ])
})

initial-scale=0.8737864077669902,width=412

initial-scale=1,width=device-width

initial-scale=0.7265625,width=1024

initial-scale=1,width=device-width

Pages containing the following code determine whether to scale up or down not only when displayed but also when the viewport width changes. This is useful in scenarios such as switching between portrait and landscape modes on mobile devices or screen splitting on tablets.

<meta
  name="viewport"
  content="width=device-width,initial-scale=1"
  data-extra-unscaled-computing
>

<script
  async
  src="https://cdn.jsdelivr.net/npm/[email protected]/dist/iife/viewport-extra.min.js"
  id="viewport-extra-script"
></script>

<script>
  const updateViewportMetaEl = () => {
    // To prevent infinite resizing
    new ResizeObserver((_, observer) => {
      observer.unobserve(document.documentElement)
      window.addEventListener("resize", updateViewportMetaEl, { once: true })
    }).observe(document.documentElement)

    ViewportExtra.setParameters([
      { content: { minWidth: 412 } },
      { content: { minWidth: 744 }, media: "(min-width: 640px)" },
    ])
  }
  if (window.ViewportExtra) {
    updateViewportMetaEl()
  } else {
    document
      .getElementById("viewport-extra-script")
      .addEventListener("load", updateViewportMetaEl)
  }
</script>

import("viewport-extra").then(({ setParameters }) => {
  const updateViewportMetaEl = () => {
    // To prevent infinite resizing
    new ResizeObserver((_, observer) => {
      observer.unobserve(document.documentElement)
      window.addEventListener("resize", updateViewportMetaEl, { once: true })
    }).observe(document.documentElement)

    setParameters([
      { content: { minWidth: 412 } },
      { content: { minWidth: 744 }, media: "(min-width: 640px)" },
    ])
  }
  updateViewportMetaEl()
})

initial-scale=0.9538834951456311,width=412

initial-scale=0.9865591397849462,width=744

English | 日本語

The upcoming major version v3, which includes breaking changes, is scheduled for release. To handle this, continuation of using v2 and v1 or migration to v3 release candidate (RC) are available.

v2 and v1 will continue to be maintained and remain available for use even after the release of v3.

In v2.5, during the period before and after the release of v3, a message about v3 is displayed in the web browser console. The following code can suppress the message.

<meta
  name="viewport"
  content="width=device-width,initial-scale=1"
  data-extra-no-migration-message
>

Ahead of the v3 stable release, the v3 release candidate (RC) and the migration guides to v3 have been published.

• Reference: Migration Guide from v2 to v3
• Reference: Migration Guide from v1 to v3

The release candidate (RC) can be used to migrate to v3, as no breaking changes are planned from v3.0.0-rc.2 until the stable release.

• Using the following style together is recommended to prevent browsers on small mobile devices from unexpectedly changing the text size (Reference).

  body {
    -webkit-text-size-adjust: 100%;
  }

• When testing with developer tools of desktop browsers, mobile device simulation must be enabled and the viewport must be set to the desired size before navigating to a page that uses Viewport Extra. If the order is reversed, the browser may ignore the initial-scale setting of the <meta name="viewport"> element. This behavior is specific to simulation in developer tools and does not occur in actual mobile browsers.