2nd/10_Wiki/Topic_CSS/CSS_HSL.md

---
id: css-hsl-colors
title: "CSS HSL Colors"
category: "Frontend"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["HSL", "hsl()", "HSLA", "hsla()", "hue saturation lightness", "CSS HSL values"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.88
created_at: 2026-06-23
updated_at: 2026-06-23
review_reason: ""
merge_history: []
tags: ["css", "web", "frontend", "w3schools", "color", "hsl", "hsla"]
raw_sources: ["https://www.w3schools.com/css/css_colors_hsl.asp"]
applied_in: []
github_commit: ""
---

# [[CSS HSL Colors]]

## 🎯 한 줄 통찰 (One-line insight)
HSL specifies a color by hue, saturation, and lightness — `hsl(hue, saturation, lightness)` — and `hsla()` adds an alpha channel (0.0–1.0) for opacity. [S1]

## 🧠 핵심 개념 (Core concepts)
- **HSL = Hue, Saturation, Lightness.** [S1]
- **Syntax** — `hsl(hue, saturation, lightness)`. [S1]
- **Hue** — a degree on the color wheel from 0 to 360: 0 (or 360) is red, 120 is green, 240 is blue. [S1]
- **Saturation** — a percentage value: 0% means a shade of gray, and 100% is the full color. [S1]
- **Lightness** — a percentage: 0% is black, 50% is neither dark nor light, 100% is white. [S1]
- **HSLA** — extends HSL with an alpha channel for opacity: `hsla(hue, saturation, lightness, alpha)`, alpha 0.0 (transparent) to 1.0 (opaque). [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Saturation controls vividness** — lowering saturation toward 0% washes a color out toward gray while keeping hue and lightness fixed. [S1]
- **Lightness controls brightness** — sweeping lightness from 0% to 100% moves any hue from black through full color to white. [S1]
- **Gray via HSL** — set hue and saturation to 0 and vary only lightness to produce shades of gray. [S1]

## 📖 세부 내용 (Details)
**HSL Value**
HSL stands for hue, saturation, and lightness. An HSL color value is specified with `hsl(hue, saturation, lightness)`. Hue is a degree on the color wheel from 0 to 360, where 0 is red, 120 is green, and 240 is blue. Saturation is a percentage value: 0% means a shade of gray, and 100% is the full color. Lightness is also a percentage: 0% is black, 50% is neither dark nor light, and 100% is white. [S1]

**Saturation**
With hue at 0 (red) and lightness at 50%, varying the saturation demonstrates the effect: [S1]
```css
hsl(0, 100%, 50%)
hsl(0, 80%, 50%)
hsl(0, 60%, 50%)
hsl(0, 40%, 50%)
hsl(0, 20%, 50%)
hsl(0, 0%, 50%)
```

**Lightness**
With hue at 0 (red) and saturation at 100%, varying the lightness demonstrates the effect from no light (black) through full color to full lightness (white). The page shows this across lightness values ranging from 0% to 100%: [S1]
```css
hsl(0, 100%, 0%)    /* 0% = black */
hsl(0, 100%, 100%)  /* 100% = white */
```
(Intermediate lightness swatches appear on the page but their exact numeric values are: Not found in source.)

**Shades of Gray**
Shades of gray are often defined by setting the hue and saturation to 0 and adjusting the lightness from 0% (black) to 100% (white): [S1]
```css
hsl(0, 0%, 0%)    /* black */
hsl(0, 0%, 100%)  /* white */
```
(Intermediate gray lightness values between these endpoints are shown as swatches on the page but their exact numeric values are: Not found in source.)

**HSLA Value**
HSLA color values are an extension of HSL with an alpha channel, which specifies the opacity for a color. An HSLA color value is specified with `hsla(hue, saturation, lightness, alpha)`, where the alpha parameter is a number between 0.0 (fully transparent) and 1.0 (not transparent at all). [S1]

The page demonstrates the same color at increasing opacity: [S1]
```css
hsla(9, 100%, 64%, 0)
hsla(9, 100%, 64%, 0.2)
hsla(9, 100%, 64%, 0.4)
hsla(9, 100%, 64%, 0.6)
hsla(9, 100%, 64%, 0.8)
hsla(9, 100%, 64%, 1)
```

## 🛠️ 적용 사례 (Applied in summary)
The color values above are the page's own demonstration examples. No external project/commit applications found in the source.

## 💻 코드 패턴 (Code patterns)
HSL function (language: CSS):
```css
selector {
  color: hsl(hue, saturation, lightness); /* hue 0–360; sat/light 0%–100% */
}
```
HSLA function with opacity:
```css
selector {
  color: hsla(hue, saturation, lightness, alpha); /* alpha 0.0–1.0 */
}
```

## ⚖️ 비교 및 선택 기준 (Comparison & decision criteria)
- **HSL vs HSLA** — use `hsl()` for an opaque color described intuitively by hue/saturation/lightness; use `hsla()` when an opacity (alpha) value from 0.0 to 1.0 is also required. [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:** 0.88
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[CSS Tutorial]]
- **관련 개념:** [[CSS RGB]], [[CSS HEX]], [[CSS Colors]], [[CSS Background Color]]
- **참조 맥락:** Referenced whenever a color is described perceptually by hue, saturation, and lightness, or when an opacity channel is needed via HSLA.

## 📚 출처 (Sources)
- [S1] W3Schools — CSS HSL Colors — https://www.w3schools.com/css/css_colors_hsl.asp

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