Domain vs URL vs IP Address: What's the Difference?

What DNS Resolvers Actually See — and Why It Matters

Domains, URLs, and IP addresses are often used interchangeably, but they serve very different purposes. Understanding their distinctions is key to understanding how DNS filtering works — and what it can and cannot do.

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Step 1: What is a Domain?

A domain is a human-readable address used to identify a website or online service. Instead of remembering a long numerical IP address like 93.184.216.34, you can simply type example.com into your browser. Domains exist to make the internet accessible and navigable for everyday users.

Domains are structured in a hierarchy of levels. At the highest level is the Top-Level Domain (TLD) — the suffix like .com, .org, or .net. Below that is the second-level domain, which is the name you register (e.g., example in example.com). You can also add subdomains in front of the second-level domain, such as www.example.com or mail.example.com. Together, these components form what is known as a Fully Qualified Domain Name (FQDN).

When you enter a domain into your browser, your device sends a query to a DNS resolver. The resolver translates the domain name into the corresponding IP address so your browser can establish a connection to the correct server. This translation process — called DNS resolution — is the foundation of how the internet works. Without DNS, you would need to memorize IP addresses for every website you visit.

It is important to understand that DNS resolvers work with domains — specifically FQDNs. They do not process full URLs, nor do they handle direct IP connections. This distinction is critical when evaluating what DNS filtering can accomplish.

Step 2: What is a URL?

A URL (Uniform Resource Locator) is the complete web address you see in your browser's address bar. While a domain identifies a website, a URL identifies a specific resource on that website — a particular page, file, or section.

A URL is composed of several parts:

  • Scheme: The protocol used, such as https:// or http://. This tells the browser how to connect to the server.
  • Domain: The hostname, such as www.example.com. This is the portion that DNS resolvers handle.
  • Path: The specific page or resource on the server, such as /page or /blog/article-title.
  • Query String: Parameters passed to the server, such as ?id=123&category=news. These often control what content is displayed.
  • Fragment: An anchor within the page, such as #section2. This tells the browser to scroll to a specific part of the page.

For example, in the URL https://www.example.com/page?id=123#section, the domain is www.example.com, the path is /page, the query string is ?id=123, and the fragment is #section.

This distinction matters because DNS resolvers only handle the domain portion of a URL. When your browser processes a URL, it first extracts the domain and queries the DNS resolver for the IP address. The path, query string, and fragment are then sent directly to the web server over HTTP or HTTPS — the DNS resolver never sees them.

This means DNS filtering cannot block individual pages on a website. It can block example.com entirely, but it cannot allow example.com/safe-page while blocking example.com/unsafe-page. For that level of granularity, you need URL filtering through a proxy or next-generation firewall.

Step 3: What is an IP Address?

An IP (Internet Protocol) address is a numerical identifier assigned to every device connected to a network. IP addresses are what computers actually use to communicate with each other — domains are just a human-friendly layer on top.

There are two versions of IP addresses in use today:

  • IPv4: The original format, using four groups of numbers separated by dots (e.g., 192.168.1.1 or 93.184.216.34). IPv4 supports approximately 4.3 billion unique addresses, which are now nearly exhausted.
  • IPv6: The newer format, using eight groups of hexadecimal characters separated by colons (e.g., 2001:0db8:85a3::8a2e:0370:7334). IPv6 provides a virtually unlimited address space and is increasingly adopted worldwide.

Every website and online service has at least one IP address. When you type a domain into your browser, DNS resolves it to an IP address, and your browser connects to that IP. However, if you access a site by entering its IP address directly into the browser (e.g., http://93.184.216.34), the DNS resolver is bypassed entirely. No DNS query is made, so the resolver never sees the request and has no opportunity to filter it.

This is one of the fundamental limitations of DNS-based filtering. Applications, malware, and knowledgeable users can connect directly to IP addresses to circumvent DNS controls. To block IP-based connections, you need firewall rules that operate at the network layer rather than the DNS layer.

Understanding the difference between domains and IP addresses is essential for building a comprehensive network security strategy. DNS filtering and firewall rules serve complementary roles — one controls domain-level access, the other controls IP-level access.

Step 4: Why This Matters for DNS Filtering

Now that you understand the differences between domains, URLs, and IP addresses, you can see why DNS filtering operates the way it does — and where its boundaries lie.

  • DNS filtering works at the domain level. It can block entire domains (e.g., all of example.com) based on category, custom rules, or threat intelligence. This is its core strength — it is simple, fast, and covers every device on the network.
  • DNS filtering cannot filter individual pages. Because DNS only sees the domain, it cannot distinguish between example.com/safe-page and example.com/unsafe-page. For page-level control, you need URL filtering with a web proxy that inspects the full URL.
  • DNS filtering cannot block IP-based connections. When a user or application connects directly to an IP address, DNS is bypassed entirely. To block IP-based traffic, you need firewall rules at the router or device level.

For most use cases — families protecting children, schools meeting compliance requirements, businesses blocking malware and inappropriate content — DNS filtering provides the best balance of simplicity, coverage, and protection. It requires no software installation, works across all devices on the network, and can be deployed in minutes by changing a single DNS setting on your router.

When more granular control is needed, DNS filtering should be used as the foundation, complemented by URL filtering proxies for page-level inspection and firewall rules for IP-level blocking. These layers work together to provide comprehensive network protection.

CleanBrowsing provides DNS filtering that covers the most common use cases out of the box, including category-based blocking, custom domain rules, and automatic SafeSearch enforcement. For most networks, it is all you need to get started.

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