Web crawlers, also known as bots or spiders, are programs that automatically browse the internet. They go from one web page to another by following links. The main job of these crawlers is to collect data from websites so that search engines like Google can store and organise it. This helps search engines show the right results when people search for something online. A crawler list, which includes the names and user agents of various bots, is often used by website administrators to monitor or control crawler activity on their sites.
Modern websites depend on being seen by these bots. If a site isn’t crawled properly, it might not show up in search results, which means fewer people will visit the site. That’s why web crawlers—and knowing what’s in your crawler list—are so important for businesses and websites that rely on online visibility.
Knowing how crawlers work gives you a big advantage. If you understand what they look for and how they behave, you can make small changes to your website that help it get more attention from search engines. This can lead to better rankings, more visitors, and possibly more sales.
Web crawlers—also known as spiders, bots, or search engine crawlers—are automated programs that browse the internet to collect and index content. They play a vital role in SEO, helping search engines understand and rank websites based on structure, content quality, and metadata. Whether you’re managing a WordPress site, running an eCommerce store, or optimizing a blog, it’s crucial to know which crawlers are accessing your site. This comprehensive crawler list covers the most common search engine bots, SEO tools, and user-agents that interact with your site—some to help your rankings and others that may slow down your server or collect data without permission.
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What Are Web Crawler Bots?
Web crawlers are software programs made to browse the web automatically. They visit websites, read the content, and send the information back to search engines or other platforms. This process helps search engines build a huge database of all the websites on the internet.
There’s a difference between search engine crawling and web scraping. Crawling is usually done by search engines like Google to index websites and help users find useful content. Scraping, on the other hand, is often done by third-party bots that copy content or data without permission, and it may be against a site’s rules.
While crawlers are useful for search engines, not all bots are good. Some bots are helpful and follow the rules, while others are harmful and steal data or slow down websites. Understanding what type of bot is visiting your site is an important part of managing your website’s performance.
Why Monitor Web Crawlers?
Monitoring web crawlers helps website owners understand how their content is being discovered, indexed, and analyzed. Some crawlers, like Googlebot or Bingbot, are essential for SEO. Others may belong to analytics tools, uptime monitors, or even bad bots that scrape content or overload servers. By reviewing this user-agent list, you can make informed decisions about which bots to allow, throttle, or block using your site’s robots.txt or security plugins.
- Key reasons to monitor crawler activity:
- Optimize crawl budget and page indexing
- Detect suspicious bot traffic or scraping
- Improve server performance and page load time
- Secure sensitive or private content from unwanted access
The Ultimate Web Crawler List (2025 Update)
Understanding which bots and crawlers visit your website is essential for SEO, site speed, and security. Some bots help search engines index your site, others analyze backlinks or keyword data, while some may be harmful and need to be blocked. Here’s a comprehensive crawler list broken into useful categories for site owners, marketers, and developers.
1. Common Search Engine Bots
These are the official search engine crawlers that scan and index websites for inclusion in their respective search results. They’re the most important bots to allow via your robots.txt file.
- Googlebot – Used by Google to index websites. It has desktop and mobile variants.
- Bingbot – Microsoft’s crawler for the Bing search engine.
- Baiduspider – China’s dominant search bot, powering Baidu.
- YandexBot – The crawler for Yandex, Russia’s largest search engine.
- DuckDuckBot – From DuckDuckGo, a privacy-focused search engine that doesn’t track users.
- Sogou Spider – From Sogou, another popular Chinese search engine.
- Exabot – A search bot used by the French search engine Exalead.
- PetalBot – Operated by Huawei for its own search ecosystem.
- SeznamBot – Crawler from the Czech search engine Seznam.
Why they matter: These search engine spiders ensure your pages are indexed and ranked. If blocked, your content won’t appear in search results.
2. SEO Tool Crawlers
These bots are not search engines themselves, but belong to SEO platforms that analyze your site’s performance, backlinks, and keyword data.
- AhrefsBot – Gathers backlink data for the Ahrefs SEO tool.
