Serial Terminal

A free, open-source serial port (COM) terminal for Windows. It is built for everyday work with microcontrollers such as STM32, Arduino and ESP32.

It was written because the existing tools were either paid, hard to read, or limited, for example by a fixed line length or by not being able to log to a file and watch the output at the same time.

Website: https://kod47.github.io/serial-terminal/

Features

Display

• No line-length limit. Word wrap is optional, with horizontal scrolling when it is off.
• Large, readable monospace font. Zoom with Ctrl + mouse wheel or Ctrl +/−.
• Dark and light themes.
• Separate colors for received data (RX), sent data (TX), info messages and errors.
• Optional timestamps with millisecond precision.
• Four display modes: Text, HEX, HEX + ASCII and Modbus RTU. The HEX modes start a new line after an idle gap, so each packet shows up on its own line.
• Control characters stay visible (␀ ␛ …) instead of disappearing.
• A buffer of 100,000 lines. Auto-scroll pauses when you scroll up and resumes when you scroll back to the bottom.
• Select lines and press Ctrl + C to copy them.

Keyword highlighting and filter

• Lines that contain a keyword are colored, for example error in red and warn in orange. See below.
• Filter (Ctrl+F) shows only the lines that contain a given text.

Several ports at once

• Each port opens in its own tab (Ctrl+T). Every tab has its own settings, output, log and graph.
• A colored dot on each tab shows whether it is connected, waiting to reconnect or disconnected.

Logging

• Start log (Ctrl+L) writes to a file while you keep monitoring.
• File names are generated automatically, for example COM5_2026-09-24_14-30-00.log. You choose the folder.
• Save as... (Ctrl+S) saves everything currently on screen.

Connection

• Port list with device names, for example "STMicroelectronics Virtual COM Port". It updates automatically when USB devices are plugged in or removed.
• Any baud rate, including custom values. Data bits, parity, stop bits and flow control are configurable.
• Manual DTR and RTS control.
• Auto-reconnect after the board is reset or the cable is unplugged.

Sending

• Two independent send lines, each with its own text or HEX mode and line ending (None, CR, LF or CRLF).
• Repeat sends a line periodically, every 10 ms or more. Useful for polling.
• The text stays in the box after sending. Enter sends, Up/Down browses the history.
• 8 macro buttons: left-click sends, right-click edits.
• HEX input accepts 01 03 00 0A, 01030A or 0x01,0x03.
• Send file with adjustable chunk size, a delay between chunks and a progress bar.

Modbus RTU

• Each frame is decoded: slave, function, addresses and values, exceptions, and a CRC check.

  01 03 00 00 00 0A C5 CD  [Slave 1 · Read Holding Registers · start 0, count 10 · CRC OK]
  

• +CRC appends the CRC16 to HEX data automatically. Type 01 03 00 00 00 0A and the CRC is added when the frame is sent.

Live graph

• Numbers in received lines are plotted in real time. temp=23.5 hum=40 gives named series, and 12 34 56 gives series #1, #2, #3.
• The time window can be 10 s to 5 min. The Y axis scales automatically (optionally always including 0) or uses a manual Min/Max.

Interface

• Full menu (File, Edit, Connection, View, Tools, Help) with keyboard shortcuts.
• Each toolbar can be shown or hidden from View → Toolbars.

All settings are saved automatically to %AppData%\SerialTerminal\settings.json.

Highlight rules

Few serial terminals can do this. You set keywords and colors once, and every received or sent line that contains a keyword stands out immediately. You no longer need to search through thousands of lines for an error.

• Open it from Tools → Highlight rules... or with the Highlight... button.
• Each rule has an on/off switch, the text to look for, an optional Match case setting and a color.
• The first matching rule sets the line's color. The rules apply to all tabs, including lines that are already on screen.
• Combine it with the Filter to show only the lines you care about.

Download

⬇ Download SerialTerminal.exe (v0.2.0, Windows 10/11 x64, ~62 MB)

No installation needed: download the file and run it. It does not require .NET.

Windows SmartScreen may warn about an unknown publisher. Click More info → Run anyway.

Release notes and older versions are on the Releases page.

Build from source

Requires the .NET 10 SDK.

git clone https://github.com/kod47/serial-terminal.git
cd serial-terminal
dotnet run

Standalone .exe

This creates a single SerialTerminal.exe that runs without installing .NET:

dotnet publish -c Release -r win-x64 --self-contained true -p:PublishSingleFile=true -p:IncludeNativeLibrariesForSelfExtract=true

The output is in bin\Release\net10.0-windows\win-x64\publish\.

Project structure

Path	Purpose
Core/SerialConnection.cs	Opening the port and the background read loop
Core/LineAssembler.cs	Turns raw bytes into display lines (Text/HEX/Modbus)
Core/ModbusRtu.cs	Modbus RTU CRC and frame decoder
Core/HighlightRule.cs	Keyword highlighting
Core/GraphData.cs	Extracts numeric values for the graph
Core/PortEnumerator.cs	Port list with device descriptions (WMI)
Core/LogWriter.cs	Logging to file
Core/AppSettings.cs	Settings persisted to JSON
MainViewModel.cs	Tabs, shared port list, global options
SessionViewModel.cs	One tab: port, output, sending, log, graph
ChartControl.cs	Live chart
MainWindow.xaml, SessionView.xaml	User interface (WPF, Fluent theme)

Contributing

Bug reports, ideas and pull requests are welcome.

Support the project

This program is free. If it saves you time and you would like to support further development, you can make a donation via PayPal to:

kod447@gmail.com

Thank you!

License

MIT: free to use, modify and distribute, including commercially.