What is the difference between web crawling and scraping? That's a common doubt, and you're not the only one who has asked that question. The reason is that the terms are often used interchangeably, yet they differ!
Understanding the difference is critical, especially if you want to extract data from one or more target websites. In this article, you'll dig into web crawling vs. web scraping.
Let's dive in!
Quick Answer: Crawling vs. Scraping
In short, web crawling involves discovering URLs or links, while web scraping is extracting data from a website. In most web data extraction projects, you need both crawling and scraping.
A web scraping process generally follows the logic below:
- Crawl a site to discover the URLs of new web pages.
- Follow those URLs and download the corresponding HTML files.
- Perform data scraping by parsing the HTML documents and extracting data from them.
As you can see, crawling is usually part of web scraping when the target website consists of several web pages. You must first crawl the site to discover them to scrape them all.
You're now ready to jump into the more detailed web crawling vs. web scraping comparison!
What Is Web Crawling?
Web crawling is programmatically browsing the internet to discover new pages. Its purpose is to create an index of all existing pages. In web scraping, it's applied to one or more specific sites to discover the page from which to extract data.
A web crawler, or spider, generally starts by visiting a few seed URLs of a specific site. From there, it'll discover and follow hyperlinks to other pages until it has found all pages of interest.
Crawling the web has several applications, including creating an index of web pages and monitoring site changes. Both play a key role when it comes to web scraping.
Learn how to crawl sites in Python in our step-by-step tutorial.
What Is Web Scraping?
Web scraping is the process of extracting data from a target site. That's usually performed by automated software called a web scraper. Such a tool can parse the HTML content of a web page and retrieve data from it.
A scraper starts by connecting to the web pages of interest. To discover them, it generally relies on web crawling. Then, it uses CSS selectors or similar methods to select HTML elements and get the desired data from them.
Users and businesses use scraping to collect and analyze web data for a variety of purposes. Those include price monitoring, content aggregation, lead generation, and market research, among others. Check out our in-depth guide to learn more about web scraping and its most popular use cases.
Also, you might be interested in our introductory Python web scraping tutorial.
Summary of Web Crawling vs. Web Scraping
The following table summarizes the main differences between the two concepts:
| Web Crawling | Web Scraping | |
|---|---|---|
| Purpose | Finding new web pages | Extracting specific data from web pages |
| Performed by | Automated crawling bots | Automated scraping scripts |
| Process | Following links to build a map of URLs | Parsing HTML content to extract data using specific instructions |
| Result | A list of web pages | Data in JSON, CSV, or similar formats |
Common Challenges of Web Scraping and Web Crawling
Web scraping and crawling have something in common: they're performed by an automated tool. Because of that, they share the same challenges. Namely, you'll likely get blocked on sites that use anti-bot technologies, and most popular sites have those set in place.
The anti-scraping measures can detect your automated software as a bot. To do so, they monitor the user's behavior and HTTP traffic to look for suspicious patterns or rely on JavaScript challenges and CAPTCHAs, to mention some examples. Take a look at our guide to learn about the most common anti-scraping techniques you need to know.
When an anti-bot solution flags your script as a bot, it can prevent it from accessing the site. For example, blocking your IP for a while or banning it forever. That can occur during both crawling and scraping.
To avoid getting blocked, you should follow some web scraping best practices. If those aren't enough, you'll need a more advanced solution, like ZenRows. This powerful scraping API can bypass any anti-bot solution for you!
Conclusion
You learned about key web data extraction concepts in this web crawling vs. web scraping guide. You started with a quick comparison and then dove into scraping and crawling in depth!
Now you know:
- What web crawling is.
- What web scraping is.
- The main difference between them.
- What the two have in common.
Regardless of whether you're scraping or crawling, some technologies can detect and block it. Avoid any obstacles with ZenRows, a next-generation scraping tool with built-in IP rotation, premium proxies and other must-have features. Crawling and scraping have never been easier!
Frequent Questions
Is Web Scraping the Same as Web Crawling?
No, web scraping isn't the same as web crawling. The latter is about exploring the web to discover new pages, while web scraping involves retrieving data from HTML documents. Scraping generally involves and requires web crawling, thus web crawling is a subset of web scraping.
What Is a Crawler vs. Spider vs. Scraper?
A crawler, spider, and scraper are all automated bots used to gather information from the web. A crawler and spider are often used interchangeably and refer to bots that do web crawling. A scraper is an automated script that runs web scraping.
What Is the Difference Between Data Scraping and Web Scraping?
The main difference between data and web scraping is that the former is about extracting data from any source. That can be a text document, PDF, spreadsheet, or multimedia file. Web scraping refers instead to the specific process of retrieving data from the web. Thus, web scraping is a specialization of data scraping.
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