Glossary · Internet & Web

ISP (Internet Service Provider)

An ISP is a company that provides internet access to homes and businesses, assigning IP addresses and routing traffic to the wider internet.

Updated October 6, 2026

An ISP (Internet Service Provider) is an organization that sells internet connectivity, such as broadband, fiber, cable or mobile data. It connects customers to the rest of the internet and usually assigns them an IP address.

Why it matters

Your ISP affects speed, reliability and which DNS resolver you use by default. When a site is reachable for some people but not others, the problem is sometimes a routing or DNS issue inside a particular ISP, which is why checking from several networks is useful.

Example

If a website loads on mobile data but not on home broadband, the home ISP's DNS or routing may be at fault. Switching the device to a public resolver or testing from another location helps narrow it down.

Common mistakes

  • Blaming the website when the local ISP has an outage.
  • Assuming your public IP is permanent; many ISPs change it periodically.
  • Ignoring that ISPs can block or throttle certain sites in some regions.

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