How to Block Web Crawlers From Your Website

Bot management Cyberfraud Scraping

Web crawlers automatically scan websites to collect data—some are beneficial (like Googlebot for SEO), while malicious ones steal content, scrape data, and degrade site performance. Bot attacks nearly doubled in 2023, with a 32% surge by year-end, making crawler management critical for website security.

Key takeaways:

Good vs. bad crawlers: Allow legitimate search engine bots while blocking malicious scrapers and content thieves
Methods to control crawlers: Use robots.txt, .htaccess files, CAPTCHA alternatives, or bot management solutions
Important caveat: Robots.txt provides no security—it only requests compliance
Best protection: AI-powered bot management solutions like DataDome block malicious crawlers in under 2 milliseconds while allowing verified good bots
Business impact: Automated bot management saves engineering teams significant time previously spent on “whack-a-mole” manual blocking

What is a web crawler?

Web crawlers “crawl” all over the internet, cataloging information for purposes such as search engine optimization (SEO). With bot attacks nearly doubling throughout 2023 and reaching peak activity with a 32% increase by year-end, understanding which crawlers to allow and which to block has become a critical cybersecurity priority.

They can extract data from web applications, assess navigable paths, read parameter values, perform reverse engineering, and more. Not all crawlers are bad—in fact, the Googlebot crawler should be allowed on your site if you want to rank in Google search results. (Just make sure it’s actually the real Googlebot!)

While there is some level of distinction between web crawling and web scraping, the type of bot is often very similar. Crawlers look for interesting data, and scrapers take it.

Why Would You Need to Block Crawlers From Your Website?

Blocking malicious bots and bad crawlers from your website is a common practice to maintain the security and integrity of your site. Here are some reasons why you might want to block such crawlers. The financial impact of uncontrolled bot activity is substantial. Global losses from bot attacks range from $68 billion to $116 billion annually, with U.S. companies alone losing $18 billion to $31 billion each year due to AI-based automated attacks. Managing bot traffic has evolved from a minor inconvenience to a significant operational challenge.

Protect Your Data

Bots can be used for malicious purposes such as stealing data and scraping content from websites. As a result, website owners may find it necessary to block crawlers from their websites in order to protect their information and keep their site secure.

Ensure Website Performance

Blocking crawlers can help improve the performance of your website by reducing the amount of unnecessary traffic generated by automated requests. Ultimately, blocking crawlers can be a valuable tool in protecting your website’s data and maintaining its performance.

Limiting Bad Bots

By preventing malicious bots from accessing sensitive parts of your website, you can ensure that your information isn’t compromised—and that your visitors remain safe while they browse your site.

How to Prevent Bots from Crawling Your Site

Blocking web crawlers can be done through various methods. However, it’s important to approach this cautiously, as blocking all crawlers can negatively impact your site’s visibility on search engines. Instead, consider using methods that allow you to control crawler access to specific parts of your site. Here are some common approaches:

1. Use Robots.txt

Robots.txt is a simple text file that tells web crawlers which pages they should not access on your website. By using robots.txt, you can prevent certain parts of your site from being indexed by search engines and crawled by web crawlers.

It’s important to note that robots.txt does not provide any type of security, but it can help protect sensitive or confidential information from being exposed to the public internet. It can be an effective tool for controlling how search engine bots crawl and index your website content.

When creating a robots.txt file, it’s best practice to use specific rules for each bot you wish to exclude from crawling your site, along with wildcard directives where applicable.

"Our first experience with scraper bots was as much as 15 years ago. However, at the time, it was much easier to identify and block them than it is today. Over time, the growing range of different bots and their increasing scraping frequency became more and more problematic. Managing our bot traffic became a very time-consuming, nerve-wracking whack-a-mole game, and an endless arms race."

Uwe Hörmann

Co-Founder & Partner at Toppreise

Learn more

2. Use Hypertext Access File

In addition to robots.txt, you can also block web crawlers using your .htaccess file. The .htaccess file is a powerful configuration file for the Apache web server, and it controls how requests are handled on the server.

You can use directives in your .htaccess file to block access for specific user agents or IP addresses. This is useful when you want to prevent certain bots from crawling your site without having to make changes in multiple places (like with robots.txt).

Blocking web crawlers via either robots.txt or .htaccess will not guarantee they won’t visit your website, but it can give you more control over which parts of your site get indexed by search engines.

3. Use a CAPTCHA Alternative

CAPTCHAs prevent bad bots from crawling a website by introducing challenges that are easy for humans but difficult for automated scripts to solve. These challenges, such as distorted text, image recognition, interactive tasks, and temporal elements, require human-like cognitive abilities and real-time adaptability.
In the age of AI, traditional CAPTCHA puzzles are no longer a reliable defense. Bots can now solve challenges faster and more accurately than humans. This is why modern protection focuses on behavioral analysis rather than asking users to solve frustrating puzzles.

