Start learning

Network tools that run in your browser

The lookups you would normally open a terminal for, plus real ping, traceroute and MTR from a worldwide probe network. Each one links back to the lesson that explains what you are seeing.

17 tools · free · no account Every card says whether it runs locally, looks something up, or uses a real probe

Most used

The four lookups people open most, one click from anywhere.

4 tools

Live tool · runs in this page

Subnet Calculator

Runs locally

Network, mask, broadcast and host range from any CIDR address. Type one below: this is the calculator itself, not a picture of it.

subnet.calcruns locally
Open the full calculator
Live lookup DNS Lookup A, AAAA, MX, TXT and NS records with TTLs, plus who registered the domain. A · AAAA · MX · TXT · NS Open tool Runs locally MAC / OUI Lookup The first three bytes of a MAC address name the company that made the device. B8:27:EB → Raspberry Pi Foundation Open tool Live lookup ASN Lookup Who operates an autonomous system, where it is registered, and what it announces. AS13335 → Cloudflare, Inc. Open tool

Math & addressing

Addressing arithmetic, answered as you type.

3 tools
Runs locally IPv6 Subnet Calculator Expand or compress any IPv6 address, find its prefix range and type, and count the /64s inside. 2001:db8::/48 → 65,536 × /64 Open tool Runs locally IP Class Finder Class A–E, default mask, and public or private: live as you type. 10.0.0.5 → Class A · private Open tool Runs locally Wildcard Mask Turn any prefix into the inverse mask ACLs and OSPF want, with a copy-ready line. /26 → 0.0.0.63 Open tool

Syntax & conversion

Config lines and number bases, converted for you.

2 tools
Runs locally CLI Config Generator ACL, OSPF and VLAN snippets for Cisco, Junos and EOS, each line explained. Cisco IOS · Junos · EOS Open tool Runs locally Hex · Dec · Bin Type in any base and the others update instantly: MAC bytes and masks decoded. 0xC0 = 192 = 1100 0000 Open tool

Diagnostics & visualization

See inside a packet, along a path, and into your own connection.

4 tools
Runs locally Capture (pcap) Reader Open a .pcap or .pcapng in the browser and read it Wireshark-style: packet list and decoded layers. TCP 51514 → 443 [SYN] Open tool Runs locally Packet Inspector A colour-coded IPv4 header with TCP, UDP or ICMP behind it, byte by byte. IPv4 → TCP · UDP · ICMP Open tool Simulation Hop Visualizer A traceroute you can study: hops light up, one times out, and it explains why. * * * Request timed out. Open tool Runs locally What’s My IP What your browser exposes about your device and connection. browser · device · connection Open tool

Live network tests

A browser cannot send ICMP, so these four run on the free Globalping probe network and show you exactly what a real probe returned. About Globalping.

4 tools
Real probe Ping Real echo requests from a probe you choose, with the round-trip times it measured. ICMP echo · rtt min / avg / max Open tool Real probe Traceroute Every hop between a real probe and your target: the live twin of the simulator. hop · address · rtt Open tool Real probe MTR Report Traceroute and ping combined, so the hop that is dropping packets stops hiding. Loss% · Avg · Best · Wrst Open tool Real probe HTTP Server Test Status code, certificate, and a DNS, TCP, TLS and first-byte timing breakdown. status · TLS · timings Open tool

Pick by problem

Not sure which tool? Start from what is wrong

Most people arrive with a symptom, not a tool name. Each one below lists the tools in the order you would reach for them.

  1. A website will not load

    Does the name resolve, does the host answer, and what does the server itself say?

    1. DNS Lookup
    2. Ping
    3. HTTP Server Test

  2. The connection is slow or dropping

    Find the hop where it goes wrong, then check whether that hop is losing packets.

    1. Traceroute
    2. MTR Report
    3. Ping

  3. Planning addresses for a network

    Size the blocks, check the class and scope, and write the masks your ACLs need.

    1. Subnet Calculator
    2. IP Class Finder
    3. Wildcard Mask

  4. An unknown device is on the network

    Identify the maker from its MAC address, then compare it with what your own device shows.

    1. MAC / OUI Lookup
    2. What’s My IP

  5. Writing an ACL or router config

    Generate the lines, then check the wildcard and the block they match.

    1. CLI Config Generator
    2. Wildcard Mask
    3. Subnet Calculator

  6. Learning how a packet is built

    Read a header byte by byte, convert the fields, then watch a path hop by hop.

    1. Packet Inspector
    2. Hex · Dec · Bin
    3. Hop Visualizer
Tools give you an answer Labs make you do the work Wire a cable, order a firewall, find the fault in a broken network: 6 labs, all in your browser. Browse the labs