What Is a Web Crawler? (Googlebot, Bingbot Explained)

Every time you search for something on Google or Bing and get an answer in under a second, you are seeing the end result of a quiet, constant process that runs 24 hours a day across the entire internet. That process is web crawling, and the programs doing it are called web crawlers. If you own a website, run a business online, or just want to understand how search actually works, knowing what a web crawler is and how Googlebot and Bingbot operate is one of the most useful pieces of knowledge you can have. This guide explains exactly what a web crawler is, how the major ones work, the difference between Googlebot and Bingbot, and why all of this directly affects whether your website shows up in search results at all.

A web crawler is an automated program (also called a spider or bot) that systematically browses the internet, following links from page to page to discover and collect content. Search engines use crawlers to build their index, which is the database they pull results from. Googlebot is Google’s crawler and the most active bot on the internet. Bingbot is Microsoft’s crawler, which also powers Yahoo, DuckDuckGo, and Copilot. If a crawler cannot access your pages, those pages cannot appear in search results, which is why crawling is the foundation of all SEO.

What Is a Web Crawler in Simple Terms?

A web crawler is an automated program that browses the internet on its own, jumping from link to link to discover and read web pages. It is also called a spider, a bot, or a crawler, and all three terms mean the same thing.

Imagine a tireless reader who starts on one web page, reads everything on it, then clicks every link on that page to reach new pages, reads those, clicks their links, and keeps going forever across billions of pages. That is essentially what a web crawler does. It does not stop, it does not sleep, and it never runs out of pages to visit because the internet keeps growing.

Web crawlers are the first step in how a search engine works. Before any page can show up in search results, a crawler has to find it, read it, and pass it along to be stored. This is part of the larger system explained in the breakdown of how a search engine works, where crawling is stage one of a three stage process that ends with ranked search results.

How a Web Crawler Actually Works

The crawling process follows a clear sequence, even though it happens at a massive scale across the entire web.

Step 1: Start with a list of known URLs. Crawlers begin with a list of web addresses they already know about, often from previous crawls and submitted sitemaps. This starting list is sometimes called the “seed.”

Step 2: Visit and read each page. The crawler downloads the page content: the text, the HTML structure, the links, the images, and the metadata. Modern crawlers like Googlebot also render JavaScript, which means they can read content that only loads after a page’s scripts run, the same way a browser does.

Step 3: Follow the links. The crawler extracts every link on the page and adds those new URLs to its list of pages to visit. This is how crawlers discover new content without anyone manually telling them it exists.

Step 4: Send the data to the index. Everything the crawler collects gets passed to the search engine’s index, which is the giant database that powers search results.

Step 5: Repeat on a schedule. Crawlers revisit pages on a schedule based on how often the content changes. A news homepage might get crawled many times a day. A static “about us” page might get crawled once every few weeks.

Website owners can guide this process. A robots.txt file tells crawlers which areas of a site to skip, and an XML sitemap tells crawlers which pages exist and should be prioritized. Both are essential tools for managing how crawlers interact with your site.

Googlebot Explained: Google’s Crawler

Googlebot is the web crawler used by Google, and it is the most active bot on the entire internet. It is responsible for discovering and indexing the billions of pages that show up in Google Search, Google Images, and Google News.

Key things to know about Googlebot:

It comes in two main versions. Googlebot Desktop simulates a user browsing on a computer, and Googlebot Smartphone simulates a user on a mobile device. Since Google moved to mobile first indexing, the smartphone crawler is the primary one that determines how your site ranks.

It renders JavaScript. Unlike older crawlers, Googlebot processes JavaScript heavy pages, which means it can read content that loads dynamically. This matters a lot for modern websites built on frameworks like React or Vue.

It respects crawl directives. Googlebot follows the rules in your robots.txt file and respects crawl rate settings you configure in Google Search Console.

It assigns a crawl budget. Google decides how many pages of your site it will crawl in a given period based on your site’s authority and how fast your server responds. More on this below.

You can monitor exactly how Googlebot interacts with your site using Google Search Console, which shows crawl stats, indexing status, and any pages where the crawler hit problems.

Bingbot Explained: Microsoft’s Crawler

Bingbot is Microsoft’s web crawler, deployed in 2010 to power the Bing search engine. It performs the same core function as Googlebot, discovering and indexing web content, but it serves a broader ecosystem than most people realize.