DataDome’s CAPTCHA alternative is a simple, frictionless slider that is part of a verification-first approach. For most users, protection is completely invisible. Only suspicious traffic is presented with the slider, which collects behavioral signals like mouse movements and touch dynamics to confirm if the user is human. This approach stops sophisticated bots without disrupting the experience for legitimate users.

datadome-captcha

4. Invest in a Bot Management Solution

For the most comprehensive protection against unwanted or malicious web crawlers, a specialized bot management solution is necessary. Unlike manual approaches that consume significant engineering resources, modern bot management platforms provide automated, real-time protection.

“We like to focus our engineering efforts in our domain of expertise, which is not fighting bots,” explains Nick Johnson, Software Engineering Manager at Carsforsale.com. “There have always been bots around. We knew and could see bad actors coming into our systems, but staying on top of those and mitigating all the new ones coming in was just too big of a challenge. It was also taking away from our core competencies.”

A specialized bot management solution provides robust security measures to protect your site from malicious bots while giving you control over which bots are allowed to crawl your site and how often they can visit. By implementing comprehensive bot protection, you can be sure that only authorized web crawlers (like Googlebot) have access to your content.

DataDome-Dashboard

DataDome is a leading cyberfraud protection platform named a Leader in The Forrester Wave™ for Bot Management Software, trusted by companies like Tripadvisor, Zocdoc, and SoundCloud. The platform uses bot and agent trust management software to protect websites, mobile apps, and APIs against automated threats.

Block Web Crawlers FAQ's

What's the difference between web crawling and web scraping?

Web crawling refers to the automated process of systematically browsing and indexing web pages, typically for legitimate purposes like search engine indexing. Web scraping specifically focuses on extracting and collecting data from websites, which can be done for both legitimate and malicious purposes. While the bot technology is often similar, crawlers look for interesting data, and scrapers actively take it.

Can robots.txt completely block malicious bots?

No. Robots.txt does not provide any security—it’s simply a request that well-behaved crawlers comply with. Malicious bots routinely ignore robots.txt directives. It’s useful for guiding legitimate search engine crawlers but should never be relied upon as a security measure against bad actors.

How do I know if my website has a bot problem?

Common signs include unusual traffic spikes, degraded website performance, competitors displaying your pricing or content, inflated analytics data, and increased server costs. A bot management solution can provide detailed visibility into automated traffic attempting to access your site. According to industry data, bot attacks nearly doubled in 2023, so most websites face some level of bot activity.

Will blocking bots hurt my SEO?

Not if done correctly. The key is allowing legitimate search engine crawlers (like Googlebot, Bingbot) while blocking malicious bots. Advanced bot management solutions like DataDome can distinguish between good and bad bots, ensuring search engines can still index your content while malicious scrapers are blocked.

What's the best method to block web crawlers?

The most effective approach combines multiple methods: use robots.txt for legitimate crawler guidance, implement .htaccess rules for specific blocks, deploy a CAPTCHA alternative for suspicious activity, and invest in an AI-powered bot management solution for comprehensive, automated protection. Enterprise-grade solutions like DataDome analyze every request in real-time, blocking malicious crawlers in under 2 milliseconds while allowing verified good bots through.

How much time does manual bot management take?

According to companies managing bots manually, it can consume significant engineering resources. One travel technology company reported that their engineering team was spending time on constant interventions—what they described as a “time-consuming, nerve-wracking whack-a-mole game.” Automated bot management solutions eliminate this burden, allowing teams to focus on core business activities rather than playing defense against evolving bot threats.

Are AI-powered bots harder to block than traditional bots?

Yes. AI has made bots significantly more sophisticated. U.S. companies lose $18 billion to $31 billion annually due to AI-based automated attacks. Traditional blocking methods like CAPTCHA puzzles are increasingly ineffective against AI-powered bots that can solve these challenges. Modern bot management requires AI-powered detection that analyzes behavioral signals and intent, not just puzzle difficulty.

How does DataDome block web crawlers without affecting legitimate users?

DataDome’s bot protection solution uses a multi-layered AI detection engine that analyzes 5 trillion signals daily to distinguish between legitimate users and malicious bots. The platform blocks threats in under 2 milliseconds with a <0.01% false positive rate. It automatically allows verified good bots (like search engine crawlers you’ve whitelisted) while blocking malicious scrapers, content thieves, and other unwanted automated traffic—all without disrupting the experience for real users.