What Is a Crawler?
A crawler is a special computer program used by search engines to visit web pages on the internet. It looks at the content of each page and sends what it finds back to the search engine so pages can appear in search results.
Definition
A crawler, also called a web crawler, bot, or spider, is software that:
- Goes from one web page to another by following links
- Reads text, links, and some code on each page
- Sends this data to the search engine to store in its index
Googlebot is an example of a well known crawler used by Google.
Why Crawler Matters
If crawlers cannot reach or read your website, your pages will not show in search results. A crawler matters because it is the first step in:
- Discovering new pages on your site
- Updating changed pages so search results stay fresh
- Helping the search engine understand what your pages are about
Good technical SEO makes it easier and faster for crawlers to move through your site.
How Crawler Works
Most crawlers follow a simple process:
- Start list The crawler begins with a list of known URLs, for example from sitemaps or older crawls.
- Visit a page It requests the page from the web server, like a normal visitor would.
- Check rules It looks at the
robots.txtfile and meta tags to see what is allowed or blocked. - Read content It scans text, title, headings, links, and some code parts.
- Follow links It adds new links it finds to its list of pages to visit next.
- Send data It sends what it found back to the search engine index so the page can be ranked later.
Crawler vs Related Terms
- Crawler vs bot A crawler is a type of bot. Bot is a broad word for any automated program. A crawler is a bot made for scanning web pages.
- Crawler vs indexer The crawler collects page data. The indexer is the system that stores and organizes that data to use in search results.
- Crawler vs spider Spider is another common name for a crawler. In most cases they mean the same thing.
Example of Crawler
Imagine you publish a new blog post on your site. Here is what happens with a crawler:
- You add the post to your sitemap and link to it from your homepage.
- Googlebot visits your homepage and sees the new link.
- Googlebot follows the link, reads the new post, and sends the content to Google.
- Google adds the post to its index, and after some time the post can show up in Google search results.
FAQs
Is a crawler the same as Googlebot?
Googlebot is one specific crawler used by Google. Other search engines have their own crawlers, such as Bingbot for Bing.
How often do crawlers visit my site?
It depends on how important and how active your site is. Popular and often updated sites may get crawled many times a day. Small or rarely updated sites may be crawled less often.
How can I help crawlers crawl my site?
You can help by using a clear site structure, internal links, clean URLs, an XML sitemap, fast loading pages, and by avoiding blocking important pages in robots.txt or with noindex tags.
Can I block a crawler?
Yes. You can ask crawlers not to visit or not to index certain pages using the robots.txt file and meta robots tags. But if you block crawling of a page, that page usually cannot appear in search results.