Key things to know about Bingbot:

It powers more than just Bing. Bingbot’s index feeds Bing, Yahoo Search (which is powered by Bing), DuckDuckGo, and Microsoft’s Copilot AI search. Optimizing for Bingbot means visibility across several platforms at once.

It supports IndexNow. This is a major advantage Bingbot has over Googlebot. IndexNow is a protocol that lets you instantly notify Bing whenever you publish or update content, instead of waiting for the next scheduled crawl. This means faster indexing on Bing powered platforms.

It prioritizes mobile friendly pages. Like Google, Bing weighs mobile usability heavily in how it crawls and ranks.

It has specialized sub crawlers. These include BingPreview (for page previews), AdIdxBot (for Bing Ads landing pages), and MicrosoftPreview (for previews in Teams and Office).

Bing provides its own free toolset called Bing Webmaster Tools, which works like Google Search Console for monitoring how Bingbot crawls your site.

Googlebot vs Bingbot: The Key Differences

Both crawlers do the same fundamental job, but the differences matter for SEO. Here is the clean comparison.

The practical takeaway: most site owners focus on Googlebot because of Google’s dominant market share, but ignoring Bingbot is a mistake. Bingbot visibility gets you onto Bing, Yahoo, DuckDuckGo, and Copilot all at once, and IndexNow makes Bing indexing faster than Google in many cases.

The Rise of AI Crawlers (GPTBot, Claudebot, and More)

This is the part almost no older article covers, and it is the biggest shift in the crawler world in 2026. Search engine crawlers are no longer the only bots reading your site. AI companies now run their own crawlers to collect training data and to fetch live information for their assistants.

The major AI crawlers in 2026:

• GPTBot (OpenAI) collects public web content to help train and inform ChatGPT.
• ChatGPT-User (OpenAI) fetches live pages when a user asks ChatGPT something that needs current information.
• Claudebot (Anthropic) crawls content for Claude.
• Google-Extended lets you control whether your content is used for Google’s AI products separately from normal Googlebot crawling.
• Meta-ExternalAgent (Meta) and Bytespider (ByteDance, TikTok’s parent) also crawl actively.

This creates a real decision for website owners: should you allow AI crawlers or block them? Blocking GPTBot and Claudebot keeps your content out of AI training data, which some publishers prefer. But allowing them can mean your brand gets cited inside ChatGPT and Claude answers, which is becoming a valuable visibility channel. There is no universal right answer, and the decision depends on your business goals. This is exactly the kind of strategic call covered in the answer engine optimization guide, which walks through how to stay visible inside AI assistant answers in 2026.

What Is Crawl Budget and Why It Matters

Crawl budget is one of the most misunderstood concepts in SEO, and getting it right can be the difference between your pages being indexed quickly or being ignored for weeks.

Crawl budget is the number of pages a search engine crawler will crawl on your site within a given timeframe. It is a limited resource, and search engines assign it based on two things: how authoritative your site is (crawl demand) and how fast and stable your server is (crawl rate limit).

Why it matters: if you have a large website with thousands of pages but a small crawl budget, the crawler may never reach some of your important pages, which means they never get indexed and never rank. This is a common problem for large e-commerce sites and content heavy blogs.

How to make the most of your crawl budget:

1. Fix broken links and redirect chains. Every dead link wastes the crawl budget.
2. Keep your site fast. A faster server lets crawlers visit more pages in the same time window.
3. Remove or block low value pages. Thin tag pages, duplicate content, and filter URLs eat budget without adding value.
4. Submit a clean XML sitemap. This points crawlers directly to the pages that matter.
5. Use internal linking well. Pages that are linked to from many other pages get crawled more often.

For small sites under a few hundred pages, crawl budget is rarely a concern. For large sites, it becomes a serious optimization priority.

How to Control What Crawlers Access on Your Site

You have more control over crawlers than most people realize. Here are the main tools.

robots.txt. A simple text file in your site’s root directory that tells crawlers which pages or folders to skip. For example, you can block crawlers from your admin pages or internal search results. Be careful, because blocking the wrong thing can remove important pages from search.

Meta robots tags. Added to individual pages, these tell crawlers whether to index a page (index or noindex) and whether to follow its links (follow or nofollow). This gives you page level control that robots.txt cannot.

