Network Tools

When a website will not load, email stops arriving or a server seems slow, the first job is to find out where the problem sits. These tools answer the basic questions from outside your own network: is the site up, what IP address does the name resolve to, which mail servers handle the domain, and is the port you need actually open.

18 tools

Website Status Checker

Check whether a website is up and reachable, or down for everyone.

Ping

Measure how long a server takes to respond, to spot slow or unreachable hosts.

IP to Hostname

Reverse-lookup an IP address to find the hostname it points back to.

Hostname to IP

Resolve a domain or hostname to all the IPv4 and IPv6 addresses it currently points at.

IP Address Lookup

Look up any IP address: location, ISP, organisation, ASN and time zone. Leave it empty for your own IP.

MX Lookup

See which mail servers accept email for a domain, in priority order.

SPF, DKIM & DMARC Checker

Check a domain's email authentication records and find out why its mail goes to spam.

User Agent Finder

Show your browser's full user agent string, plus the browser, OS and device it describes.

What's My IP

See the public IP address that websites see when you connect.

DNS Lookup

Fetch a domain's A, AAAA, NS, MX, TXT and SOA records in one go.

Open Port Checker

Test whether a TCP port on a host is open and accepting connections.

IP Subnet Calculator

Work out the network, broadcast address, mask and usable host range for any subnet.

DNS Propagation Checker

Check a domain's DNS records on 20 public resolvers worldwide and its own nameservers at once.

ASN Lookup

Look up an autonomous system (AS number), or the ASN behind an IP or domain: owner, IP ranges and peers.

IP Blacklist Checker

Check an IP address or server against 19 spam and abuse blacklists (DNSBLs) at once.

Email Blacklist Checker

Check a domain and its mail servers against domain and IP blacklists to find email delivery problems.

Traceroute Online

Run a traceroute or MTR to any domain or IP from servers around the world and see every hop, its location and delay.

Global Ping Test

Ping a website or server from up to 15 locations around the world at once and compare response times and packet loss.

A common job

Find out why a site is down

Confirm it is down for everyone, check where the name points, rule out the certificate, then trace the route.

Guides: HTTP status codes explained SSL certificate errors

More about Network Tools

Start with the Website Status Checker or Ping to confirm whether a host responds at all. Use DNS Lookup and Hostname to IP to see where a domain points, and MX Lookup or the SPF, DKIM & DMARC Checker when mail is the problem, and the Open Port Checker when a service will not accept connections. IP Information and IP to Hostname tell you who is behind an address, the Hosting Checker shows which company hosts a website, and the IP Subnet Calculator helps when you are planning or reading network ranges.

After moving a site or changing records, the DNS Propagation Checker asks 20 resolvers around the world at once, so you can see who already has the new answer. The IP Blacklist Checker and Email Blacklist Checker find out whether a server or domain is on a spam list, and the ASN Lookup shows which network owns an address and the IP ranges it announces.

To see a site from the rest of the world, the Global Ping Test pings it from up to 15 countries at once and Traceroute Online shows every hop from a location you choose, with MTR packet-loss statistics.