What is URL Filtering?

How URL-Based Web Filtering Works

URL filtering controls access to specific web pages based on their URLs. Unlike DNS filtering which blocks entire domains, URL filtering can make granular decisions about individual pages. This article explains how it works and how it compares to DNS-based approaches.

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Step 1: How URL Filtering Works

URL filtering inspects the full URL of a web request — not just the domain name — and makes an allow or block decision based on categorization. For example, a URL filter could allow access to reddit.com but block specific subreddits containing inappropriate content.

URL filtering typically requires a proxy or agent that can inspect the full URL path of HTTP and HTTPS requests. This means it operates at a different network layer than DNS filtering and requires more infrastructure.

Step 2: URL Filtering vs DNS Filtering

Feature URL Filtering DNS Filtering
GranularityIndividual pagesEntire domain
DeploymentRequires proxy, agent, or firewallSimple DNS setting change
PerformanceHigher latency (inspects full requests)Minimal latency (DNS lookup only)
HTTPS TrafficRequires TLS inspectionWorks with encrypted traffic natively
Device SupportRequires agent or network proxyWorks on any device that uses DNS
CostGenerally higherGenerally lower

Step 3: Common URL Filtering Methods

Proxy-Based Filtering

A web proxy sits between users and the internet, inspecting every request. It provides the most granular control but adds latency and complexity.

Agent-Based Filtering

Software agents on individual devices intercept web requests and apply filtering rules. Works for remote users but requires software management.

Firewall-Based Filtering

Next-generation firewalls (NGFWs) can perform URL filtering as part of traffic inspection. Requires capable hardware and TLS inspection for HTTPS.

Step 4: Choosing the Right Approach

For most families, schools, and small to mid-size organizations, DNS filtering provides the best balance of effectiveness, simplicity, and cost. It blocks harmful domains without deploying proxies or agents.

URL filtering is more appropriate for large enterprises that need page-level granularity and already have proxy or NGFW infrastructure.

CleanBrowsing provides DNS-based content filtering that is easy to deploy and effective. Visit our Getting Started page to set up filtering in minutes, or explore our paid plans for advanced features.

DNS filtering: simple, effective, affordable.

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