Jint

Jint is a modern ECMAScript interpreter for .NET. It runs JavaScript directly in your process without native dependencies, bytecode generation, or a separate runtime.

Jint targets .NET Framework 4.7.2, .NET Standard 2.0/2.1, .NET 8, and .NET 10. Start with the documentation or install the core package:

dotnet add package Jint

Quick start

The examples below assume using Jint;.

Evaluate JavaScript

var engine = new Engine();
var result = engine.Evaluate("40 + 2").AsNumber();

Expose .NET and call JavaScript

var engine = new Engine()
    .SetValue("log", new Action<string>(Console.WriteLine))
    .Execute("""
        function greet(name) {
            const message = `Hello, ${name}!`;
            log(message);
            return message;
        }
        """);

var greeting = engine.Invoke("greet", "Ada").AsString();

Prepare code that runs repeatedly

var script = Engine.PrepareScript(
    "items.reduce((sum, value) => sum + value, 0)",
    source: "sum.js",
    strict: true);

var engine = new Engine();
engine.SetValue("items", new[] { 1, 2, 3 });

var total = engine.Evaluate(in script).AsNumber();

Prepared<Script> and Prepared<Module> are thread-safe and may be shared across engines. JavaScript objects are not: a JsValue that contains an object belongs to the engine and realm that created it.

Features

• Modern ECMAScript, modules, promises, async functions, generators, Intl, and Temporal
• Direct projection of .NET values, delegates, objects, collections, and types
• Synchronous and asynchronous module loaders
• Execution constraints, hardened untrusted-code defaults, and security diagnostics
• Profiling, statement coverage, debugging, and Chrome DevTools Protocol integration
• Opt-in Web APIs and Node-compatible modules
• A headless browser, command-line tool, and MCP server

Browser and Node APIs are not installed by default. Hosts explicitly grant the capabilities each script needs.

Used by

Projects using Jint include RavenDB, EventStoreDB, Orchard Core, Elsa Workflows, Docfx, and JavaScript Engine Switcher.

Additional packages

Jint is the core package used throughout this README. Add another package only when the application needs an optional debugging or browser surface.

Package	Purpose
Jint.DevTools	Chrome DevTools Protocol server for debugging and profiling an engine
Jint.Browser	Headless HTML, DOM, navigation, networking, storage, and content extraction
Jint.Browser.Tool	jint-browser command-line tool
Jint.Browser.Mcp	Model Context Protocol server for browser automation

See Additional packages for dependencies, target frameworks, and common combinations.

Branches and releases

Jint 5 is under development on main and has not been released. This branch includes breaking changes; development packages are available from the preview feed.

The 4.x branch is the maintenance lane for Jint 4.16. Changes there preserve compatibility and focus on non-breaking correctness and conformance fixes. The 3.x branch receives only security and severe-correctness maintenance.

Pull requests target main unless they are explicit backports. See Branches and Releases for the complete policy and Migrating to Jint 5 when upgrading from Jint 4.

Standards conformance

These percentages describe the pinned test corpora in this repository, not the entire web platform.

Surface	Result	Measured scope
ECMAScript and ECMA-402	99.9% (102,585 / 102,692)	Generated test262 cases from annexB, built-ins, intl402, language, and staging; 107 cases are skipped
WinterTC Minimum Common API	79.5% (62 / 78)	59 members present and 3 correctly absent for Jint's global shape; the remaining 16 are WebAssembly, which Jint declines by design
Jint runtime Web APIs	92.9% (38,649 / 41,581)	Assertions in the vendored .any.js WPT corpus across 44 suite directories
Jint.Browser	84.0% (9,691 / 11,541)	Tests in the gated in-process browser WPT corpus

The test262 result uses commit 419d3e0. Read the detailed scope and exclusions for ECMAScript, Web APIs, and Jint.Browser.

This is the beginning of the README. Read the rest at the original. Read the full README ↗