Sass meta.mixin-exists() Function

What You’ll Learn

meta.mixin-exists() belongs to the built-in sass:meta module. It answers a simple question: is there a mixin named X? This page covers $module with @use, optional include patterns, safer alternatives to deprecated meta.feature-exists, and five compiled examples.

What Is meta.mixin-exists()?

Official docs: returns whether a mixin named $name exists. Use it when a library or theme wants an optional @mixin without crashing if that mixin is missing.

• Without $module, Sass looks for a mixin without a namespace in the current file.
• With $module, it looks inside a @use namespace from the current file.
• Missing names return false—they do not throw.

📝 Syntax

@use "sass:meta";

// Recommended
meta.mixin-exists($name, $module: null)

// Legacy global name (no $module argument)
mixin-exists($name)

Parameters

Return value

📦 Loading sass:meta

// Recommended — namespaced
@use "sass:meta";
@use "utils";
$ok: meta.mixin-exists("center", $module: "utils");

// Optional — bring members into scope
@use "sass:meta" as *;
$ok: mixin-exists("shadow-none");

// Legacy global
$ok: mixin-exists("shadow-none");

🔗 Using the $module Argument

After @use "utils", mixins from that file live under the utils namespace. Check them with a module name:

@use "sass:meta";
@use "utils";

// Official style (positional $module)
@debug meta.mixin-exists("center", "utils"); // true

// Equivalent named argument
@debug meta.mixin-exists("center", $module: "utils"); // true

// Without $module, "center" is not defined in this file
@debug meta.mixin-exists("center"); // false

$module must match the namespace used in the current file. If you write @use "utils" as u, pass $module: "u".

📋 Related Meta Helpers

🛠 Compatibility

This is about Sass compilers, not browsers. The lookup runs at compile time.

Prefer current Dart Sass so @use namespaces work as shown in the docs.

Examples Gallery

Each example uses meta.mixin-exists at compile time. Open View Compiled CSS for verified Dart Sass output.

@use "sass:meta";

.before {
  --shadow: #{meta.mixin-exists("shadow-none")};
}

@mixin shadow-none {
  box-shadow: none;
}

.after {
  --shadow: #{meta.mixin-exists("shadow-none")};
}

.btn {
  @include shadow-none;
}

.before {
  --shadow: false;
}

.after {
  --shadow: true;
}

.btn {
  box-shadow: none;
}

@mixin center {
  display: grid;
  place-items: center;
}

@use "sass:meta";
@use "utils";

.probe {
  --utils-center: #{meta.mixin-exists("center", $module: "utils")};
  --bare-center: #{meta.mixin-exists("center")};
}

.probe {
  --utils-center: true;
  --bare-center: false;
}

@use "sass:meta";

@mixin soft-shadow {
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.12);
}

@mixin card($pad: 1rem) {
  @if meta.mixin-exists("soft-shadow") {
    @include soft-shadow;
  }
  padding: $pad;
}

.panel {
  @include card(1.25rem);
}

.panel {
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.12);
  padding: 1.25rem;
}

@use "sass:meta";

@mixin elevate {
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.16);
}

$name: "elevate";

.card {
  @if meta.mixin-exists($name) {
    @include meta.apply(meta.get-mixin($name));
  } @else {
    box-shadow: none;
  }
}

.card {
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.16);
}

@use "sass:meta";
@use "utils";

.flags {
  --nope: #{meta.mixin-exists("definitely-missing")};
  --typo: #{meta.mixin-exists("centerr", $module: "utils")};
  --ok: #{meta.mixin-exists("center", $module: "utils")};
}

.flags {
  --nope: false;
  --typo: false;
  --ok: true;
}

🚀 Real-World Use Cases

• Optional theme hooks — include a user-provided @mixin only if it exists.
• Module-aware libraries — detect mixins from a @use namespace via $module.
• Safe dynamic APIs — guard meta.get-mixin + meta.apply.
• Migration off feature-exists — preferred modern detection for mixin APIs.
• Plugin registries — enable style features when a named mixin is present.

⚠️ Common Pitfalls

• Forgetting $module — a mixin from @use "utils" will not match a bare "center" check.
• Wrong namespace string — must match the @use … as name in this file.
• Confusing with get-mixin — exists returns a boolean; get-mixin returns a value.
• Checking functions — use meta.function-exists instead.
• Expecting runtime checks — everything resolves when Sass compiles.

💡 Best Practices