2nd/10_Wiki/Topic_CSS/CSS_Flexbox_Align.md

---
id: css-flexbox-align-items
title: "CSS Flexbox Align Items"
category: "Frontend"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["align-items", "align-content", "flexbox cross-axis alignment", "vertical flex alignment", "flexbox centering"]
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", "flexbox", "align-items", "align-content"]
raw_sources: ["https://www.w3schools.com/css/css3_flexbox_container_align.asp"]
applied_in: []
github_commit: ""
---

# [[CSS Flexbox Align Items]]

## 🎯 한 줄 통찰 (One-line insight)
`align-items` manages vertical alignment of flex items along the cross-axis, while `align-content` aligns wrapped flex lines; combining `justify-content: center` with `align-items: center` produces true centering. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`align-items` = cross-axis alignment** — controls vertical alignment of flex items along the cross-axis. [S1]
- **`align-content` = line alignment** — aligns the flex lines, and only has effect when flex items wrap onto multiple lines. [S1]
- **True centering** — set both `justify-content` and `align-items` to `center`. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Height is required to see effect** — the cross-axis examples set a `height` on the container so vertical alignment is observable. [S1]
- **`align-content` needs `flex-wrap: wrap`** — line alignment only matters once items wrap onto multiple lines. [S1]

## 📖 세부 내용 (Details)
**The align-items Property**
The `align-items` property manages vertical alignment of flex items along the cross-axis. Available values are `normal` (default), `stretch`, `center`, `flex-start`, `flex-end`, and `baseline`. [S1]

The `center` value aligns the flex items in the middle of the container. [S1]
```css
.flex-container {
  display: flex;
  height: 200px;
  align-items: center;
}
```

The `flex-start` value aligns the flex items at the top of the container. [S1]
```css
.flex-container {
  display: flex;
  height: 200px;
  align-items: flex-start;
}
```

The `flex-end` value aligns the flex items at the bottom of the container. [S1]
```css
.flex-container {
  display: flex;
  height: 200px;
  align-items: flex-end;
}
```

The `stretch` value stretches the flex items to fill the container (this is equal to `normal`, which is default). [S1]
```css
.flex-container {
  display: flex;
  height: 200px;
  align-items: stretch;
}
```

**The align-content Property**
The `align-content` property aligns the flex lines. It only has effect when flex items wrap onto multiple lines. Available values are `stretch` (default), `center`, `flex-start`, `flex-end`, `space-between`, `space-around`, and `space-evenly`. [S1]

With `center`, the flex lines are packed toward the center of the container. [S1]
```css
.flex-container {
  display: flex;
  height: 400px;
  flex-wrap: wrap;
  align-content: center;
}
```

With `space-between`, the space between the flex lines are equal. [S1]
```css
.flex-container {
  display: flex;
  height: 400px;
  flex-wrap: wrap;
  align-content: space-between;
}
```

**True Centering with Flexbox**
To achieve true centering, set both the `justify-content` and the `align-items` properties to `center`. [S1]
```css
.flex-container {
  display: flex;
  height: 400px;
  justify-content: center;
  align-items: center;
}
```

## 🛠️ 적용 사례 (Applied in summary)
The page's own examples apply each value to a `.flex-container` with a fixed `height`, plus a combined centering example. No external project/commit applications found in the source.

## 💻 코드 패턴 (Code patterns)
Center flex items on both axes (language: CSS):
```css
.flex-container {
  display: flex;
  height: 400px;
  justify-content: center;
  align-items: center;
}
```

## ⚖️ 비교 및 선택 기준 (Comparison & decision criteria)
- **`align-items`** — aligns individual flex items along the cross-axis; works on single-line layouts. [S1]
- **`align-content`** — aligns whole flex lines and only has effect when items wrap onto multiple lines (requires `flex-wrap: wrap`). [S1]

## ⚖️ 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 Flexbox Justify Content]], [[CSS Flex Items]], [[CSS Flexbox Responsive]]
- **참조 맥락:** Referenced whenever aligning flex items vertically (cross-axis) or centering content within a flex container.

## 📚 출처 (Sources)
- [S1] W3Schools — CSS Flexbox Align Items — https://www.w3schools.com/css/css3_flexbox_container_align.asp

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