Browser-based code environments let developers run examples without first installing a local toolchain. Embedded examples can therefore reduce time to first hello world (TTFHW).
StackBlitz
- Founded. 2017.
- Strengths. WebContainers technology runs entire Node.js / npm environments in the browser via WebAssembly; near-instant boot.
- Bolt. StackBlitz’s AI app-building product, launched in 2024, transforms text prompts into working web apps.
- Used by. Angular team (official Angular docs sandboxes), many Vue/React/Svelte docs sites, MDN.
CodeSandbox
- Founded. 2017 by Ives van Hoorne.
- Acquired. By Together (formerly CodeSandbox, then merged with Together AI in 2024).
- Strengths. Cloud development environments running real VMs; supports any language; collaborative coding.
- API. APIs for spinning up isolated environments programmatically: used by some DevRel teams for “click to try” experiences.
Replit
- Founded. 2016 by Amjad Masad.
- Positioning. “App and site builder in your browser” with deep AI integration (Replit AI Agent, Replit Bounties).
- Strengths. Hundreds of integrations; mobile and web project sharing; very accessible for beginners.
- Used by. Education-heavy contexts; bootcamps; individual builders.
CodePen
- Founded. 2012 by Chris Coyier, Tim Sabat, Alex Vazquez.
- Strengths. Front-end only (HTML/CSS/JS); social discovery; active front-end community.
- Used by. Front-end tutorials, CSS demos, generative-art experiments.
Glitch
- Founded. 2017 (by Fog Creek / Anil Dash team).
- Acquired. Multiple ownership changes; reduced investment.
- Strengths. Remixing model; instant Node.js apps with public URLs; favoured by web educators and prototypers.
- Status. Less active than during 2017 to 2020 peak.
JSFiddle, JSBin
- Older browser-based front-end playgrounds. Still occasionally used; largely superseded by CodePen for new content.
Specialised sandboxes
- WebContainers. StackBlitz’s underlying technology, also licensable for embedding.
- Sandpack. CodeSandbox’s open-source embedding library; widely used in technical blogs and docs.
- MDX-embedded code samples. Many docs sites embed live code samples directly via React-based components.
- Jupyter-style notebooks. For ML/data products, Google Colab, Kaggle Kernels, Databricks notebooks, Hex serve as the equivalent of code sandboxes.
- Streamlit, Gradio, Hugging Face Spaces. AI/ML demo-app platforms; effectively code sandboxes optimised for showing AI models in action.
Effect on product evaluation
Removing local installation, repository setup, and configuration reduces the work required to evaluate a product. Stripe and Algolia embed runnable examples in their documentation to shorten that path.
Use embedded sandboxes when browser execution can represent the product accurately and safely.