What web scraping techniques are known nowadays?

Web scraping is an area with active development and human-computer interaction. Web scraping requires the development of artificial intelligence in the processing and understanding of the text of online pages. Modern scraping solutions range from special, labor-intensive, to fully automated systems that can transform entire websites into structured information in a specific format.

This post will describe current methods of collecting information from the Internet.

By the way, the history of web scraping is actually much longer than it seems, it begins from the time the Internet appeared.

"Copy-paste" manually

Sometimes even the best web scraping technology cannot replace a person’s manual work when a user copies and pastes text. In some cases, this is the only workable solution, for example, when websites set barriers to web scraping programs and block automated copying of text.

Matching text patterns

A simple but powerful approach to extracting web page information can be based on the UNIX grep command or regular expression matching tools of programming languages ​​(such as Perl or Python).

HTTP Programming

Static and dynamic web pages can be obtained by sending HTTP requests to a remote web server using socket programming.

HTML parsing

Many web sites consist of a large number of pages generated dynamically from the main structured source - the database. Data from the same category is usually encoded into similar pages using a common script or template. In data mining, a program that detects such patterns in a specific source of information, extracts its contents and translates it into a form/shell. Analyzed pages can be easily identified in terms of a common URL scheme. In addition, some semi-structured data query languages, such as XQuery and HTQL, can be used to parse HTML pages and extract and transform page content.

Document Object Model

DOM - a program with an API for HTML and XML documents.

By embedding a full-fledged web browser, such as Internet Explorer or a Mozilla browser control, programs can extract dynamic content created by client-side scripts. These browser controls analyze web pages in the DOM to extract part of the pages.

Vertical aggregation

There are several companies that have developed vertical special platforms that create and control many bots. Bots work without direct human involvement and at the same time, their interaction with users occurs without communication with the target site. Preparation involves creating a knowledge base for the entire vertical, and then the platform automatically creates bots. The reliability of the platform is measured by the quality of the information received (usually the number of fields) and its scalability (up to hundreds or thousands of sites). This scalability is mainly used to target long tail sites that conventional aggregators find difficult or too time consuming to collect content.

So, web scraping programs are not designed for ordinary users, programmers work with them, who in most cases write codes for specific tasks. Therefore, if you want to get high-quality data from web resources, it is much easier to turn to special services, such as Scraper.