XPath vs. CSS Selectors: Which Selector Is The Best?
Web scrapers are invaluable for online research, but only if they can complete the task. It’s not unusual for websites to occasionally block your scraper, but it shouldn’t be a regular occurrence. If your crawler gets blocked frequently, you might need to change how your bot uses selectors.
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There are two kinds of selectors used by most web scrapers: XPath and CSS. Here’s what you need to know about why your web crawler is being detected, why selectors matter, and how to choose between CSS and XPath selectors.
Why Is Your Crawler Being Detected?
There are a few reasons why your web crawler is getting detected. Websites pay attention to user behavior to spot when a visitor is a bot instead of a human. When sites detect bots, they usually block them in case the bot is a malicious virus or attack.
Most sites look for bots by monitoring four behaviors:
- Visitor IP addresses: An IP address is essentially your network’s identification number. If the same IP address is doing a lot of suspicious activities or many activities at a fast pace, websites may block it entirely.
- Browser user agents: A browser user agent is an even more specific identifier, naming the browser platform and version and the operating system. Suspicious user agents like those from headless browsers may make your bot more likely to get spotted and blocked.
- Site cookies: Websites can save cookies to your computer to track your behavior. If you scrape the same site twice without wiping cookies, your bot is more likely to get blocked based on those cookies.
- Visitor behavior: Most importantly, how your bot behaves can give it away. Visiting too many pages of a site too quickly or interacting strangely with CSS selectors can make it obvious that your program is a bot and not a person.
Web scrapers need to collect a lot of information to be worthwhile. Many scraping programs target hundreds of pages per scrape. If they get blocked halfway through the process, you’ll wind up with a dataset that’s significantly less useful than you wanted.
Why Selectors Matter When Web Crawling
One of the best ways to reduce how often your bot is detected is by changing the selectors you use. Selectors are a basic component of web scrapers. They “select” the parts of the page you want to study so the bot can copy them. Without selectors, scrapers can’t review a webpage and collect specific data.
A selector looks for a specific string or component within a webpage. For example, a selector might look for particular CSS attributes like “bgcolor” or tag names like “<h3>” to find relevant data. Whenever they spot the relevant tag, they copy everything it applies to.
Selectors are also one of the most common reasons your web scraper may be detected. Scraping programs interact with a website in two ways:
- Sending an initial server request to load the page
- Crawling the page with selectors to find data
These interactions are the two points when a website can track your behavior and label it suspicious.
Use selectors properly and prevent bots from getting detected
If your bot is protected behind rotating residential proxies, it’s unlikely that the server requests are causing the blocks. It’s more likely that something about how your selectors interact with the website seems suspicious.
You can fix that by changing how your bot uses selectors. To do that, it helps to understand the differences between CSS and XPath selectors, how they work, and when they look suspicious to websites.
Protecting Web Crawlers from Detection: Choosing XPath vs. CSS Selectors
There are two main ways a web crawler can scan for data on a webpage: XPath formatting or CSS formatting. Both of these methods work well if you execute them correctly, but you need to be cautious to make sure you’re not making your bot more likely to get spotted.
How web crawlers use XPath
XPath is short for “XML path.” XML is one of two major languages that browsers use to display websites. XPath is a language specifically designed to navigate XML documents and find data within them.
XPath finds specific XML and HTML elements within a page. An XPath selector scans the entire page, generating a “path” through the XML document.
An excellent element of XPath is that it allows your scraper to go both up and down the Document Object Model (DOM), which represents the page’s programming. If you imagine a website’s code as a tree, XPath can go up and down different branches to find everything you need.
The biggest problem with XPath is that it’s complicated. To properly implement XPath selectors, you’ll need to do a lot of work and testing to make sure they’re collecting the information you want.
How web crawlers use CSS selectors
CSS stands for “cascading style sheets.” HTML webpages use CSS to improve their appearance. Many websites have specific CSS attributes, classes, or IDs to make important page information stand out. For example, titles and headers often have special CSS identifiers that can be used to find them on the page.
That’s what CSS selectors look for. As a bonus, CSS selectors are easy to implement and read. If you’ve never written a scraper or you don’t have a ton of time, CSS selectors are the fastest solution for your bot. However, these selectors only go from parent nodes to child nodes. A CSS selector can’t “back up” the DOM to include information outside of that node on other parts of a page. Once it runs out of data within a node, it’s done.
CSS selectors are also much more likely to trigger website blocks. That’s because CSS selectors are prone to triggering “honeypot” traps hidden in website CSS that specifically spot and block web scrapers. These traps are less likely to catch XPath selectors because of the difference in navigational styles.
Comparing XPath vs. CSS selector performance
Both XPath and CSS selectors are valuable when you’re scraping web pages. When deciding which kind of selector to use, it’s essential to compare their performance in your specific circumstances.
- Flexibility: In general, XPath is more flexible because it allows you to use the “contains” command to find partial matches when crawling sites.
- Speed: Looking for CSS selectors is faster than using XPath because of how the crawlers operate.
- Simplicity: Coding a scraper to look for CSS selectors is significantly easier than XPath, especially for people who are relatively new to programming.
- Browser type: XPath is compatible with old browsers, but it needs to be reworked for each program’s browser. CSS may not be compatible with the oldest browsers in use, but it’s consistent across modern browsers.
- Navigation: With XPath, it’s possible to navigate up the Document Object Model (DOM) tree, while CSS only lets you navigate down it.
- Detection: Bots searching for CSS selectors can trigger honeypot traps, causing websites to detect and ban IP addresses. This is less likely with XPath.
When comparing the two, XPath is better for crawlers that need more flexibility and protection. CSS selectors are a better choice for scrapers that prioritize speed and simplicity.
Avoid Website Detection with Scraping Robot
Choosing the right selectors can be a lot of work. You don’t have to do it by yourself, though. Let Scraping Robot take care of the entire scraping process for you.
You can work with Scraping Robot to design the perfect scraper for your needs. All you need to do is explain what data you want to collect and how often you want it to the Scraping Robot team. They will create a customized scraper to your exact specifications. They’ll also handle choosing and programming the selectors to minimize the risk of your scraper getting spotted by the websites you’re studying.
The best proxies with Scraping Robot
Scraping Robot can help protect your bot from being detected in other ways, too. These scrapers come with proxies automatically built-in. Scraping Robot works with Rayobyte to provide secure rotating residential proxies that keep bots from getting spotted and blocked due to server requests. Even if one proxy IP address does get blocked, the bot automatically swaps in another, so your scrape continues without a hitch.
Coupled with the best proxies available, Scraping Robot crawlers are the most reliable and efficient way to collect data online. No matter what kind of information you want to collect, a Scraping Robot program will help you gather it efficiently and without unnecessary delays.
Avoid the Hassle of Choosing Selectors with Scraping Robot
You have enough on your plate and trying to decide between little things like formats, like xpath vs css selectors, can make things more difficult. There’s no reason you should have to build a web scraper from the ground up or fiddle with selectors to perform research. You can work with Scraping Robot to make the entire scraping process that much simpler.
Even better, the first 5,000 scrapes you perform with Scraping Robot are free. You can test out how Scraping Robot improves your research flow without risk. Get started today to discover how Scraping Robot can make the data collection process that much smoother.
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