What Is an ISP?

What Does an ISP Do?

An Internet Service Provider (ISP) is a company that provides access to the internet. ISPs maintain the physical infrastructure (cables, fiber optics, cell towers, satellite dishes) and the network equipment necessary to connect your device to the global internet. When you connect to the internet, your ISP:

• Assigns your device an IP address
• Routes your traffic to and from the internet
• Provides DNS resolution (translating domain names to IP addresses)
• May filter or manage traffic according to their policies

Types of ISPs

ISPs come in several forms:

• DSL (Digital Subscriber Line) — uses existing telephone lines, widely available but slower than fiber
• Cable — uses coaxial cable television infrastructure, offers good speeds shared among neighborhood users
• Fiber optic — uses thin glass cables to transmit data as light, offering the fastest speeds and lowest latency
• Wireless/Fixed Wireless — uses radio signals to provide internet, common in rural areas
• Satellite — provides internet via orbiting satellites, available almost anywhere but with higher latency
• Mobile/Cellular — provides internet through 4G/LTE or 5G cell networks

What Can Your ISP See?

Your ISP is in a unique position to observe your online activity. Depending on their infrastructure and your usage of encryption, they can potentially see:

• Which websites you visit (through DNS queries and SNI in TLS handshakes)
• The amount of data you transfer
• The times you're active online
• Your IP address and the IP addresses you connect to

However, with HTTPS encryption, your ISP cannot see the specific pages you view or the content of your communications. They can see which domain you're connecting to, but not what you're doing on that domain. Using a VPN, encrypted DNS (DoH/DoT), and HTTPS significantly limits what your ISP can observe.

Finding Your ISP

You can identify your ISP using any IP lookup tool. Our IP Tester homepage displays your ISP information as part of the connection details. If you're curious about what network information is associated with your IP, try our IP Lookup tool.