---
id: css-pseudo-elements
title: "CSS Pseudo-elements"
category: "Frontend"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["pseudo-elements", "::before", "::after", "::first-line", "::marker", "double-colon selectors"]
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", "pseudo-elements", "selectors"]
raw_sources: ["https://www.w3schools.com/css/css_pseudo_elements.asp"]
applied_in: []
github_commit: ""
---

# [[CSS Pseudo-elements]]

## 🎯 한 줄 통찰 (One-line insight)
A CSS pseudo-element is a keyword added to a selector that lets you style a specific part of an element — the first line, the first letter, inserted content, list markers, selected text, or a dialog backdrop. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Definition** — A CSS pseudo-element is a keyword that can be added to a selector, to style a specific part of an element. [S1]
- **Double-colon syntax** — pseudo-elements are written with `::` after the selector. [S1]
- **Two families** — text pseudo-elements (`::first-line`, `::first-letter`) and content pseudo-elements (`::before`, `::after`, `::marker`, `::selection`, `::backdrop`). [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Style a part, not the whole** — pseudo-elements address sub-parts of an element (a line, a letter, generated content) rather than the element as a whole. [S1]
- **Syntax pattern** — `selector::pseudo-element-name { CSS properties }`. [S1]

## 📖 세부 내용 (Details)
**Definition** [S1]
A CSS pseudo-element is a keyword that can be added to a selector, to style a specific part of an element. Common uses include:
- Styling the first letter or first line of an element
- Inserting content before or after an element
- Styling list item markers
- Styling user-selected portions of an element
- Styling the viewbox behind a dialog box

**Syntax** [S1]
```css
selector::pseudo-element-name {
  CSS properties
}
```

**Text pseudo-elements** [S1]

| Pseudo-element | Description |
| --- | --- |
| `::first-line` | Style the first line of text |
| `::first-letter` | Style the first letter of text |

**Content pseudo-elements** [S1]

| Pseudo-element | Description |
| --- | --- |
| `::before` | Insert content before an element |
| `::after` | Insert content after an element |
| `::marker` | Style list item markers |
| `::selection` | Style user-selected text |
| `::backdrop` | Style dialog backdrop |

The source references a complete CSS Pseudo-elements Reference for the full list. [S1]

## 🛠️ 적용 사례 (Applied in summary)
This page is an overview/index; the detailed applied examples live on the dedicated text and content pseudo-element pages. No external project/commit applications found in the source.

## 💻 코드 패턴 (Code patterns)
Pseudo-element syntax (language: CSS):
```css
selector::pseudo-element-name {
  CSS properties
}
```

## ⚖️ 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 Text Pseudo-elements]], [[CSS Content Pseudo-elements]], [[CSS Structural Pseudo-classes]]
- **참조 맥락:** The entry point whenever styling a specific part of an element rather than the whole.

## 📚 출처 (Sources)
- [S1] W3Schools — CSS Pseudo-elements — https://www.w3schools.com/css/css_pseudo_elements.asp

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