- SemrushBot – Crawls for Semrush’s keyword and competitor analytics.
- Moz’s Rogerbot – Used by Moz to calculate Domain Authority and crawl links.
- Screaming Frog SEO Spider – Simulates a search engine crawl to audit on-page SEO.
- Majestic-12 Bot – Used by Majestic SEO to map the web and analyze link profiles.
- Dotbot – Crawl tool by Moz/STAT for SERP tracking.
- SEOkicks-Robot – A German backlink crawler for link profile analysis.
Why they matter: These bots support your SEO tools. If you’re using any of these platforms, allowing their bots gives you more accurate data.
3. Social Media Crawlers
These bots fetch link previews and content metadata when your site is shared on social platforms.
- Facebook External Hit (facebookexternalhit) – Fetches title, image, and meta tags for Facebook link previews.
- Twitterbot – Used by X (formerly Twitter) to generate link previews.
- LinkedInBot – Grabs OG/meta tags for LinkedIn shares.
- Slackbot – Fetches previews in Slack messages.
- TelegramBot – Prepares previews for Telegram link shares.
- Discordbot – Extracts site metadata for Discord messages.
Why they matter: These bots don’t index content but improve how your site appears when shared, affecting click-through rates from social platforms.
4. Commercial Bots and Other Indexers
Some bots don’t fit neatly into the categories above but serve various data collection and monitoring purposes.
- UptimeRobot – Monitors site uptime and alerts you of outages.
- PingdomBot – Used for performance and uptime monitoring.
- CCBot – Common Crawl’s bot used for large-scale open web archiving.
- archive.org_bot (Wayback Machine) – Archives your site’s history over time.
- QwantifyBot – Crawler for the Qwant search engine (France-based).
Why they matter: These bots collect performance data or store archives of your site for public use.
5. Suspicious, Spammy, or Malicious Bots to Watch Out For
Not all bots are helpful. Some are designed to scrape your content, attack vulnerabilities, or flood your server with requests. These bots often ignore robots.txt rules and can overload your hosting environment.
Examples of bots to monitor/block:
- MJ12bot (aggressive variants) – Though used by Majestic, it can become resource-intensive.
- BLEXBot – Allegedly a crawler, often flagged as aggressive.
- crawler4j – An open-source crawler framework that can be used for scraping.
- python-requests/urllib bots – Often custom bots coded for scraping.
- SiteAnalyzerBot – Sometimes used to mirror entire websites.
- Spam bots with fake user-agents – Pretend to be Googlebot or Bingbot.
What to do:
- Use tools like Cloudflare, Wordfence (for WordPress), or .htaccess rules to block them.
- Review server logs to identify patterns.
- Consider setting
crawl-delaydirectives or using CAPTCHA for forms.
FAQs About Web Crawlers and User Agents
What is a crawler in SEO?
A crawler (or bot) in SEO is a software program used by search engines to discover, scan, and index web pages. Crawlers like Googlebot analyze page content, metadata, and links to determine ranking in search results.
How can I identify bots visiting my website?
You can identify crawlers through server logs, Google Search Console, or analytics tools. Look for specific user-agents such as Googlebot, Bingbot, or AhrefsBot in access logs.
Should I block some crawlers?
It depends. While major crawlers help your SEO, others might be scraping content or creating server load. Use robots.txt, .htaccess, or a firewall to block or manage unwanted bots.
Is every crawler from a search engine?
No. While many bots belong to search engines, others are run by SEO tools (like Semrush or Ahrefs), social media platforms (like Facebook or Twitter), or uptime monitoring services.
What is a crawler user-agent?
A crawler’s user-agent is a string of text that identifies the bot accessing your site. For example, Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html) indicates that Googlebot is crawling your page.
How To Identify and Track Crawlers on Your Website
You can often tell which bot visited your site by looking at the User-Agent string in your server logs. Each bot has a unique name, like “Googlebot” or “Bingbot.” Learning to recognise these names helps you track which bots are visiting your site.
