Many people interested in data extraction think that scraping and crawling are the same, and you can often find people online using these terms interchangeably. However, these two terms denote different things.
This misconception leads to all kinds of mistakes that can cost individuals and businesses alike. We’ll give you all the essentials you need about scraping and crawling so that you don’t make these mistakes.
This article will help you use proper terminology and find the right solutions for your needs, but before we get to the differences, let’s see what a web scraper is.
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What is web scraping?
Web scraping is a data extraction process used for gathering information from a variety of websites. It’s also called web data extraction or web harvesting. Scraping is done with web scraping software that can create a direct connection with the web using a browser or HTTP protocol.
Even though you can do crawling manually today, it’s usually an automated process. Scraping includes copying data from the web and storing it into a spreadsheet or a local database. The data is later used for analysis and insights.
What is a web crawler?
Crawling, on the other hand, is also done using software or bots to browse the web. These tools let users browse many websites quickly and in an automated fashion. One of the most common uses for web crawlers is website indexing.
Google uses crawlers to index web pages and ranks them in searches. The sheer number of new websites and their frequent changes make indexing absolutely necessary. Web crawlers download the contents of web pages and learn what kind of information they contain.
How they work
Now when we’ve answered what a web crawler is and scraper, let’s see how they operated behind the scenes.
There are different techniques that scrapers use to gather data. Many scrapers use Python or other programming languages for their regular expression matching systems to collect data on the web. That’s a very simple approach but effective.
Some scrapers use socket programming to make HTTP requests to remote servers to acquire dynamic or static pages. Overall, scraping tools are being developed quickly, and there are many different variations.
Web crawlers start their operations by going through a list of URLs. These first URLs are known as “seeds”, and the crawler recognizes all their hyperlinks, adding them to the whole URL list. Crawlers recursively visit these new URLs while following specific guidelines.
If the crawler is doing web archiving or archiving sites, it will also save and copy all the information during the process. Archives can be navigated through, read, and viewed. All the pages are stored separately using HTML format. Read on what is a web crawler method to find out more about the subtopic.
Although they have similarities, crawling and scraping are pretty different. They have two essential differences:
Web scraping is all about gathering valuable and relevant data. All data fields that you need to extract from a set of websites are determined before the process starts. The domain names of all the sites that are scraped are known as well.
On the other hand, in crawling, the domain names and URLs of individual pages are unknown. That’s because the goal of crawling is actually to find URL addresses or sites and their page. Scraping already has the sites that contain relevant data and just need to extract information.
Crawling is actually about discovering sites. For example, crawling could be used to create a list of certain sites that you could use for scraping specific data.
In web crawling, the results or output is quite standard – you get a list of URL addresses. You can include additional information and fields, but the core results are the URLs. Web scraping can have many more fields that can contain various types of data.
A typical scraping process can have from 5 and up to 20 data fields depending on the application and desired information. For example, fields can contain product names, their size, weight, material information, price, and much more.
Scraping is more focused, while crawling goes through all page subsets to scan and learn about the site’s data. That’s why they provide such different information in the end.
We hope this post has helped you understand the differences between these two tools. When you are looking for either of these solutions, make sure to remind yourself about these core differences so that you can choose the right option for your intended application.