---
id: css-supports
title: "CSS @supports"
category: "Frontend"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["@supports", "feature queries", "CSS feature query", "supports rule", "progressive enhancement CSS", "browser feature detection CSS"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.89
created_at: 2026-06-23
updated_at: 2026-06-23
review_reason: ""
merge_history: []
tags: ["css", "web", "frontend", "w3schools", "at-rule", "progressive-enhancement"]
raw_sources: ["https://www.w3schools.com/css/css_supports_rule.asp"]
applied_in: []
github_commit: ""
---

# [[CSS @supports]]

## 🎯 한 줄 통찰 (One-line insight)
The `@supports` rule (a feature query) checks whether the browser supports a specific CSS property or value and applies styles only when it does, letting you define fallbacks for unsupported features. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`@supports` rule** — lets you check if the browser supports a specific CSS property or value, and define fallback styles if the feature is not supported. [S1]
- **Conditional application** — useful for applying styles only when the browser can handle them. [S1]
- **Operators** — you can use `and`, `or`, and `not` for multiple conditions. [S1]
- **Negation** — `not` applies styles only when a feature is not supported. [S1]
- **Fallback rule (Note)** — always provide fallback styles outside of `@supports`, for older browsers. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Test then enhance** — write base/fallback styles normally, then wrap the enhanced styles in `@supports (property: value) { ... }`. [S1]
- **Combine conditions** — chain feature tests with `and`/`or` (e.g. `(display: grid) and (gap: 10px)`). [S1]
- **Negative guard** — use `@supports not (...)` to style a warning or fallback path when a feature is absent. [S1]

## 📖 세부 내용 (Details)
The `@supports` rule lets you check if the browser supports a specific CSS property or value, and to define fallback styles if the feature is not supported. This is useful for applying styles only when the browser can handle them. [S1]

**Basic syntax** [S1]
```css
@supports (property: value) {
  /* CSS rules to apply if condition is true */
}
```

**Example — flex fallback** [S1]
```css
/* use this CSS if the browser does not support display: flex */
.container {
  float: left;
  width: 100%;
}

/* use this CSS if the browser supports display: flex */
@supports (display: flex) {
  .container {
    display: flex;
  }
}
```

**Example — grid fallback** [S1]
```css
/* use this CSS if the browser does not support display: grid */
.container {
  display: table;
  width: 90%;
  background-color: #2196F3;
  padding: 10px;
}

/* use this CSS if the browser supports display: grid */
@supports (display: grid) {
  .container {
    display: grid;
    grid: auto;
    grid-gap: 10px;
    background-color: #2196F3;
    padding: 10px;
  }
}
```

**Negating with `not`** — you can use `not` to apply styles only when a feature is not supported: [S1]
```css
@supports not (display: grid) {
  .warning {
    background-color: pink;
    padding: 10px;
    border: 1px solid red;
  }
}
```

**Combining conditions** — you can use `and`, `or`, and `not` for multiple conditions: [S1]
```css
@supports (display: grid) and (gap: 10px) {
  .container {
    display: grid;
    gap: 10px;
  }
}
```

**Note:** Always provide fallback styles outside of `@supports`, for older browsers. [S1]

**Reference table** [S1]

| At-rule | Description |
|---------|-------------|
| `@supports` | Used to test whether a browser supports a CSS feature |

## 🛠️ 적용 사례 (Applied in summary)
The page's applied cases are progressive-enhancement layouts: a float fallback enhanced to flex, a table fallback enhanced to grid, a `not`-guarded warning box, and a combined `(display: grid) and (gap: 10px)` query. No external project/commit applications found in the source.

## 💻 코드 패턴 (Code patterns)
Feature query with fallback (language: CSS):
```css
.container {
  float: left;
  width: 100%;
}

@supports (display: flex) {
  .container {
    display: flex;
  }
}
```
Negative feature query:
```css
@supports not (display: grid) {
  .warning {
    background-color: pink;
    padding: 10px;
    border: 1px solid red;
  }
}
```
Combined conditions:
```css
@supports (display: grid) and (gap: 10px) {
  .container {
    display: grid;
    gap: 10px;
  }
}
```

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
No contradictions found in the source.

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.89
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[CSS Tutorial]]
- **관련 개념:** [[CSS Grid 12-column Layout]], [[CSS RWD Intro]], [[CSS Grid Align]]
- **참조 맥락:** Browser feature detection for safely adopting newer CSS layout features with fallbacks.

## 📚 출처 (Sources)
- [S1] W3Schools — CSS @supports — https://www.w3schools.com/css/css_supports_rule.asp

## 📝 변경 이력 (Change history)
- 2026-06-23: Initial draft synthesized from the W3Schools "CSS @supports" page (Astra wiki-curation, P-Reinforce v3.1 format).