Universal Robots URCap is the official extension model for all UR cobots — UR3, UR5, UR10, UR16 (CB-Series since 2008, e-Series since 2018) plus UR20/UR30 (2023, Series e). A URCap is a `.urcap` file (effectively a JAR + bundled HTML/JS), installed on the PolyScope teach pendant (Linux on ARM); it extends the UI with new Program Nodes (tiles in the program tree, e.g. 'Pick & Place from Conveyor'), Installation Nodes (hardware configuration), Toolbars, and Daemons (background services).
Tech stack: **PolyScope 5.x** (CB/e-Series) is based on OpenJDK 8 + Eclipse RCP — URCaps are written in Java 8 (Swing for UI). **PolyScope X** (2024+, the new generation on UR20/UR30) is built on Linux + web tech — URCaps are HTML/CSS/TypeScript Single Page Apps. Both targets can be addressed from a single URCap via the `cross-platform` SDK. Regardless of the UI, a URCap injects **URScript** (the robot's procedural language, syntax similar to Python) into the generated PolyScope program.
Wire protocols for communicating with external systems:
**RTDE (Real-Time Data Exchange)** — TCP port 30004, 125 Hz update rate (every 8 ms), allows telemetry to be received (joint positions, TCP pose, forces) and setpoints to be sent. **Dashboard Server** (port 29999) — load, play, stop, status commands — used for orchestration. **Primary Interface** (30001) and **Secondary Interface** (30002) — legacy URScript streaming. **XML-RPC** (port 30003, e-Series only) — an alternative to RTDE.
ROS support: the official `Universal_Robots_ROS2_Driver` (since 2022, maintained by UR + PickNik Robotics) uses RTDE under the hood and exposes `joint_trajectory_controller` plus `cartesian_compliance_controller`. The earlier `ur_modern_driver` for ROS 1 was community-maintained.
An SDK (Software Development Kit) is a curated set of libraries, interfaces, tools, sample code, and documentation intended for building applications and integrating with a specific hardware device, platform, or service. In robotics, an SDK typically exposes device control, telemetry, sensor access, configuration, and execution functions, significantly reducing the time-to-first-integration for developers targeting a specific robot or platform.
An API Library is a software package that exposes programmatic interfaces for communicating with a device, service, or system. In robotics it typically forms a lightweight integration layer built on top of the manufacturer's official API or an open-source project, abstracting low-level protocol details and providing language-native bindings (Python, C++, Java, etc.).
A Developer Tool is software designed to support the development workflow, including configuration, debugging, testing, monitoring, validation, and integration of robotic and embedded systems. Examples include IDE plugins, visual debuggers, log analysers, hardware-in-the-loop (HIL) test harnesses, and code-generation utilities specific to robotics platforms.
A family of official SDKs and APIs provided by robot manufacturers: Boston Dynamics (Spot SDK), ABB (RobotStudio), KUKA (RSI / KUKA Sunrise), Universal Robots (URCap / RTDE), Agility Robotics (Digit SDK), Apptronik (Apollo SDK).
Over 75,000 UR cobots sold by 2024; the UR Marketplace has ~300 public URCaps and ~150 certified partners. Deployments: BMW (door assembly with UR10), Volkswagen (headlight bonding with UR5), Mercedes-Benz (UR5e with Robotiq gripper in quality testing), Continental (packing with UR10e), Nissan (transmission assembly with UR10), Foxconn (electronics testing with UR3), Ford (pre-assembly with UR10). Collaborative applications in e-commerce (Amazon, DHL) and medical device assembly (Boston Scientific).
The UR+ ecosystem (ur-plus.com) with ~300 URCaps and ~750 certified HW components (grippers, sensors). github.com/UniversalRobots/Universal_Robots_ROS2_Driver ~890★. The forum.universal-robots.com has ~30k registered developers. UR Academy with free online courses (~200k graduates).
OpenJDK 8 for PolyScope 5.x URCaps. Node.js + TypeScript for PolyScope X URCaps. URSim (the official simulator VM) is free. The URCap SDK is free, but URCap digital signing via the UR Marketplace requires partner registration (free of charge).
License family: Proprietary – Commercial
Full cross-platform URCap support (one codebase for 5.x + X), AI Accelerator integration (NVIDIA Jetson on the UR pendant).
A new PolyScope generation (web-based UI), URCaps as HTML/TS SPAs, launch of UR20/UR30.
Official ROS 2 driver co-developed with PickNik Robotics — ros2_control + RTDE.
New e-Series controller, built-in force/torque sensor, URCap SDK with the new Cartesian API.
Real-Time Data Exchange (port 30004) as the official wire protocol for external control.
Introduction of URCap — the Java plug-in model in PolyScope 3 on CB3.
First release alongside the UR5 robot. No URCap yet — only URScript over TCP.