cssinternet-explorer-11polyfills

IE11 - does a polyfill / script exist for CSS variables?

I'm developing a webpage in a mixed web browser environment (Chrome/IE11). IE11 doesn't support CSS variables, is there a polyfill or script that exists that would allow me to use CSS variables in IE11?

Solution

  • Yes, so long as you're processing root-level custom properties (IE9+).

    From the README:

    Features

    • Client-side transformation of CSS custom properties to static values
    • Live updates of runtime values in both modern and legacy browsers
    • Transforms <link>, <style>, and @import CSS
    • Transforms relative url() paths to absolute URLs
    • Supports chained and nested var() functions
    • Supports var() function fallback values
    • Supports web components / shadow DOM CSS
    • Watch mode auto-updates on <link> and <style> changes
    • UMD and ES6 module available
    • TypeScript definitions included
    • Lightweight (6k min+gzip) and dependency-free

    Limitations

    • Custom property support is limited to :root and :host declarations
    • The use of var() is limited to property values (per W3C specification)

    Here are a few examples of what the library can handle:

    Root-level custom properties

    :root {
    --a: red;
}

p {
    color: var(--a);
}

    Chained custom properties

    :root {
    --a: var(--b);
    --b: var(--c);
    --c: red;
}

p {
    color: var(--a);
}

    Nested custom properties

    :root {
    --a: 1em;
    --b: 2;
}

p {
    font-size: calc(var(--a) * var(--b));
}

    Fallback values

    p {
    font-size: var(--a, 1rem);
    color: var(--b, var(--c, var(--d, red))); 
}

    Transforms <link>, <style>, and @import CSS

    <link rel="stylesheet" href="/absolute/path/to/style.css">
<link rel="stylesheet" href="../relative/path/to/style.css">

<style>
    @import "/absolute/path/to/style.css";
    @import "../relative/path/to/style.css";
</style>

    Transforms web components / shadow DOM

    <custom-element>
  #shadow-root
    <style>
      .my-custom-element {
        color: var(--test-color);
      }
    </style>
    <div class="my-custom-element">Hello.</div>
</custom-element>

    For the sake of completeness: w3c specs

    (Shameless self-promotion: Check)