Web crawling and web scraping sometimes go hand in hand. In other cases, they are independent of each other. Given the impact each of these processes has had on the internet ecosystem and businesses that operate both online and offline, understanding what each entails is vital. Here, we explore the definitions of web scraping and web scrapers as well as web crawling and web crawler with the aim of also establishing which came first.
Web scraping, also known as web data extraction or web harvesting, involves retrieving data from websites. It can be undertaken manually, as is the case with basic copy and pasting functions, or automatically using software and scripts collectively known as web scrapers.
As part of the web harvesting process, web scrapers identify the target sites through their Uniform Resource Locators (URLs), send HTTP requests, maintain user sessions, and download HTML code files sent by servers. Subsequently, the scrapers parse the data, the technical term for converting the code to a readable format, before storing it in a structured, downloadable format, such as .csv.
Some sophisticated, pre-built scrapers also choose the right proxy servers. Built to mimic human browsing behavior, they are also fitted with proxy rotators. In doing so, they circumvent anti-scraping techniques put in place to prevent data harvesting.
Web scrapers are preferred in large-scale data extraction exercises that involve tens or even hundreds of websites, which cumulatively have thousands of web pages. In such cases, web scrapers are used alongside web crawlers.
Web crawling is the process of scanning the internet for newly updated or uploaded web pages and content to create collections. The collections contain unique identifiers, known as indexes, that facilitate future references and retrieval when required.
Usually, bots, known as web crawlers, are responsible for scanning the internet and indexing web pages. When these bots crawl a website, they begin by accessing a single page before going through every link within that page upon performing a scan. Then, they repeat these steps for every webpage that makes up the website, all the while assigning the identifiers to each.
Web crawlers also index the type of data found on each web page. For instance, if you tried crawling an e-commerce website, the crawler would first go to the site’s homepage. Next, it follows the links on the homepage in a process that enables it to discover product pages. Finally, it indexes each page before finding the product data, including price, title, image, description, and reviews.
Web Crawling in Action
Notably, web crawling principally defines how search engines operate in part. Major search engines are known to be fast. In fact, some display the number of results identified in microseconds. Well, this speed is due to the fact that the search engine’s web crawlers have scoured the internet and identified multiple webpages that they then index for future reference. Thus, whenever you input a search term on the search bar, the search engine merely accesses already indexed information.
Web crawlers are also at the center of how job aggregator sites gather information about new openings. These sites rely on bots that scan websites. They discover career pages that advertise job openings by following the links therein.
Web Crawling vs. Web Scraping
For large-scale web scraping to be efficient and fast, it requires the services of web crawlers. First, the bots scan websites to identify the webpages that contain the requisite data. Then, web scrapers take over once the crawlers index the pages for future retrieval. They automatically extract data, which they then store in a structured format for download. This process explains how job aggregator sites populate their websites with job openings.
However, in some cases, these processes proceed independently of each other. For instance, whenever search engine bots scan the internet to identify new web content, they do not require the services of web scrapers. Similarly, small-scale data extraction from a handful of websites does not prompt the use of web crawlers.
That said, which came first? Web crawling or web scraping? Well, the answer depends on how you look at it. As stated, web scraping can either be manual or automated, with the manual approach relying on the copy and paste function. This function was invented in the 1970s by computer scientist Larry Tesler. Thus, it can be said to have come first as it even preceded the world wide web, which was invented in 1989.
Nonetheless, if you consider how search engines operate, web crawling comes first. For more information on crawling vs scraping you can read the article here.
The web crawling vs. web scraping conversation creates interesting discussion points. Key among them is which between the two came first. As detailed, this depends on your perspective. But, from a historical point of view, web scraping came first.