Web scraping (also called web harvesting or web data extraction) is a computer software technique of extracting information from websites. Usually, such software programs simulate human exploration of the World Wide Web by either implementing low-level Hypertext Transfer Protocol (HTTP), or embedding a fully-fledged web browser, such as Internet Explorer or Mozilla Firefox.
Web scraping is closely related to web indexing, which indexes information on the web using a bot and is a universal technique adopted by most search engines. In contrast, web scraping focuses more on the transformation of unstructured data on the web, typically in HTML format, into structured data that can be stored and analyzed in a central local database or spreadsheet. Web scraping is also related to web automation, which simulates human browsing using computer software. Uses of web scraping include online price comparison, weather data monitoring, website change detection, research, web mashup and web data integration.
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Web scraping is the process of automatically collecting information from the world wide web. It is a field with active developments sharing a common goal with the semantic web vision, an ambitious initiative that still requires breakthroughs in text processing, semantic understanding, artificial intelligence and human-computer interactions. Web scraping, instead, favors practical solutions based on existing technologies that are often entirely ad hoc. Therefore, there are different levels of automation that existing web-scraping technologies can provide:
Web scraping may be against the terms of use of some websites. The enforceability of these terms is unclear.[2] While outright duplication of original expression will in many cases be illegal, in the United States the courts ruled in Feist Publications v. Rural Telephone Service that duplication of facts is allowable. U.S. courts have acknowledged that users of "scrapers" or "robots" may be held liable for committing trespass to chattels,[3][4] which involves a computer system itself being considered personal property upon which the user of a scraper is trespassing. The best known of these cases, eBay v. Bidder's Edge, resulted in an injunction ordering Bidder's Edge to stop data mining from the eBay web site. This case involved automatic placing of bids, known as auction sniping. However, in order to succeed on a claim of trespass to chattels, the plaintiff must demonstrate that the defendant intentionally and without authorization interfered with the plaintiff's possessory interest in the computer system and that the defendant's unauthorized use caused damage to the plaintiff. Not all cases of web spidering brought before the courts have been considered trespass to chattels.[5]
One of the first major tests of screen scraping involved American Airlines, and a firm called FareChase.[6] AA successfully obtained an injunction from a Texas trial court, stopping FareChase from selling software that enables users to compare online fares if it also searches AA's website. The airline argued that FareChase's websearch software trespassed on AA's servers when it collected the publicly available data. The injunction was appealed in 2003.
Southwest Airlines has also challenged screen-scraping practices, and has involved both FareChase and another firm, Outtask, in a legal claim. Southwest Airlines charged that the screen-scraping is Illegal since it is an example of "Computer Fraud and Abuse" and has led to "Damage and Loss" and "Unauthorized Access" of Southwest's site. It also constitutes "Interference with Business Relations", "Trespass" and "Harmful Access by Computer". They also claimed that screen-scraping constitutes what is legally known as Misappropriation and Unjust Enrichment, and is also a breach of the website's user agreement. Outtask denied all these claims, and claimed that the prevailing law in this case should be US Copyright law, and that under copyright, the pieces of information being scraped would not be subject to copyright protection. Although the cases were never resolved in the Supreme Court of the United States, FareChase was eventually shuttered by parent company Yahoo! and Outtask was purchased by travel expense company Concur[7].
Although these are early scraping decisions, and the theories of liability are not uniform, it is difficult to ignore a pattern emerging that the courts are prepared to protect proprietary content on commercial sites from uses which are undesirable to the owners of such sites. However, the degree of protection for such content is not settled, and will depend on the type of access made by the scraper, the amount of information accessed and copied, the degree to which the access adversely affects the site owner’s system and the types and manner of prohibitions on such conduct.[8]
While the law in this area becomes more settled, entities contemplating using scraping programs to access a public web site should also consider whether such action is authorized by reviewing the terms of use and other terms or notices posted on or made available through the site. In the latest ruling in the Cvent, Inc. v. Eventbrite, Inc. In the United States district court for the eastern district of Virginia, the court ruled that the terms of use should be brought to the users' attention In order for a browse wrap contract or license to be enforced.[9] In the plaintiff's website during the period of this trial the terms of use link is displayed among all the links of the site, at the bottom of the page as most sites on the internet. This ruling contradicts the Irish ruling described below. The court also rejected the plaintiff's argument that the browse wrap restrictions were enforceable in view of Virginia's adoption of the Uniform Computer Information Transactions Act (UCITA)—a uniform law that many believed was in favor on common browse wrap contracting practices.[10]
Outside of the United States, in a February, 2006 ruling, the Danish Maritime and Commercial Court (Copenhagen) found systematic crawling, indexing and deep linking by portal site ofir.dk of real estate site Home.dk not to conflict with Danish law or the database directive of the European Union.[11] In February, 2010, the Irish High Court in the case of Ryanair Limited v Billigfluege.de GmbH. This case established a precedent by acknowledging that the Terms of Use on Ryanair’s website, including the prohibitions contained in those Terms of Use against screen scraping. The case is currently under appeal in the Supreme Court. In Australia, the Spam Act 2003 outlaws some forms of web harvesting, although this only applies to email addresses.[12][13]
The administrator of a website can use various measures to stop or slow a bot. Some techniques include: