XState — State Machines & Statecharts for Complex Logic

What XState Does

• Finite state machines — explicit states and transitions
• Statecharts — hierarchical, parallel, history states
• Actors — async, message-passing concurrency model
• Visualizer — Stately Studio for drag-and-drop editing
• Guards & actions — conditional transitions and side-effects
• Delayed transitions — timeouts without setTimeout juggling
• Model-based testing — auto-generate tests from machines

Architecture

A machine is a pure object describing states, events, transitions, and effects. createActor(machine) spawns a running instance. Actors can spawn child actors, creating a hierarchy. Works in any JS runtime; bindings exist for React, Vue, Svelte, Solid.

Self-Hosting

Client-side library. Stately Studio is a SaaS for visual editing (optional), but machines run anywhere.

Key Features

• Statecharts with hierarchy & parallel states
• Actor model for concurrency
• Fully type-safe (v5 uses setup() for inference)
• Visual editor (Stately Studio)
• Test generator (@xstate/test)
• Framework-agnostic core
• Bindings for React, Vue, Svelte, Solid
• SCXML export

Comparison

FAQ

Q: When should I use XState? A: Complex UI flows (multi-step forms, payment flows, video players, collaborative editing). For simple global state, Zustand is enough.

Q: What is the Actor model? A: A concurrency model where each actor is an independent state machine that communicates via messages, avoiding race conditions from shared state.

Q: What changed in v5? A: v5 introduces a setup() API for better TS type inference, simplifies the actor system, and replaces interpret with createActor.

Sources & Credits

• Docs: https://stately.ai/docs
• GitHub: https://github.com/statelyai/xstate
• License: MIT