Unlocking Industrial Data: A Complete Guide to the WinCC REST API

Unlocking Industrial Data: A Complete Guide to WinCC REST API

What Exactly Is the WinCC REST API?

The WinCC REST API is an OPC UA–based RESTful interface that allows external clients to interact with a running WinCC project using standard HTTP methods (GET, POST, PUT, DELETE). It exposes:

• Process tags (variables) – read/write current values
• Alarms & messages – fetch active or archived alarms
• Archived data – historical tag values over time ranges
• System information – connection status, license info

Unlike older DCOM or OPC DA interfaces, REST uses JSON over HTTP/HTTPS—meaning any programming language (Python, JavaScript, C#, etc.) or tool (Postman, Node-RED, Power BI) can integrate without special COM libraries or Windows-only dependencies.

Note: The REST API does not replace WinCC’s internal OPC UA server. It acts as a higher-level, developer-friendly wrapper, often simplifying authentication and data formatting.

Request / response patterns

• Methods: GET for read, POST for queries or writes (many implementations use POST for complex queries), PUT/PATCH for updates, DELETE for removal where supported.
• Payload formats: JSON is primary. Responses include value, quality/timestamp metadata, status codes.
• Timestamps often use ISO 8601 with timezone info; some systems use epoch ms.

Example (pseudo-HTTP) — read a single tag value: Request: GET /api/tags/Plant/Unit1/TankLevel Authorization: Bearer Response (JSON): "tag": "Plant/Unit1/TankLevel", "value": 72.4, "quality": "GOOD", "timestamp": "2026-04-10T09:23:12.123Z"

Example — write a tag value (pseudo): PUT /api/tags/Plant/Unit1/PumpStart Authorization: Basic Content-Type: application/json Body: "value": true

Response: 200 OK or 204 No Content

Example — query historical values (pseudo): POST /api/history/query Body: "tags": ["Plant/Unit1/TankLevel"], "from": "2026-04-09T00:00:00Z", "to": "2026-04-10T00:00:00Z", "aggregation": "raw"

2. Scope and Versions

It is vital to distinguish between the two major Siemens WinCC architectures, as their REST API implementations differ significantly:

Part 5: Core API Endpoints and Examples

Let’s assume your WinCC server is at http://192.168.1.100. Here are the critical REST endpoints.