lit

Lit provides a clean, decorator-based API for building web components with reactive properties and efficient DOM updates. The library handles XSS concerns well through its template system - the `html` tagged template automatically escapes values in text positions, though you need to be careful with attribute bindings and explicitly use unsafe directives when needed. Error messages clearly indicate when you're doing something potentially dangerous.

From a security standpoint, Lit follows secure-by-default principles. Input validation is your responsibility (as it should be), but the template system doesn't surprise you with unexpected HTML injection. The dependency tree is remarkably light - mainly @lit/reactive-element and lit-html with minimal transitive dependencies, reducing supply chain risk. Google maintains it actively with consistent CVE response when issues arise.

The main gotcha is understanding the difference between properties and attributes for data binding. The documentation clearly explains this, but it trips up newcomers. TypeScript support is excellent, which helps catch binding errors at compile time rather than runtime.

Lit makes building web components genuinely enjoyable. The decorator-based API (@customElement, @property, @state) feels natural and the reactive property system just works. TypeScript integration is first-class—decorators provide full type inference, and the html template tag gives you proper autocomplete for element attributes and event handlers in VSCode. Error messages are clear and actionable, like when you forget to mark a reactive property or misuse a directive.

The documentation is outstanding. The tutorial walks you through real patterns, the playground lets you experiment immediately, and the API docs include practical examples for every decorator and directive. Migration guides between major versions are detailed with codemods provided. Day-to-day, the small bundle size (5kb core) and excellent performance make it a no-brainer for component libraries.

One gotcha: the reactive update lifecycle takes some learning—understanding when to use @property vs @state and when requestUpdate() is needed. The docs cover this well, but it's not instantly obvious from the API surface.

Lit has been a pleasure to work with after coming from both vanilla web components and heavier frameworks. The learning curve is remarkably gentle - if you know HTML, CSS, and basic JavaScript, you're 80% there. The template literal syntax feels natural and the reactive properties 'just work' without weird gotchas. The official playground and tutorial walk you through real components step-by-step, which got me productive in an afternoon.

Error messages are genuinely helpful. When I forgot to add @property decorators or made lifecycle mistakes, Lit pointed me to the exact issue with clear explanations. The dev mode warnings catch common mistakes before they become bugs. Debugging is straightforward since it's just JavaScript - no virtual DOM abstractions to reason through, and browser devtools work perfectly.

Community support is solid. GitHub issues get responses quickly, and the documentation covers most scenarios I've encountered. The Lit site has a patterns section that addresses real-world needs like forms, dynamic imports, and SSR. When I needed to integrate with existing frameworks or share state, the interop story was clear and well-documented.