# Best Free OPC and Industrial Connectivity Software in 2026

Source: https://listme.name/best/opc-and-industrial-connectivity-software/free

OPC and connectivity software sits between PLCs and devices on one side and SCADA, historians and cloud systems on the other. This ranking weighs driver coverage and OPC UA support first, then operating system reach, licensing and trial terms, and local support.

## 1. open62541 (score 77.5)

Free MPL-2.0 OPC UA library in C99 that runs on Windows, Linux, RTOS and Android. It suits developers who write their own servers and clients, and it is not a configurable gateway or a client tool.

- Best for: Developers building OPC UA servers and clients in C
- Free and open source | Windows, Linux, Android | open source (MPL-2.0)
- Website: https://open62541.org/
- Page: https://listme.name/software/open62541

## 2. Telegraf (score 72.0)

Open-source MIT agent with OPC UA and Modbus input plugins, built for Windows, macOS and Linux. It collects metrics into time-series and messaging outputs rather than acting as an OPC server or gateway.

- Best for: Open-source OPC UA and Modbus data collection
- Free and open source | Windows, macOS, Linux | open source (MIT)
- Website: https://www.influxdata.com/time-series-platform/telegraf/
- Page: https://listme.name/software/telegraf

## 3. UaExpert (score 70.0)

A free OPC UA reference client for browsing, reading, writing and subscribing, on Windows and Linux. It is a testing tool rather than connectivity software, and plugins need keys above set limits.

- Best for: Testing and commissioning OPC UA servers
- Free | Windows, Linux
- Website: https://www.unified-automation.com/products/development-tools/uaexpert.html
- Page: https://listme.name/software/uaexpert