Server logs are files that record every visit to your website. They show which bots accessed which pages, when they visited, and what they were doing. Reading logs takes some practice, but it’s a great way to understand bot behaviour.
There are also tools to make this easier. Platforms like Cloudflare and Google Search Console show you traffic from bots and help you understand how often they visit. Some tools even warn you if a bot looks suspicious or is causing problems.
Good Bots vs. Bad Bots
Not all bots are created equal. Good bots help your website show up in search results, improve how your content is displayed on social media, or gather SEO data for you. These bots follow rules and don’t try to overload your site.
Bad bots are the opposite. They might steal your content, copy prices from your store, or try to break into your website. They usually ignore rules and can cause slow loading times, which makes your site harder for real visitors to use.
The challenge is to tell them apart. You want the good bots to keep visiting, but block or slow down the bad ones. Knowing the difference helps protect your site while still getting the benefits of being found online.
Leveraging Web Crawlers for SEO Success
Search engines prefer websites that are easy to explore. A good site structure with clear internal links helps crawlers move through your pages and find all your content. This makes it easier for your pages to show up in search results.
You can also manage how bots use their time with a file called robots.txt. This tells them which pages they should or shouldn’t visit, helping you save your crawl budget for the most important parts of your site.
Keeping your content fresh also helps. Bots like websites that are updated often, as it signals that your site is active and worth showing to users. Adding blog posts or updating product pages regularly can improve how often bots return.
Since Google now focuses on mobile-first indexing, your site should load quickly and work well on phones. Page speed and mobile-friendliness are now key signals that bots use to decide your site’s rank.
How To Manage or Block Web Crawlers
You can control crawler behaviour with tools like robots.txt and meta tags. These let you block certain pages from being crawled or tell bots not to index certain parts of your site. It’s a simple but powerful way to guide them.
If you’re dealing with harmful bots, you might need stronger tools. CAPTCHAs, firewalls, and bot blockers can stop bots that are causing trouble. These tools check for signs that a visitor is a human before letting them access your site.
Cloudflare and other services also offer advanced bot management. They can block known bad bots, limit how many times bots can visit, or show alerts when something unusual happens. These tools help keep your site safe without affecting regular visitors.
Recommended Tools for Web Crawler Analysis
1. Screaming Frog SEO Spider
This is a desktop tool that “crawls” your website just like search engines do. It shows which pages are working, which are broken, what your metadata looks like, and where there are SEO problems. It’s like having your own mini Googlebot to scan your site.
2. Google Search Console
A free tool from Google that tells you how Googlebot sees your site. It shows which pages are indexed, if there are crawl errors, how often Googlebot is visiting your site, and what keywords people use to find you. It’s super helpful and easy to use.
3. Ahrefs, Semrush- Crawler List
These are powerful paid tools that also crawl your site on a regular basis. They show your backlinks, rankings, competitor data, and much more. They also alert you to technical issues, helping you fix SEO problems before they affect your traffic.
4. Bot detection APIs and software
Some services help you detect which bots are visiting your site. Some even tell you if the bot is good or bad. Tools like Cloudflare, BotGuard, and Datadome help you control bot access and protect your website from abuse.
Final Thoughts
Web crawlers play a significant role in determining how websites are perceived online. If you ignore them, you might miss out on traffic, search visibility, and key SEO improvements. Paying attention to how they work can make a big difference.
By tracking bot visits and learning to distinguish between legitimate and malicious traffic, you can make more informed decisions for your website. You’ll keep your site faster, safer, and more attractive to search engines.
The best part is that you don’t need to be a tech expert to do this. With the right tools and some basic understanding, you can start improving your site today. Utilise crawler data to enhance your SEO, safeguard your site, and stay ahead of your competitors.
Understanding which web crawlers access your site gives you the power to fine-tune SEO, enhance performance, and secure sensitive content. Use this crawler list as a reference for identifying and managing both helpful and potentially harmful bots. Whether you’re optimizing for Google, checking for duplicate content scrapers, or simply improving your site’s speed, keeping an eye on crawler activity is a smart part of modern WordPress site management.
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