What is Crawler?
A crawler is nothing but a computer program that automatically searches documents on the Web. Crawlers are primarily programmed for repetitive actions so that browsing is automated. Search engines use crawlers most frequently to browse the internet and build an index.
A crawler is a program that visits Web sites and reads their pages and other information in order to create entries for a search engine index. The major search engines on the Web all have such a program, which is also known as a “spider” or a “bot”. Crawlers are typically programmed to visit sites that have been submitted by their owners as new or updated. Entire sites or specific pages can be selectively visited and indexed. Crawlers apparently gained the name because they crawl through a site a page at a time, following the links to other pages on the site until all pages have been read.
Search engines don’t magically know what websites exist on the Internet. The programs have to crawl and index them before they can deliver the right pages for keywords and phrases, or the words people use to find a useful page.
For Example:
Think of it like cloth shopping in a new store. You have to walk down the aisles and look at the products before you can pick out what you need. In the same way, search engines use web crawler programs as their helpers to browse the Internet for pages before storing that page data to use in future searches.
Why Crawling is important for any Website.
If the crawler doesn’t crawl a website, then it can’t be indexed, and it won’t show up in search results. For this reason, if a website owner wants to get organic traffic from search results, it is very important that they don’t block web crawler bots. Crawler updating your website content for search indexing so that a website shows up higher in search engine results.
How long will it take a crawler to index our new pages Or website?
It has many factors but the major one is the website’s popularity, crawlability, and structure all factor into how long it will take Google to index a site. In general, Googlebot will find its way to a new website between four days and four weeks. However, this is a projection and some users have claimed to be indexed in less than a day.
Roadblocks for web crawlers
There are a few ways to block web crawlers from accessing your pages purposefully. Not every page on your site should rank in the SERPs, and these crawler roadblocks can protect sensitive, redundant, or irrelevant pages from appearing for keywords.
The first roadblock is the noindex meta tag, which stops search engines from indexing and ranking a particular page. It’s usually wise to apply noindex to admin pages, thank you pages, and internal search results.
Another crawler roadblock is the robots.txt file. This directive isn’t as definitive because crawlers can opt-out of obeying your robots.txt files, but it’s handy for controlling your crawl budget.
Below are some web crawlers active on the Internet.
Google : Googlebot
Bing : Bingbot
Yandex : Yandex Bot
Baidu : Baidu Spider
Yahoo : Slurp Bot
DuckDuckGo : DuckDuckBot
Facebook: Facebot ( which is designed to help improve advertising performance. )
Sogou Spider
Exabot
Alexa crawler