Canonical tags. These tell crawlers which version of a duplicate or similar page is the “main” one to index, which prevents duplicate content issues.

XML sitemaps. These actively guide crawlers to your important pages and tell them how often each page changes.

Crawl rate settings. In Google Search Console and Bing Webmaster Tools, you can adjust how aggressively the crawlers visit your site, which is useful if crawling is slowing down your server.

Getting these settings right is foundational technical SEO, and getting them wrong is one of the most common reasons websites fail to rank despite having good content.

Yes, breaking this section into subheadings improves readability and SEO. Google’s algorithm reads subheadings as content structure signals, and readers scan rather than read, so subheadings keep them on the page longer. Here is the section restructured with clean subheadings.

Why Web Crawlers Matter for Your Business

Understanding web crawlers is not just technical trivia. It directly affects whether your business gets found online.

The Chain Reaction: No Crawl Means No Traffic

If crawlers cannot access your pages, those pages will not be indexed. And without indexing, your site cannot rank or generate organic traffic. The entire chain of search visibility starts with crawling, which means crawl issues are some of the most damaging and most overlooked problems in SEO.

A Real Example: One Line That Collapsed a Catalog

We have worked with businesses whose traffic was stuck for months not because their content was bad, but because a single misconfigured robots.txt line was blocking Googlebot from their most important pages. In one case, an e-commerce client had accidentally blocked their entire product catalog from being crawled after a site migration. Their rankings had collapsed and no one could figure out why. Fixing the crawl directive restored their indexed pages within three weeks, and their organic traffic recovered to above pre migration levels within two months.

Why Crawl Health Should Be Your First Audit

This is why crawl health is one of the first things to audit when a site is underperforming. If your website is not getting the search traffic you expect, the SEO team at Leemjaz runs technical crawl audits that catch exactly these kinds of issues, often finding indexing problems that have been quietly costing businesses traffic for months.

Frequently Asked Questions

1. What is the difference between a web crawler and a web scraper?

A web crawler discovers and indexes pages by following links, usually for search engines. A web scraper extracts specific data from pages, often for a single purpose like price monitoring or data collection. Crawlers map and index broadly, while scrapers target and pull specific information. Many scrapers are unauthorized, while major crawlers like Googlebot are welcomed.

2. Is Googlebot the same as Google Chrome?

No. Google Chrome is a web browser that people use to view websites. Googlebot is an automated crawler that reads websites for indexing. They are different tools, though Googlebot does use the same underlying rendering engine as Chrome to process pages, which is why it can read JavaScript content the way a browser does.

3. How do I know if a web crawler is visiting my site?

You can see crawler activity in your server logs or, more easily, in Google Search Console (Crawl Stats report) and Bing Webmaster Tools. These show which pages were crawled, how often, and whether the crawler hit any errors. Every crawler also identifies itself with a unique user agent string in your logs.

4. Should I block AI crawlers like GPTBot and Claudebot?

It depends on your goals. Blocking them keeps your content out of AI training data, which some publishers prefer. Allowing them can get your brand cited inside ChatGPT and Claude answers, which is a growing visibility channel. There is no universal right answer, so weigh whether AI visibility or content protection matters more for your business.

5. Can a web crawler hurt my website?

Legitimate search crawlers like Googlebot and Bingbot do not hurt your site. However, aggressive or fake crawlers can overload your server and slow it down. You can manage this by setting crawl rate limits, blocking known bad bots in robots.txt, and using a security service to filter malicious bot traffic.

6. Why are some of my pages not being crawled?

Common reasons include a robots.txt rule blocking them, a noindex tag on the page, the page being too deep in your site structure with few internal links, a slow server limiting crawl budget, or the page simply being too new. Checking Google Search Console’s coverage report usually reveals the exact cause.

Conclusion

A web crawler is the starting point of everything that happens in search. Googlebot, Bingbot, and the growing list of AI crawlers like GPTBot and Claudebot constantly read the web, deciding what gets discovered and what stays invisible. For website owners and businesses, this is not abstract technology, it is the foundation of whether customers find you online at all. The sites that win in search make crawling easy: clean site structure, fast servers, smart robots.txt rules, and clear sitemaps. The sites that struggle usually have quiet crawl issues nobody noticed. Understanding how crawlers work is the first step to making sure your pages get the visibility they deserve, and it builds the technical foundation that everything else in SEO sits on.