--- title: "How Definitely Typed Changed TypeScript Forever" description: "Discover the story behind Definitely Typed with its creator, Boris Yankov, and learn how it became essential for type-safe JavaScript in the TypeScript ecosystem." url: https://www.callstack.com/podcasts/how-definitely-typed-changed-typescript-forever updated: 2026-10-24T08:39:42.495Z --- # How Definitely Typed Changed TypeScript Forever Discover the story behind Definitely Typed with its creator, Boris Yankov, and learn how it became essential for type-safe JavaScript in the TypeScript ecosystem. _Guest: Boris Yankov, Software Engineer @ Callstack · Host: Mike Grabowski, CEO & Founder @ Callstack · Published 2025-03-26 · Duration 39:00 · Category: Open Source_ Listen: [YouTube](https://youtu.be/HyimNixYw54) · [Spotify](https://open.spotify.com/episode/6970G60iS4uQuOO0FwTuIh?si=BCagwkksRgWnbRHXxup8IA) · [Apple Podcasts](https://podcasts.apple.com/us/podcast/how-definitely-typed-changed-typescript-forever-react/id1525543072?i=1000700911262) · [SoundCloud](https://soundcloud.com/user-985069846/how-definitely-typed-changed-typescript-forever-react-universe-on-air-26) Ever wondered why TypeScript feels so seamless with your favorite JavaScript libraries? It’s not just luck—it’s Definitely Typed, a project that plays a crucial role in enabling TypeScript developers to use JavaScript libraries with type safety and autocompletion. In this Coffee Talk episode of React Universe On Air, Mike has invited Boris Yankov, the repository’s creator and long-time maintainer, to share the story of Definitely Typed. They discuss how this open-source repository became the backbone of type safety in TypeScript. ## The full story of Definitely Typed Here’s what you can expect from this episode: - **The early days of TypeScript**—Boris takes us back to 2012, just after TypeScript's release. He discusses the challenges of building the first type definitions and how early contributions helped lay the foundation for the TypeScript ecosystem we know today. - **From passion project to Open Source giant**—What began as a personal project quickly grew into a community-driven repository with thousands of contributors. Boris explains how automation and Microsoft’s support helped scale Definitely Typed from a niche tool to an open-source giant. - **TypeScript vs. Flow** Mike and Boris discuss why TypeScript's pragmatic approach to type safety and strong backing from Microsoft led to its success over Flow. They talk about how Definitely Typed contributed to TypeScript's widespread adoption by offering robust type definitions for JavaScript libraries, establishing its place as the go-to choice for typed JavaScript. - **How Definitely Typed works**—Boris provides a technical overview of how Definitely Typed integrates with NPM and TypeScript’s tooling, making type definitions accessible through the @types packages. He explains the automated publishing process and how contributors' updates are published to NPM, ensuring developers rarely encounter issues with type definitions in their projects. - **The open-source dynamics**—Boris shares the human side of open source, discussing the project's organic collaboration model and why it doesn’t need a strict leadership structure. He also explains how new contributors can get started.**‍** - **Favorite TypeScript features**—To wrap up, Boris and Mike share their favorite TypeScript features, such as Discriminated Unions, and offer development tips for working with type definitions. ## Learn more about Definitely Typed - Mike Grabowski on [X](https://x.com/grabbou), [BlueSky](https://bsky.app/profile/grabbou.com), and [GitHub](https://github.com/grabbou) - Boris Yankov on [X](https://x.com/borisyankov), [BlueSky](https://bsky.app/profile/borisyankov.com), and [GitHub](https://github.com/borisyankov) - [Definitely Typed homepage](https://definitelytyped.org/) - [Definitely Typed repo](https://github.com/DefinitelyTyped/DefinitelyTyped) Insights ## Learn more about Open Source Here's everything we published recently on this topic. [View all](https://www.callstack.com/insights) - [Visualizing Open Source Licenses to Analyze Compliance and Reduce Legal Risk](https://www.callstack.com/blog/visualizing-open-source-licenses-to-analyze-compliance-and-reduce-legal-risk) (Aug 7 · Article): Discover how license-kit visualize maps and analyzes your dependency graph, helping you spot license issues, duplicates, and restrictive packages with interactive views, stats, and AI-powered summaries. - [Introducing the OMH Cloud Storage Module](https://www.callstack.com/blog/introducing-the-omh-cloud-storage-module) (Oct 14 · Article): Discover the OMH Cloud Storage Module. This open-source solution simplifies cloud storage integration for React Native apps. - [Introduction to the React Native OMH Maps Library](https://www.callstack.com/blog/introduction-to-the-react-native-omh-maps-library) (Jul 12 · Article): Discover how the React Native OMH Maps library simplifies map integration with cross-platform compatibility, ease of use, and customization options. - [Behind the Scenes of React Native 0.74 Release](https://www.callstack.com/podcasts/behind-the-scenes-of-react-native-0-74-release) (Apr 22 · Podcast): Join the release crew members to find out what new features and improvements React Native 0.74 brings to the cross-platform development world. - [Callstack OSS Update](https://www.callstack.com/podcasts/callstack-oss-update) (Apr 27 · Podcast): April 2023 Callstack OSS Update: RFC for Expo Config Plugins, Re.Pack & Paper news. - [NPM Kiosk and Open Source Monetization](https://www.callstack.com/podcasts/npm-kiosk-and-open-source-monetization) (Feb 21 · Podcast): Explore the pros, cons, and lessons from gating access to open source libraries, plus insights on handling payments with tools like NPM Kiosk and Reassure. - [React Native Paper 5.0 - What’s New?](https://www.callstack.com/blog/react-native-paper-5-0) (Dec 6 · Article): React Native Paper 5.0 is here! Dive into the latest updates and improvements. - [React Native Programming Languages](https://www.callstack.com/podcasts/coffee-talk-5-react-native-programming-languages) (Sep 15 · Podcast): Join Łukasz Chludziński and Abi Thiao as they discuss React Native programming languages ranging from JavaScript and TypeScript to Lua. - [Reassure - Open Source Tool Measuring Performance Regression](https://www.callstack.com/podcasts/reassure-performance-regression-measurement-tool) (Jul 28 · Podcast): Explore Reassure, an Open Source tool for measuring performance regression in React Native apps.