跳到主要内容
哒哒星球DADA PLANET

Skill · 已公开版本

alt-text · 图片alt文本编写与审查指南

指导为图片编写有意义的alt文本,区分信息图、装饰图、链接图与文字图,含检查项与修复示例。

先看看示例

作者提供的示例,实际效果取决于你的输入和使用工具。

输入

审查官网首页图片,为装饰性背景图设空alt,为链接图标改为描述跳转目标。

输出

预期交付:按图片角色修正后的alt属性及审查清单(编辑说明,非实际运行结果)

方法说明

---
name: alt-text
description: "Use when reviewing image assets, markup, and CDN or build transforms related to Provide meaningful alt text for images. Check encoded size, rendered size, loading strategy, and above-the-fold impact together."
metadata:
  category: images
  priority: critical
  difficulty: beginner
  estimatedTime: "15"
  source: frontendchecklist.io
  url: https://frontendchecklist.io/rules/images/alt-text
---

# Provide meaningful alt text for images

Approximately 2.2 billion people worldwide have vision impairment. Screen readers read the alt attribute aloud—without meaningful alt text, users who are blind receive no information about image content. Missing alt text also fails WCAG 2.1 Success Criterion 1.1.1, which is a Level A (minimum) requirement. Search engines also rely on alt text to index image content.

## Quick Reference

- Every `<img>` must have an `alt` attribute—omitting it entirely violates WCAG 2.1 SC 1.1.1
- Decorative images use `alt=""` so screen readers ignore them
- Alt text should describe the image's *purpose*, not just its appearance
- Linked images: alt describes the link destination, not the visual

## Check

Scan all <img> elements in the codebase. Verify: 1) Every <img> has an alt attribute (missing alt is an error). 2) Decorative images use alt="". 3) Informative images have descriptive text that conveys the image's meaning—not just its file name. 4) Images that are links describe the destination. 5) Images of text reproduce the text in alt. Flag any <img> without alt, with alt matching the filename (e.g., alt="photo1.jpg"), or with generic values like alt="image" or alt="photo".

## Fix

For each image missing or with poor alt text: 1) Informative images—describe what the image conveys, not just what it shows (e.g., alt="Bar chart showing 40% increase in sales Q3 2024" not alt="chart"). 2) Decorative images—add alt="" so screen readers skip them. 3) Linked images—describe the link destination (e.g., alt="Visit our Twitter profile"). 4) Images of text—copy the text verbatim into alt. 5) Complex images (charts, infographics)—provide a short alt plus a longer description via aria-describedby or a visible caption.

## Explain

Explain WCAG 2.1 Success Criterion 1.1.1 Non-text Content: every image must have a text alternative. Screen readers announce the alt attribute aloud—without it, users who are blind or have low vision cannot understand the page. Bad alt text (like alt="image") is no better than no alt text. Decorative images must use alt="" explicitly so screen readers skip them entirely—omitting alt causes some screen readers to announce the filename.

## Code Review

Review image assets, markup, and delivery configuration related to Provide meaningful alt text for images. Flag exact files or components where format choice, sizing, or loading behavior violates the rule, and describe how to confirm the fix in DevTools.

---

For full implementation details, code examples, and framework-specific guidance,
see `references/rule.md`.

Rule page: https://frontendchecklist.io/rules/images/alt-text