# a11y.css accessibility checker

> a11y.css provides warnings about possible risks and mistakes that exist in HTML code through a style sheet. This extension also provides several accessibility-related utilities. see https://github.com/ffoodd/a11y.css/tree/webextension for details

Canonical page: [https://chrome-stats.com/d/a11ycss](https://chrome-stats.com/d/a11ycss)

## Overview

- **ID:** `a11ycss`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** Stephane Deschamps
- **Category:** web-development,other
- **Daily users:** 181
- **Weekly downloads:** 2
- **Rating:** 5.00 / 5 (1 ratings)
- **Version:** 2.1.0
- **Last updated:** 2024-12-10
- **First published:** 2018-01-18
- **Size:** 679 KB
- **Data as of:** 2026-09-05
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/a11ycss/)
- **Website:** [https://ffoodd.github.io/a11y.css](https://ffoodd.github.io/a11y.css)

## Description

**a11y.css accessibility checker** is a Chrome extension designed to help developers identify potential accessibility issues in HTML code by injecting a specialized CSS stylesheet. It highlights possible risks and common mistakes directly on web pages, enabling a quick assessment of a site's accessibility quality.

Beyond its core warning functionalities, the extension includes useful utilities such as outlining keyboard navigation focus, displaying detected languages based on `lang` attributes, and checking `alt` and `title` attributes on images. This makes it an essential tool for improving web accessibility and ensuring inclusive design.

Originally a bookmarklet by Gaël Poupard, the extension was developed by Stéphane Deschamps with contributions from accessibility experts. It's open for community feedback and bug reports on GitHub.

## Rankings

- #8,671 — Overall
- #81 — visibility
- #121 — free access

## Permissions and access

### Permissions

- `activeTab`
- `storage`
- `scripting`
- `tabs`

### Content script matches

- `*`

## Safety

- **Risk impact:** High risk impact
- **Risk likelihood:** Low risk likelihood

### Analysis details

- Grants access to browser tabs, which can be used to track user browsing habits and history, presenting a privacy concern.
- This extension has low user count. Unpopular extensions may not be stable or safe.

> Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing).

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Source: [Chrome-Stats](https://chrome-stats.com/d/a11ycss)