iTwin.js

An open source library for creating, querying, modifying, and displaying Infrastructure Digital Twins.

About this Repository

This repository is a monorepo that holds the source code to multiple iTwin.js npm packages. It is built using Rush.

See rush.json for the complete list of packages and Versioning.md for package and API versioning policies.

Each package has its own node_modules directory that contains symbolic links to common dependencies managed by Rush.

Features

• ✅ Create infrastructure digital twins of assets or projects
• ✅ Aggregate Engineering Models, Reality Data, Geographic Information Systems, Internet of Things (IoT) Data, and other standard formats
• ✅ Visualize data and engineering changes in 3D and 4D
• ✅ Analyze data to gain insights and drive new business outcomes across multiple platforms

Quick Start

• This is a sample of an iTwin viewer - a frontend application that displays infrastructure projects on browsers. It uses many of the APIs and libraries published from this repository.
• You can also look at other samples which showcases the capabilities of iTwin.js, and the iTwin Platform.

Prerequisites

• Git
• Node: an installation of the latest security patch of Node 24. The Node installation also includes the npm package manager.
• pnpm: our required package manager. It is more performant and monorepo friendly than npm. We recommend installing pnpm using corepack enable pnpm. Note you may have to use an administrator shell to run the command.
• Rush: to install npm install -g @microsoft/rush
• TypeScript: this is listed as a devDependency, so if you're building it from source, you will get it with rush install.
• Visual Studio Code: an optional dependency, but the repository structure is optimized for its use

See supported platforms for further information.

Contribution

Developer Quick Start

The following instructions will quickly set the repo up for you to edit the source code and contribute:

1. Clone the repository locally: git clone https://github.com/iTwin/itwinjs-core.git
2. Install dependencies: rush install
3. Build source: rush build
4. Run tests: rush cover

​For more information, please refer to our Contributing Guide, which provides detailed instructions on source code editing workflows, debugging tests, contribution standards, FAQs, and guidelines for posting questions.​

Interactive Testing and Feature Development

This repository includes display-test-app (DTA), a desktop-style test application built as part of the monorepo. It is the easiest way to exercise iTwin.js APIs directly against the source code in this repository. For example, it can be used to reproduce a bug, demonstrate a feature gap, or test a local change. Because it runs against the code in your working tree (not a published release), it is often a better vehicle for reproductions than online sandboxes, and as an Electron app it can also exercise desktop-only workflows such as editing.

After completing the Developer Quick Start above (which builds display-test-app along with everything else), see the display-test-app README's Getting Started and Using display-test-app sections for how to run it and open an iModel. Adding a key-in is a convenient, self-contained way to invoke whatever iTwin.js API you want to test; see Adding a key-in for a step-by-step guide with a skeletal example. If you use an AI coding agent, the repository also provides a DTA repro agent that specializes in scaffolding minimal reproductions in display-test-app.

Licensing

Copyright © Bentley Systems, Incorporated. All rights reserved. See LICENSE.md for license terms and full copyright notice.