What is Screaming Frog SEO Spider?

Screaming Frog SEO Spider is a professional website crawler developed and maintained by Screaming Frog Ltd, a UK-based SEO agency. It's a desktop application available for Windows, macOS, and Linux that functions as a technical SEO audit tool. The software crawls websites like search engine bots do, following links and collecting data about page elements, errors, and SEO-related issues.

The tool identifies itself in server logs with the user agent string Screaming Frog SEO Spider/[version number] when using its default settings, though users can configure it to use different user agents including those of major search engines.

A distinctive characteristic of Screaming Frog SEO Spider is its hybrid storage engine that allows it to crawl both small and very large websites efficiently by saving data in RAM and on disk. By default, it crawls the raw HTML of websites using a breadth-first algorithm, but it can also render JavaScript-heavy pages using headless Chromium to discover content that requires JavaScript execution.

Why is Screaming Frog SEO Spider crawling my site?

If you're seeing Screaming Frog SEO Spider in your logs, it means someone (likely an SEO professional, digital marketer, or web developer) is analyzing your website for technical issues or opportunities. The crawler is typically used by:

Your own marketing team or SEO agency conducting a site audit
A potential business partner evaluating your site's technical health
A competitor researching your site structure and SEO elements

The crawler typically looks for broken links, redirect chains, meta data issues, duplicate content, structured data, and other technical SEO elements. The frequency of visits depends entirely on the user running the software, not on automated schedules. Each crawl is manually initiated by someone using the desktop application, and the depth and scope of the crawl are configured by that user.

Importantly, Screaming Frog SEO Spider is a commercial tool used by individuals and companies, not a service that automatically crawls the web. Each crawl is purposeful and directed.

What is the purpose of Screaming Frog SEO Spider?

Screaming Frog SEO Spider helps SEO professionals, webmasters, and digital marketers identify technical issues that could impact search engine rankings and user experience. The tool collects comprehensive data about a website's structure and content, allowing users to:

Find broken links and server errors
Analyze page titles, meta descriptions, and headings
Discover duplicate content
Audit redirects and identify redirect chains
Review robots directives and canonical tags
Generate XML sitemaps
Extract custom data using XPath, CSS selectors, or regex
Analyze site architecture and internal linking
Validate structured data
Check for spelling and grammar issues

The collected data is used to make informed decisions about technical SEO improvements. For website owners, having your site crawled by Screaming Frog can be beneficial as it often leads to improvements in your site's performance in search engines and better user experience.

How do I block Screaming Frog SEO Spider?

Screaming Frog SEO Spider respects robots.txt directives by default, though users can configure the tool to ignore these restrictions. To block the crawler, add the following to your robots.txt file:

User-agent: Screaming Frog SEO Spider
Disallow: /

This directs the crawler not to access any part of your site. If you want to block specific sections while allowing access to others, you can specify particular directories:

User-agent: Screaming Frog SEO Spider
Disallow: /private/
Disallow: /members/
Allow: /

Keep in mind that since Screaming Frog is a desktop application used by individuals, blocking it in robots.txt only prevents those who choose to respect your directives. Users can configure the tool to ignore robots.txt or use a different user agent.

If you need more definitive blocking, you might need to implement IP blocking at the server level, though this is challenging since the crawler could come from many different IP addresses depending on who's using it.

Blocking Screaming Frog might prevent beneficial technical analysis of your site, potentially leaving SEO issues undiscovered. In most cases, crawls from this tool are legitimate attempts to improve a website's performance rather than malicious activity.

Screaming Frog SEO Spider