CAT KARAT PACKET BUILDER ·
Build the exact packet. Send it in a few clicks.
A visual packet builder for engineers, students, and test labs — with raw editing, multiple streams, traffic presets, PCAP import, and command-line automation.
Completely free · personal, educational, and commercial use · Windows and Linux
01 / VISUAL PACKET FLOW
Compose the stack without writing code.
Select protocols, set individual fields, inspect the resulting bytes, and transmit through a chosen interface. KARAT supports Ethernet, VLAN, ARP, IPv4, IPv6, UDP, TCP, ICMP, DNS, and additional protocols while keeping raw editing available at every step.
MULTIPLE STREAMS
One interface, several independent traffic flows.
Configure separate streams, counters, packet sizes, rates, and protocol combinations. Use the visual controls for interactive work or run a fixed number of packets from the CLI and exit cleanly for automation.
- Import from PCAP or a Wireshark, tcpdump, or xxd hex dump
- Raw hex and protocol-field editing
- Packet Player with capture validation
- Reusable scripted presets
TRAFFIC PRESETS
Start with a useful test, then change anything.
Load application mixes and laboratory profiles without rebuilding every packet by hand. Any preset can also be applied from a script.
{ "preset": "tcp_syn" }
FREE MEANS FREE
No trial clock. No feature paywall. No commercial-use restriction.
Cat KARAT is free for personal projects, teaching, laboratory work, and commercial testing on Windows and Linux.
DOWNLOAD OPTIONS →DOWNLOAD DETAILS
System requirements and file integrity.
KARAT is a free single-edition product. Live sending and capture require packet-capture support; file-building mode does not.
Requirements
- Windows
- Windows 10/11 64-bit; Npcap for interface listing, live send, and capture
- Linux
- x86-64; Debian/Ubuntu/Mint, Fedora/RHEL/Rocky, or tar.gz; packed binary with no system Perl requirement; libpcap and X11/font libraries are required
- Memory
- 256 MB or more recommended
- Display
- 1000×830 or larger
- Privileges
- Administrator/root or network capabilities may be needed for live I/O; output and dry-run modes do not need them
Packages and SHA-256
| Package | Approx. size | SHA-256 |
|---|---|---|
| Windows exe | 13.3 MB | 3db6bf13cef1fa8cdb933abb29fb7579dbbf6274e0ae2de0e62f3a7fdbd13284 |
| Debian / Ubuntu .deb | 4.8 MB | 8e2f90fa06feb04f49e96603e4cbb48d916397f706de9b7400a72d26231a12fa |
| Fedora / RHEL .rpm | 5.3 MB | 623b10dbde8dc57b6f28922f6bfe4858ee55896d31b162bf444252caf5cf1c87 |
| Linux tar.gz | 5.3 MB | 5ac9764f1599a631d7a6d0219abe1cf4bc6889cce6f7d193ef0d8c7c2e3901fb |
The complete license text supplied with the package governs use. Separate release notes were not supplied for this page. Questions: undefinable@yandex.com.
SUPPORT KARAT
Help keep a professional packet builder free.
KARAT can be downloaded and used without payment. If it saves you time or helps your lab, an optional donation can support maintenance, protocol updates, testing, and documentation.
Donating is optional and does not unlock hidden features.
READY TO BUILD
From an empty frame to traffic on the wire.
Download the current release, watch the short demonstration, and start with a preset or a packet captured in your own lab.