opcua-client-gui (FreeOpcUa)

What you actually use it for

• Giving Python developers a GUI that shares a stack with their code, so what the GUI can do asyncua can do too.
• Cross-platform browsing where a pip install is easier to get approved than a vendor installer.
• Subscribing to a handful of nodes and watching updates while you develop the equivalent asyncua subscription.
• Checking whether a decoding problem is in your code or in the stack, by opening the same node in the GUI that your script is failing on.
• Quick event subscriptions against a server whose Part 9 behaviour you are still mapping.

Walkthrough

1. Install from PyPI into a virtual environmentThe distribution name is opcua-client, not opcua-client-gui. Install it into its own virtual environment so its Qt and asyncua pins do not collide with your project's, and check the Python version the current release requires before you start.
2. Launch and enter an endpoint URLPaste a full endpoint, for example opc.tcp://opcuademo.sterfive.com:26543, and connect anonymously with no security first. The client stores recent endpoints, which is convenient and also means a stale entry can send you to the wrong machine.
3. Configure security if you need itSet the security policy, message security mode and the paths to your client certificate and private key. Because this is asyncua underneath, the certificate and key files are ordinary PEM or DER files you can also point your scripts at.
4. Browse the tree and read the attribute and reference panesSelecting a node populates its attributes and references. Use the HasTypeDefinition reference to identify the ObjectType, then browse that type to learn what an instance is supposed to contain.
5. Add nodes to the subscription paneDropped nodes become monitored items with a live value, StatusCode and timestamp. Compare what you see here against what your asyncua subscription receives; a difference usually means your handler, not the server.
6. Reuse what you learned in asyncua directlyThe GUI is a prototyping surface. Once the node paths and subscription parameters are settled, move them into asyncua code or into the uals, uaread and uasubscribe CLI tools for anything repeatable.

What it will not do

• Community-maintained with a small contributor base; release cadence and platform packaging are less predictable than a vendor tool.
• Qt dependency, which is the most common cause of a failed install on a minimal Linux image.
• Thin on historical access, alarms depth, aggregates and performance testing compared with UaExpert.
• No PubSub support.
• Complex structure decoding depends on what asyncua supports for the server's chosen mechanism, so a server exposing only a legacy type dictionary may leave values undecoded.

Alternatives

Last verified 7 September 2026 against OPC UA 1.05.07. OPC UA Connect is an educational resource and is not affiliated with the OPC Foundation.