denoland/deno

Deno is a runtime for JavaScript, TypeScript, and WebAssembly. A runtime is the program that actually executes your code, and Deno positions itself as a modern alternative for running these languages outside of a web browser. It is most commonly used to build web servers, though the README notes it can be used for many different kinds of applications. According to the project, Deno emphasizes secure defaults and developer experience. The runtime is built on V8 (a well-known JavaScript engine), Rust (a systems programming language), and Tokio (an async runtime for Rust). The README does not go deep into how those pieces fit together beyond naming them, but the practical takeaway for a non-technical reader is that Deno can run TypeScript directly without a separate compilation step, and it ships with built-in tools and a standard library so you do not need to assemble a stack from many small pieces. A typical first program is a tiny web server: you write a short snippet calling Deno's serve function in a TypeScript file, then run it from the command line with a flag that explicitly grants network access. That permission flag illustrates the secure-defaults idea, the runtime restricts what scripts can do unless you opt in. You would reach for Deno when you want to write JavaScript or TypeScript code that runs on a server or your own machine and you prefer a single integrated tool over assembling a runtime, type-checker, and package tooling separately. The project also points to companion offerings (Deno Deploy hosting, the JSR package registry, an official standard library) for users who want to go further. The repository itself is written primarily in Rust.