---
type: Layout Pattern
name: imposter
title: imposter
category: Overlay / Exception
description: Place an overlay region over a parent without changing document order.
primary_spatial_problem: Place an overlay region over a parent without changing document order.
secondary_spatial_problems: none
layout_axis: both
content_shape: mixed
responsiveness: fixed
constraints: Uses only local class hooks and explicit layout constraints.
scroll_ownership: No internal scroll container.
source_lineage: https://every-layout.dev/layouts/
lifecycle: generated
generated_from: scripts/generate-patterns.mjs, scripts/pattern-data.mjs
---
<!-- Generated from `scripts/generate-patterns.mjs` and `scripts/pattern-data.mjs`. Do not hand-edit generated catalog or pattern docs; edit the source files and regenerate. -->

# imposter

## When To Use

Use this pattern when you need to place an overlay region over a parent without changing document order.

## HTML

```html
<section class="imposter_anchor" aria-label="Draft editor">
    <p>Draft body text stays in normal document flow.</p>
    <section class="imposter" aria-label="Modal placement">
        <dialog open>Unsaved changes confirmation</dialog>
    </section>
</section>
```

## CSS

```css
.imposter_anchor {
    position: relative;
}

.imposter {
    display: grid;
    inset: 0;
    place-items: center;
    position: absolute;
    z-index: 1;
}
```

## Core Properties

- `position`, `display`, `inset`, `place-items`, `z-index` define the spatial behavior for this pattern.

## Properties That Break The Layout If Removed

- Removing `position`, `display`, `inset`, `place-items`, `z-index` changes the pattern from its documented layout responsibility back toward ordinary flow or an unsafe fixed arrangement.

## Constraints And Change Points

- fixed responsiveness is part of the contract; change sizing values only when the new minimum, maximum, or wrap point is documented with the pattern.
- Keep the HTML class hooks and CSS selectors in one-to-one agreement.

## Scroll Ownership

No internal scroll container.

## Accessibility And Source Order Notes

- Semantic role expectation: Preserve the HTML sample's landmark, list, navigation, form, figure, or article roles; layout classes must not replace semantic elements.
- DOM order expectation: Keep semantic elements, DOM order, reading order, and focus order independent from the visual placement created by the layout classes.
- Focus risk: Any interactive descendants follow DOM order; do not use this pattern to create a visual order that keyboard focus cannot follow.
- Scroll expectation: No internal scroll container.
- Cognitive risk: Low: the pattern should preserve ordinary reading flow when semantic order is already correct.

## Browser And Fallback Notes

The CSS uses modern grid, flex, intrinsic sizing, logical properties, or positioning. If a target browser cannot support a property, fall back to ordinary block flow before adding decorative or script-driven layout behavior.

## Composition Notes

Use `imposter` as the stable pattern root and compose additional layout behavior outside that root unless the child class is part of the documented relationship.

## Anti-patterns

- Do not add color, border, shadow, typography, or animation rules to reusable pattern CSS.
- Do not use this pattern to repair unclear HTML structure; make the DOM roles legible first.

## IA Navigation

Parent: [Overlay / Exception patterns](https://style.gallery/materials/v2/pages/patterns/overlay-exception/index.md) in [Pattern Categories](https://style.gallery/materials/v2/pages/patterns/index.md).
Next: [Layout Recipes](https://style.gallery/materials/v2/pages/recipes/index.md) for screen-level composition, or return to the [Layout Pattern Catalog](https://style.gallery/materials/v2/pages/CATALOG.md) when choosing another primitive.