- Category
- Developer Tools
- Rank
- No. 452Tools index
Previous survey · No. 457 ·
- Pricing
- Open Source
- Type
- TOOL
- Builder
- microsoft
- GitHub
- 9.7k stars
- Latest release
- @microsoft/fast-test-harness_v0.5.0
- Date
About
Microsoft's adaptive interface system — design tokens, components, and tooling for building modern web experiences with web components.
What it does
FAST supplies the foundations for teams to create reusable, standards-based custom elements. Its core library handles reactive state, data binding, templates, styles, DOM policy, observation, and component registration. Components can run with major frontend frameworks or directly in the browser.
Why it's ranked here
FAST is compelling when interoperability matters more than adopting one framework’s component model. It combines a broad browser runtime with declarative templates, routing, testing support, and server rendering. The cost is scope: this repository is infrastructure for component authors, while its recommended ready-made Fluent components live elsewhere.
What's good
The core library exposes focused building blocks for one-way and two-way binding, signals, observable state, repeated templates, conditional rendering, styles, and DOM safeguards. Distribution includes regular, minified, and debug ES modules. Browser tests explicitly cover Chrome, Firefox, and Safari engines, while the test harness supports client and server rendered fixtures.
Tradeoffs
FAST presents a large surface rather than a small custom-element wrapper. Teams must choose among runtime primitives, declarative templates, routing, conversion, server rendering, and testing utilities. Its ready-made Fluent component set is maintained in another repository. The build also assumes current Node and npm generations, which may conflict with older development environments.
How to use it well
Choose FAST when a design-system team needs reusable custom elements that can cross framework boundaries or support gradual adoption. Start with the core element library, add declarative or server-rendering facilities only when required, and test across the supplied browser targets. Look to Fluent UI for finished controls. FAST itself does not replace product design or provide that component catalogue here.
Technical notes+
The root package.json defines a private npm workspace monorepo spanning build, packages, sites, and CSR and SSR examples, with Node >=22.18.0 and npm >=10.0.0. packages/fast-element/src/index.ts exports binding, observation, templating, styling, schema, component, and DOM-policy APIs. packages/fast-element/rollup.config.js emits standard, minified, and debug ESM bundles. packages/fast-test-harness/server.mjs combines a Node HTTP server with Vite middleware, caches generated SSR fixtures, validates fixture identifiers, and blocks static-file path traversal. crates/microsoft-fast-build/src/lib.rs implements Rust template rendering with optional state, locators, hydration markers, chunked output, and WASM bindings. crates/microsoft-fast-convert/src/lib.rs converts declarative templates to WebUI prerelease HTML or FAST v3 TypeScript source.
Observed
- License
- MIT
- Primary languages
- TypeScript and Rust
- Packaging
- Private npm workspace monorepo with published package surfaces and paired Rust crates
- Core interface
- Library APIs for standards-based Web Components
- Module output
- ES modules, including minified and debug builds
- Browser support
- Playwright projects target Chromium, Firefox, and WebKit
- Server rendering
- Rust renderer supports full HTML output, chunked output, custom-element lookup, and WASM bindings
- Development requirements
- Node 22.18 or newer and npm 10 or newer
Read from README.md, package.json, packages/fast-test-harness/server.mjs, packages/fast-element/rollup.config.js, packages/fast-element/playwright.config.ts, packages/fast-element/playwright.declarative.config.ts, packages/fast-element/playwright.declarative.webui.config.ts, packages/fast-router/src/index.ts, packages/fast-element/src/index.ts, packages/fast-test-harness/src/index.ts, packages/fast-element/src/declarative/index.ts, lage.config.js, beachball.config.js, crates/microsoft-fast-build/src/lib.rs, crates/microsoft-fast-convert/src/lib.rs.
What it can do
Generate design tokens
Design specifications and brand guidelines → Standardized design token files
Create web components
Component specifications and design requirements → Reusable web component code
Build adaptive user interfaces
Design system configuration and component library → Responsive web interface components
Generate component documentation
Web component definitions and usage patterns → Developer documentation and usage guides
Customize design system themes
Brand colors, typography, and styling preferences → Theme configuration files and CSS variables
Export component library
FAST design system configuration → Packaged component library for web applications
Intel on FAST
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