# What is URL Filtering?

> URL filtering is the policy-based evaluation of a requested web address or related destination information to allow, block, warn, redirect, isolate, or record access.

- Canonical URL: https://yellowcube.eu/glossary/uniform-resource-locator-filtering/
- Publisher: Yellow Cube
- Language: en
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## Content

A decision may use the full Uniform Resource Locator (URL), domain, hostname, path, category, reputation, age, ownership, or observed campaign links, depending on what the enforcement point can see.

Filtering can run in a browser, endpoint agent, proxy, secure web gateway, or domain-name control. With encrypted web traffic, an intermediary may see only the domain unless it terminates Transport Layer Security (TLS), while Domain Name System (DNS) filtering generally acts on domains rather than full URLs.

### Key points

- **Policy design:** Use categories and reputation as inputs to documented, risk-based rules, with narrower exceptions for legitimate sites that are misclassified or newly established.
- **Context and action:** Consider user, device, destination, request method, and business purpose; warning, isolation, or restricted access may be more suitable than a universal block.
- **Operations:** Record decision reasons, review overrides, refresh threat and category data, and protect browsing records because they can reveal sensitive interests and activity.
- **Important limitation:** Classifications become stale, shared hosting mixes unrelated services, redirects obscure final destinations, and newly created sites lack history. An allowed URL is not a safety verdict, and a blocked URL is not proof of maliciousness.

### Related terms

[Content filtering](<https://yellowcube.eu/glossary/content-filtering/>) · [Secure web gateway (SWG)](<https://yellowcube.eu/glossary/secure-web-gateway/>) · [Domain Name System (DNS) security](<https://yellowcube.eu/glossary/domain-name-system-security/>) · [Phishing](<https://yellowcube.eu/glossary/phishing/>) · [Proxy server](<https://yellowcube.eu/glossary/proxy-server/>)

### Sources

[NIST SP 800-215, Guide to a Secure Enterprise Network Landscape](https://csrc.nist.gov/pubs/sp/800/215/final) · [UK NCSC, What to do before building a ZTNA architecture](https://www.ncsc.gov.uk/collection/zero-trust/zero-trust-network-access-ztna/what-to-do-before-building-a-ztna-architecture) · [UK NCSC, Zero trust migration: How will I know if I can remove my VPN?](https://www.ncsc.gov.uk/collection/zero-trust/implementing-zt/zero-trust-migration-how-know-remove-vpn)

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