By Shad Super in Questions —

How Can I Specify Crawl-Delay in the robots.txt File, and What Are the Implications of Using This Directive for Different Search Engines?

Summary

The crawl-delay directive in the robots.txt file is used to specify the number of seconds a search engine should wait before crawling consecutive pages from the same site. Implementing this directive helps manage server load and prevents overloading your server with too many requests in a short period. However, its support varies across different search engines, and it should be used judiciously.

Understanding Crawl-Delay

Definition

The crawl-delay directive in the robots.txt file instructs search engine crawlers to wait a specific number of seconds before retrieving the next page. This can help prevent your server from becoming overwhelmed by too many requests in a short time.

Example of Syntax

Including the crawl-delay directive in your robots.txt file can be as simple as the following:

<code>
User-agent: *
Crawl-delay: 10
</code>

In this example, the directive tells all search engine bots to wait 10 seconds between each request.

Implications for Different Search Engines

Google

Googlebot does not support the crawl-delay directive in the robots.txt file. Instead, you need to adjust Google's crawl rate through the Google Search Console. More details can be found in the official documentation [Google Search Console Help, 2023].

Bing

Bingbot does support the crawl-delay directive. Including the directive in your robots.txt file, as shown in the example above, can effectively control the crawling rate of Bingbot. More information is provided by Microsoft [Robots.txt, 2023].

Yahoo

Yahoo's Slurp bot, which is powered by Bing, also adheres to the crawl-delay directive. Thus, defining a crawl delay for Bing will similarly affect Yahoo's Slurp bot.

Yandex

YandexBot supports the crawl-delay directive, and you can specify the delay in seconds in your robots.txt file. Additional information can be found on the Yandex Webmaster help page [Yandex Webmaster, 2023].

Baidu

BaiduBot currently supports the crawl-delay directive. Information regarding Baidu's bot behavior is available in their webmaster documentation [Baidu Webmaster, 2023].

Best Practices for Using Crawl-Delay

Assess Your Server’s Capacity

Before setting a crawl delay, it is essential to understand your server's load capacity. Use server monitoring tools to assess how much load your server can handle without performance degradation.

Test and Adjust Crawl-Delay

Start with a reasonable crawl delay and monitor your server logs to observe its effects. Adjust the crawl delay as needed based on your server's performance and the behavior of different search engine bots.

Communicate with Search Engines

If you observe frequent crawling issues or spikes in server load, reach out to search engines via their webmaster tools for more precise control over crawling behavior. For example, use Google Search Console to adjust Google's crawl rate.

Conclusion

The crawl-delay directive is a valuable tool for managing how frequently search engine bots crawl your site. While not universally supported across all search engines, it has specific use cases for those that do support it. As with all directives in the robots.txt file, its proper implementation requires careful planning and monitoring to ensure optimal site performance and availability.

References