Web Crawling vs Web Scraping

web crawling vs web scraping
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It is easy to mistake web scraping and web crawling. These two terms are intertwined and the processes often go together. It doesn’t help that many sources use them interchangeably and include crawling as a part of web scraping. 

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But knowing the differences is critical if you are planning to start collecting data and making better informed, data-driven decisions. This article will untangle web crawling and web scraping and outline their most crucial aspects and differences.

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What is Web Crawling?

Web crawling is the process of using bots to scan websites, index web data and look for more pages to visit. Bots “crawl” through the World Wide Web as if a spider would. Therefore, they are frequently called “crawlers” or “spider bots”. 

 

These bots can reach every corner of the internet, leaving no web pages untouched. As a result, it is common for search engines like Google and Yahoo to use web crawling.

 

Crawlers usually archive web data in its entirety – from meta tags and textual content to URLs of other pages where it can continue web crawling. In some cases, the crawled information is offline – then it is called data crawling instead of web crawling.

 

The amount of data to crawl is almost limitless because websites are interlinked, and data crawling bots can jump from one to another effortlessly. Thus, web crawling is only possible with bots, and you can’t achieve it manually.

How does Web Crawling work?

1. A list of websites

The initial list of website addresses (URLs) is called a seed list, which is later updated with new websites. It also contains rules on what is the order of pages visited, how often they should be crawled, and what should be the priorities on each page. The entire structure is called a crawl frontier.

2. Loading and indexing

Web data crawling requires loading (fetching) a website and all of its elements just like a browser would. Then, through a process called parsing, the bot rearranges the broken down pieces of code. Parsing allows the bot to read, index and present the needed web data to humans in an easy to understand way.

3. Finding further targets

At the same time as parsing the web pages, the bot finds other active URLs and updates the crawl frontier, creating a new queue. Then, the data crawling bot can repeat the process again. 

 

Web crawling stops when priorities are achieved or when new addresses end. But the journey of a crawler bot might come into endless loops also. For example, pages might be linking to one another, resulting in a crawler bot visiting them continuously. Deduplication is necessary for the crawler bot to avoid such loops as it checks whether the page was crawled before.

What is Web Scraping?

Web scraping is the process of collecting and extracting web data from the internet to your computer, database, or website. If the data is stored offline, it is called data scraping or data extraction.

 

We can understand web data extraction as the equivalent of copying the needed data and pasting it to your computer. Technically, you can perform web scraping manually, but it takes more time and effort. 

 

However, it’s nearly impossible to use manual scraping to collect data at any larger scale. So, web scraping tools aim to make data gathering automatic and effortless. They might even import the data into a spreadsheet or a database for analysis afterwards. 

 

A web scraper can help companies gather data for later use in making data-driven decisions. Businesses that use these tools have a competitive edge over those that miss the opportunity, as they know more about their competition, customers and market conditions overall.

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How does Web Scraping work?

1. Loading target URLs.

First, the scraper bot loads the needed page. Usually, the HTML format is loaded, but advanced scrapers can also load elements in Javascript or CSS. Similarly to a crawler, the web scraper then downloads the website to local memory, but instead of collecting more URLs, it moves to the next step.

2. Extracting data

The scraper bot extracts all or part of the webpage’s data. Usually, a specific dataset is needed, so the parameters are specified. As such, the data scraping process can return only what was required.

3. Converting data

Web scraping software can convert the scraped data into several formats. Often, it’s a simple CSV format for the data to be analyzed in a spreadsheet. However, other formats, such as HTML, XML, or JSON, can be handy with more advanced software. Finally, a web scraper may collect some URLs from the website to continue data extraction if needed.

 

The scraped data is not limited only to textual content, so more advanced web scraping software can extract images, videos and anything else on the website. All of these bots require deep coding and software development knowledge.

 

Luckily, there are options for those of us who are less tech-savvy. Ready-to-use web scraping tools don’t require much coding experience and can work with minimal maintenance. Check out our article on web scraping techniques to learn more.

Web Crawling vs Web Scraping

Now we can put both definitions side by side for comparison. Web crawling refers to checking pages and indexing them, while web scraping focuses on extracting the web data. To simplify, by web scraping, you take what you know is available, and by crawling, you look around to make a list.

 

These terms are often confused as it is common to crawl the website first and then scrape it. Knowing what data is available allows web scraping to do exactly what is needed. However, data crawling is not a requirement before scraping as smaller projects can be successful without it.

Crawling

Scraping

Can only be done online

Used for offline databases also

Requires a bot

Bots are preferred but can be done manually

Deduplication is necessary

Deduplication is not necessary

Visits every page of a website

Can focus on a target dataset

Most often used by search engines to index the web

Used by businesses and individuals for data collection

Most Common Uses of Web Scraping

Equity research

You need to know a lot of information about a company before investing. Traditionally, stock market data was stored in financial statements or business briefs. Nowadays, however, data appears in online news outlets, social media, or forums. Web scraping can help you gather such data efficiently, enabling profitable decisions.

Market research

A lot of business-related activities these days happen online. Any such data can be extracted quickly using web scraping. Whether it’s competitor prices, trends or product data – all of it can be delivered with minimal hassle. Some applications, such as retail marketing, use web scraping to create product descriptions, manage assortment and monitor minimum advertised pricing (MAP).

Machine learning

Machine learning rests on the idea that computer systems can learn from data. While enormous amounts of data are needed for progress to happen, web scraping can solve this issue. For example, linguists scrape the internet for natural language expressions, and through machine learning, the model can start recognizing and using them.

Brand protection

Someone might use your company’s good name illicitly and harm your reputation. Copyright infringements, ad fraud and counterfeit products are only a few examples. Web Scraping will allow companies to gather the required data quickly and move on to legal action faster. 

Most Common Uses of Web Crawling

The best-known use of web crawling is internet indexing – the creation of a list of available web data. Search engines use these indexes by associating them with keywords visitors use while searching.

 

Crawler bots surf the internet regularly, indexing all the websites, and once they find information relevant to a search term, the associated results page is updated.

 

Many search engine optimization (SEO) tools use the same automated process to crawl (with web scraping in tandem) the search engine results page, finding keywords and competitors. With accurate data, businesses can improve their search results ranking and increase their websites traffic.

 

Successful SEO efforts require a lot of content that you should organize for search engines to find. Web crawling helps marketers perform on-site SEO analysis and test how well the content is optimized for bots to crawl. A crawler can locate broken links, test the sitemap, and show the overall website’s speed.

Is Web Scraping and Crawling legal?

Web scraping and web crawling aren’t illegal as such. No one will raise any objections if you crawl and scrape publicly available data or your website. However, there are exceptions.

 

Many websites specify in their Terms and Conditions whether automated data collection is permitted. So, a general rule of thumb is not to use bots for data that is only accessible after logging in, as that makes you subject to their Terms of Service.

 

However, other sites impose such rules without any log-ins or contain content that may be subject to copyright. Such exceptions are all over the internet, and every case is a unique one. We recommend always seeking professional legal advice.

Final thoughts

Web scraping vs web crawling describes two different processes. The first looks and indexes the web, and the latter can extract the data. Some confusion arises because scraping may require some crawling first.

 

The many uses of web scraping make it an essential tool for businesses and individuals, while web crawling is crucial for search engines to work and provides a way to use them to your advantage.

 

Both have some legal concerns, so you should double-check before starting your projects. But even legal web scraping and web crawling can be unwanted for websites. Use datacenter proxies to be more effective, and avoid IP blocks.

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