Welcome to IO Ninja
Your One-Stop Terminal Emulator, Protocol Analyzer & IO Monitor

IO Ninja is a professional all-in-one terminal emulator, sniffer, and protocol analyzer. It runs natively on Windows, Linux, and macOS.

IO Ninja is highly modular and has plugins for most transports and protocols you might come across — network (TCP, UDP, SSL, SSH, WebSockets, etc.), serial (RS-232, RS-485, I2C, SPI, Modbus RTU, etc.), and others (named & anonymous pipes, USB endpoints, J-Link RTT, etc.). IO Ninja is scriptable and allows you to generate packets programmatically, react to incoming packets and other IO events, and create non-standard protocol analyzers.

IO Ninja is your swiss-army knife for debugging communications and a must-have tool for network security experts, system administrators, and all developers who deal with network programming in their line of work.

User rating:  4.7
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IO Ninja Is Used At


IO Ninja 5.6.0 is out!

Major release

  • New syntax constructs dylayout and dyfield for describing dynamic layouts (i.e., data structures defined at runtime)
  • Major improvements in the Packet Template engine — dynamic packet structures, byte-range colorization, support for bitflag enum fields, etc.
  • New Modbus Analyzer plugin based on the new dynamic layout engine
  • New Protocol Analyzer Plugin Wizard for creating your own protocol analyzers — all you have to do is redefine the packet layout function!
  • New in-app scripting pretransmit entry point for the on-the-fly encoding and other modifications of outbound packets
  • Standalone *.njlog logs can create toolbars now (e.g., logs created by Pcap Sniffer and Ethernet Tap now have filtering and export-to-pcap controls)
  • Numerous critical fixes in various modules

See also

Hardware Sniffers

We proudly present you the three hardware sniffers for IO Ninja. These devices are simple yet functional and convenient sniffers for asynchronous serial links (RS232, RS422, RS485, TTL-level UART), synchronous serial links (I2C, SPI), and Ethernet.

Why You Should Use IO Ninja

Text vs Binary

Some protocols are text-based, and some are binary. Choose the representation that works best in each particular case and switch between the two kinds of data views any time you want.

Clear Timeline

Communications consist of more than just incoming and outgoing data — there are all kinds of other events (connect, disconnect, error, etc.) IO Ninja records everything in a single continuous log sheet to give you a clear timeline of events.

Log Regex Markup

Having too much information before your eyes can be counterproductive. Give yourself some visual aids by marking the log up with colors and packet delimiters — based on regular expression patterns.

Checksum Calculator

Many protocols use checksums to verify the integrity of data. IO Ninja calculates all standard checksums on the fly as you select data in the log, then conveniently displays the results in a table together with local throughputs, time differences, byte offsets, etc.

Multiple Copy Modes

Copy data from the log any way you want — as text, hex, C-array, etc. IO Ninja is smart and can guess what you want from the selection pattern so that a simple Ctrl+C always yields intuitive results.

Terminal Emulator

Sometimes, all you want is the classic terminal rendition of the incoming data. IO Ninja features a fully compatible X-Term terminal view to let you work with remote Linux boxes normally.

Transmission Facilities

IO Ninja features convenient and powerful tools for preparing packets before transmission. There's a plain text editor, a modern hex editor, and a file transmit facility — choose what works best.

Packet Templates

Even with a good hex editor, encoding fields of a binary packet by hand is hard and error-prone. With the Packet Template engine, you describe the packet structure in a C-like language, then conveniently edit your packet in the property grid.

Packet Library

Every time you transmit a packet, it goes to the Packet History pane. Re-transmit any packet with a double click, assign mnemonic names to packets, and build libraries of packets used in your line of work.

Redirect Anything

The Session Linking engine lets you redirect anything to anythingSerialTCP, UDPSSL, SSHWebSocket, etc. Start and configure two sessions, then click Link Sessions, and voila! All the data will be propagated from one session to the other.


Sometimes you need to automate your testing routine. With the Script Pane, you can generate packets programmatically, wait for and react to events, automatically respond to incoming packets, etc.

Extensible Arch

IO Ninja is highly modular, and all the plugins are open-source. See how they are implemented, modify any to your liking, or build something completely new. To make things convenient, do it with the code-assisting IDE that we use ourselves!

Interfaces, Transports, Protocols


Serial remains one of the most widely used interfaces in IoT and industrial automation. IO Ninja provides you with a rich toolset for debugging serial communications.

Serial Tap
Serial Terminal
Serial Monitor


Hardware and software Ethernet sniffers in IO Ninja shine at the live reconstruction of TCP & UDP data streams. We also provide full interoperability with the industry leader in packet capture — Wireshark.

Ethernet Tap
Ethernet Tap over SSH
Pcap Sniffer


Our hardware sniffer for I²C/SPI will give you the most convenient and easy-to-follow data view of I²C and SPI data streams. It works better than logic analyzers when you are interested in high-level data rather than low-level signal details.



TCP is rightfully called the language of the Internet. IO Ninja turns you into a professional linguist in this department.

TCP Terminal
TCP Server Terminal
TCP Flow Monitor


As a transport UDP doesn't provide the convenience and guarantees of TCP. Nevertheless, UDP has its undisputed domain of application. With IO Ninja, you have all the necessary tools to troubleshoot connectionless UDP communications.

UDP Terminal
UDP Flow Monitor
UDP Flow Analyzer


SSL is the transport of the modern Web. IO Ninja gives you powerful terminals to work on both the client and server sides of SSL connections.

SSL Terminal
SSL Server Terminal


Whenever you talk to a remote Linux box, you need SSH — so, of course, there's a convenient SSH terminal in IO Ninja.

SSH Terminal


WebSockets are widely used in Web applications nowadays. IO Ninja features both client and server-side terminals to help debug your next WebSocket application.

WebSocket Terminal
WebSocket Server Terminal


Named and anonymous pipes are important methods of inter-process communications (IPC). IO Ninja provides unique tools for pipe traffic generation and analysis. A must-have for CompuSec researchers!

File Stream Terminal
Named Pipe Server Terminal
Pipe Monitor


We proudly present the low-level USB endpoint terminals and monitors — indispensable tools when developing or analyzing USB devices. There're also specialized tools for HID (Human Interface Devices such as keyboards, mices, joysticks, etc.)

USB Endpoint Terminal
USB Monitor
HID Terminal
HID Monitor


IO Ninja is the best Modbus analyzer on the market, and we plan to expand the list of supported automation protocols gradually. Our protocol analyzers are implemented as layers so that they can be applied to raw data captured with any plugin.

Modbus Analyzer
DF1 Analyzer


IO Ninja is truly versatile, so there's much more than could be fit into the categories above.

J-Link RTT Terminal
Replay Log
TX Modifier