Non-Template Content Is Implicitly Default Slot Content

Impact: LOW - When using named slots, any top-level content not wrapped in a <template> tag is automatically treated as default slot content. This implicit behavior can cause confusion about where content will render.

Task Checklist

Understand that loose content goes to the default slot
Use explicit <template #default> when clarity matters
Keep slot content organization intentional

The Implicit Behavior:

<script setup>
import BaseLayout from './BaseLayout.vue'
</script>

<template>
  <BaseLayout>
    <template #header>
      <h1>Page Title</h1>
    </template>

    <!-- These are IMPLICITLY in the default slot -->
    <p>First paragraph of main content.</p>
    <p>Second paragraph of main content.</p>

    <template #footer>
      <p>Footer content</p>
    </template>
  </BaseLayout>
</template>

The two <p> elements are automatically placed in <slot> (the default slot) in the child component.

Equivalent Explicit Version:

<template>
  <BaseLayout>
    <template #header>
      <h1>Page Title</h1>
    </template>

    <!-- Explicit default slot -->
    <template #default>
      <p>First paragraph of main content.</p>
      <p>Second paragraph of main content.</p>
    </template>

    <template #footer>
      <p>Footer content</p>
    </template>
  </BaseLayout>
</template>

When Implicit Behavior Causes Confusion

Scattered Content:

<template>
  <BaseLayout>
    <template #header>
      <h1>Title</h1>
    </template>

    <p>Content A</p>  <!-- Goes to default slot -->

    <template #sidebar>
      <nav>Navigation</nav>
    </template>

    <p>Content B</p>  <!-- Also goes to default slot! -->

    <template #footer>
      <p>Footer</p>
    </template>

    <p>Content C</p>  <!-- Also goes to default slot! -->
  </BaseLayout>
</template>

All three <p> elements end up in the default slot together, which may not be the intended order or grouping.

Clearer with Explicit Default:

<template>
  <BaseLayout>
    <template #header>
      <h1>Title</h1>
    </template>

    <template #default>
      <p>Content A</p>
      <p>Content B</p>
      <p>Content C</p>
    </template>

    <template #sidebar>
      <nav>Navigation</nav>
    </template>

    <template #footer>
      <p>Footer</p>
    </template>
  </BaseLayout>
</template>

Best Practices

Scenario	Recommendation
Only default slot used	Implicit is fine
Mixed named + default slots	Consider explicit `#default`
Complex layouts	Always use explicit templates
Team/shared codebase	Prefer explicit for clarity

The Child Component

<!-- BaseLayout.vue -->
<template>
  <div class="layout">
    <header>
      <slot name="header"></slot>
    </header>

    <aside>
      <slot name="sidebar"></slot>
    </aside>

    <main>
      <!-- All implicit content ends up here -->
      <slot></slot>
    </main>

    <footer>
      <slot name="footer"></slot>
    </footer>
  </div>
</template>

Reference

Vue.js Slots - Named Slots

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