WebContainer API
Browser-based Node.js runtime that apps embed to execute, interpret and refactor AI-generated code inside the user's browser tab, marketed as a runtime for AI agents; the engine under Bolt.new.
Find alternatives to WebContainer API
What it does
- Agentic coding
- Code generation
Features 4
- Native Package ManagersRuns native npm, pnpm and yarn in the browser, up to 10x faster than local.
- Full Browser SupportRuns in all major browsers, from Chromium-based to Firefox and Safari TP.
- Major Framework SupportSpins up disposable environments running any major modern framework.
- WebAssembly SupportRuns ported languages and frameworks compiled to Wasm inside WebContainers.
Sources
- Pricing
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Personal $0, "Non-commercial usage with attribution", "Up to 25,000 API sessions per month" (standard s4.1 row 1); Enterprise "Contact sales".
- Description
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Official documentation · 10 Oct 2026
"In-Browser Code Execution for AI"; "Execute, interpret, and refactor AI-generated code directly in the browser"; "The best runtime for your AI Agents".
- Sold within
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Official documentation · 10 Oct 2026
Licensed directly: "Licensing is required for production usage of the API in a commercial, for-profit setting", with an API key per account.
- Name
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Pricing section titled WebContainer API.
- URL
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Official documentation · 10 Oct 2026
Own domain, "Dev environments. In your web app."; AI page https://webcontainers.io/ai.
- Deployment
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Official documentation · 10 Oct 2026
Code runs inside the end user's browser tab, not on a StackBlitz server.
- Interfaces
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Official documentation · 10 Oct 2026
npm package @webcontainer/api used with API keys.
Also from StackBlitz
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Bolt.new Platform
Bolt.new builds web and mobile apps from a chat prompt in the browser: a coding agent writes and runs the code, and Bolt Cloud supplies the database, domains and hosting.
Open StackBlitz in the directory
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