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Alt-Text Scan Tool

A Python script for scanning websites to evaluate the quality of alt text in images and generate actionable accessibility suggestions.

Overview

This tool crawls websites or parses their sitemap to collect images and analyze their alt attributes for accessibility compliance. It generates a CSV file summarizing issues, suggestions, and metadata for each image.

Features

  • Crawl Websites: Analyze images from websites either by crawling pages directly or parsing their sitemap.
  • Accessibility Checks: Detect missing, meaningless, or excessively long alt text.
  • Readability Analysis: Assess readability for alt text over 25 characters.
  • Rate Limiting: Throttle requests to avoid overloading servers.
  • CSV Reports: Save analysis results to a CSV file.
  • New Features:
    • Added support for crawling without relying on sitemap.xml using the --crawl_only option.
    • Readability analysis is now performed only on alt text longer than 25 characters.
    • Improved handling of nested sitemaps with recursive parsing.
    • Enhanced suggestions for WCAG compliance, including identifying decorative images and overly verbose alt text.

Installation

Prerequisites

  1. Python 3.10 or later.

  2. Install the required Python libraries:

    pip install -r requirements.txt

    Required Libraries:

    • requests
    • bs4 (BeautifulSoup)
    • pandas
    • tqdm
    • textstat
    • textblob

Usage

Command-Line Arguments

Argument Description
domain The base domain to analyze (e.g., https://example.com).
--sample_size Number of URLs to sample from the sitemap (default: 100).
--throttle Throttle delay in seconds between requests (default: 1).
--crawl_only Skip sitemap parsing and start crawling directly (default: False).

Examples

1. Analyze a Site Using the Sitemap

python alt_text_scan.py https://example.com --sample_size 200 --throttle 2

This will:

  • Parse https://example.com/sitemap.xml to find URLs.
  • Sample up to 200 URLs for analysis.
  • Throttle requests with a 2-second delay.

2. Crawl a Site Directly

python alt_text_scan.py https://example.com --sample_size 200 --throttle 2 --crawl_only

This will:

  • Bypass sitemap.xml.
  • Crawl the site starting from the homepage.
  • Analyze up to 200 pages.

Output

The script generates a CSV file named after the domain being analyzed, e.g., example.com_images.csv. Each row corresponds to an image and contains:

Column Description
Image_url The URL of the image.
Alt_text The alt attribute of the image (if available).
Title The title attribute of the image (if available).
Count The number of times the image appears.
Source_URLs Pages where the image was found.
Size (KB) The size of the image in kilobytes.
Suggestions Recommendations for improving the alt text based on WCAG standards.

Key Accessibility Checks

  1. Missing or Empty alt Text:

    • Detects images with no alt attribute or empty alt values.
    • Suggests adding meaningful descriptions.

  2. Readability Analysis:

    • Evaluates readability for alt text over 25 characters.
    • Suggests simplifying overly complex text.

  3. Text Length:

    • Flags alt text under 25 characters as too short.
    • Flags alt text over 250 characters as too verbose.

  4. Meaningless alt Text:

    • Identifies generic or placeholder alt text (e.g., "image of", "placeholder").

  5. Large Image Files:

    • Highlights images over 250 KB as candidates for optimization.

Known Limitations

  1. 403 Forbidden Errors: Some servers may block automated requests. Use --throttle to reduce request frequency or adjust headers in the script.
  2. Large Sitemaps: Parsing deeply nested sitemaps may exceed the recursion depth limit. Use the --crawl_only option if necessary.
  3. CAPTCHA Restrictions: Servers using CAPTCHAs or aggressive rate-limiting may block requests.

Contributing

Contributions are welcome! Please open an issue or submit a pull request on GitHub.

License

This project is licensed under the MIT License.