Google uses sophisticated algorithms for determining how often to crawl your site. Their goal is to crawl as many pages as possible from your site on each visit without overwhelming your server's bandwidth.
Too many requests on your site in a very short period can cause your site to load slowly and even cause load issues on the server. This is especially true of very busy websites, or websites that are poorly or inefficiently coded. If you are experiencing bandwidth related server load issues (i.e. too many requests too quickly), you may want to reduce Google's crawl rate (the time used by Googlebot to crawl your website for an entire domain or subdomain).
Changing Google's Crawl Rate
Google allows you to adjust the crawl rate, but you cannot specify different crawl rates for sections of your site such as specific folders or subdirectories. For example, you can specify a custom crawl rate for www.yoursitesdomain.com and subdomain.yoursitesdomain.com, but you cannot specify a custom crawl rate for www.yoursitesdomain.com/subfolder.
Changing Google's crawl rate only changes the speed of Googlebot's requests during the crawl process. It does not have any effect on how often Google crawls your site or how deeply the URL structure is crawled. To change Google's crawl rate on your website:
- Log into Google Webmaster Tools.
- If you have not already done so, add your site to Google Webmaster Tools.
- On the Webmaster Tools home page, click on the site for which you'd like to adjust the crawl rate.
- Click on the gear icon in the upper-right corner of the page, and select Site Settings from the drop-down menu.
- In the Crawl rate section, select the option you prefer, and then click Save.
The new crawl rate will be valid for only 90 days.