Web scraping also known as web harvesting or web data extraction means downloading structured data from the web, selecting some of that data, and passing along what you selected to another process.It used for extracting data from websites.For example, weather reports, auction details, market pricing, or any other list of collected data can be sought in Web scraping efforts.
Uses of Web Scraping:-
- Recruitment: Searching for jobs,candidates.
- Real Estate: Determining Sales price over time, rental amount over time.
- Search Engine Optimization(SEO): Scraping Google, Bing, and Yahoo for your sites ranking for a given keyword.
- Social Media: Downloading latest tweets from twitter,obtaining job post and candidate information from LinkedIn,etc.
- Banking: Downloading desired transaction information using fin-tech products like Mint and Pocketwise.
Is web scraping legal?
Well, answer to this question is both yes and no.That is,if it is used for public purpose then its legal but if it used for personal purpose then it is illegal. Because the data displayed by most website is for public consumption. It is totally legal to copy this information to a file in your computer. But it is regarding how you plan to use this data that you should be careful about.If the data is downloaded for your personal use and analysis, then it is absolutely ethical. But in case you are planning to use it as your own, in your website, in a way which is completely against the interest of the original owner of the data, without attributing the original owner, then it is unethical, illegal.
Tools for Web scraping:-
- Heritrix is a web crawler designed for web archiving, written by the Internet Archive.
- OutWit Hub is a web scraping application including built-in data, image, document extractors and editors for custom scrapers and automatic exploration and extraction jobs (free and paid versions).
- HtmlUnit is a headless browser that can be used for retrieving web pages, web scraping,and more.
- HTTrack is a free and open source Web crawler and offline browser, designed to download websites.
- Wget is a computer program that retrieves content from web servers. It supports downloading via the HTTP, HTTPS, and FTP protocols.
- Mozenda is a WYSIWYG(pronounced “wiz-ee-wig” is acronym of ‘What You See Is What You Get’) software that offers cloud, onsite, and data wrangling services.
- Selenium is a portable software-testing framework for web applications.Data Toolbar is a web scraping add-on for Internet Explorer, Mozilla Firefox, and Google Chrome Web browsers that collects and converts structured data from web pages into a tabular format that can be loaded into a spreadsheet or database management program.
- Curl (Client URL) is a computer software project providing a library (libcurl) and command-line tool (curl) for transferring data using various protocols.
- iMacros is an extension for the Mozilla Firefox, Google Chrome, and Internet Explorer web browsers, developed by iOpus/Ipswitch. It adds record and replay functionality similar to that found in web testing and form filler software.
Advantages of web scraping:-
- Inexpensive – Web scraping services provide an essential service at a low cost. It is paramount that data is collected back from websites and analyzed so that the internet functions regularly. Web scraping services do the job in an efficient and budget friendly manner.
- Easy to implement – Once a web scraping services deploys the proper mechanism to extract data, you are assured that you are not only getting data from a single page but from the entire domain. This means that with just a onetime investment, a lot of data can be collected.
- Low maintenance and speed – One aspect that is often overlooked when installing new services is the maintenance cost. Long term maintenance costs can cause the project budget to spiral out of control. Thankfully, web scraping technologies need very little to no maintenance over a long period. Another characteristic that must also be mentioned is the speed with which web scraping services do their job. A job that could take a person week is finished in a matter of hours.
- Accuracy – The web scraping services are not only fast, they are accurate too. Simple errors in data extraction can cause major mistakes later on. Accurate extraction of any type of data is thus very important.In websites that deal in pricing data, sales prices, real estate numbers or any kind of financial data, the accuracy is extremely important.
Disadvantages of web scraping:-
- Difficult to analyze – For anybody who is not an expert, the scraping processes are confusing to understand. Although this is not a major problem, but some errors could be fixed faster if it was easier to understand for more software developers.
- Data analysis – The data that has been extracted will first need to be treated so that they can be easily understood. In certain cases, this might take a long time and a lot of energy to complete.
- Time –Sometimes web scraping services take time to become familiar with the core application and need to adjust to the scrapping language. This means that such services can take some days before they are up and running at full speed.
- Speed and protection policies – Some websites do not allow screen scrapping. In such cases web scrapping services are rendered useless. Also, if the developer of the website decides to introduce some changes in the code, the scrapping service might stop working.