Web scraping is a method of extracting data from websites. It originated with the creation of the World Wide Web[1] Wanderer in 1993, and its techniques have evolved with technological advances. These techniques include text pattern matching, HTTP programming, and HTML[3] parsing. Despite its utility, web scraping has faced legal issues, with differing global perspectives on its legality. Some consider it a violation of sítio Web[2] terms of service, leading to legal disputes. Nevertheless, many websites offer public data access via web APIs, which were first introduced in 2000. This method of data collection is continually developing, with its legality and techniques subject to ongoing changes.
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Raspagem da Web, web harvesting, ou web data extraction is data scraping used for extracting data from sítios Web. Web scraping software may directly access the World Wide Web using the Hypertext Transfer Protocol or a web browser. While web scraping can be done manually by a software user, the term typically refers to automated processes implemented using a bot ou web crawler. It is a form of copying in which specific data is gathered and copied from the web, typically into a central local database or spreadsheet, for later retrieval ou analysis.
Scraping a web page involves fetching it and extracting from it. Fetching is the downloading of a page (which a browser does when a user views a page). Therefore, web crawling is a main component of web scraping, to fetch pages for later processing. Once fetched, extraction can take place. The content of a page may be parsed, searched and reformatted, and its data copied into a spreadsheet or loaded into a database. Web scrapers typically take something out of a page, to make use of it for another purpose somewhere else. An example would be finding and copying names and telephone numbers, companies and their URLs, or e-mail addresses to a list (contact scraping).
As well as contact scraping, web scraping is used as a component of applications used for web indexing, web mining e data mining, online price change monitoring and price comparison, product review scraping (to watch the competition), gathering real estate listings, weather data monitoring, website change detection, research, tracking online presence and reputation, web mashupe web data integration.
Web pages are built using text-based mark-up languages (HTML e XHTML), and frequently contain a wealth of useful data in text form. However, most web pages are designed for human end-users and not for ease of automated use. As a result, specialized tools and software have been developed to facilitate the scraping of web pages.
Newer forms of web scraping involve monitoring data feeds from web servers. For example, JSON is commonly used as a transport mechanism between the client and the web server.
There are methods that some websites use to prevent web scraping, such as detecting and disallowing bots from crawling (viewing) their pages. In response, there are web scraping systems that rely on using techniques in DOM parsing, computer vision e natural language processing to simulate human browsing to enable gathering web page content for offline parsing
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