10 best CodeSandbox alternatives in 2026

The cloud development space has moved beyond simple frontend playgrounds.

This article evaluates the best CodeSandbox alternatives in 2026 based on their execution speed, security models, and suitability for both human developers and AI agents.

CodeSandbox is a browser-based development environment designed for writing and running web applications without local setup.

It combines a code editor with a preview window, making it a common choice for reproducible bug reports and sharing frontend components. The platform is built primarily for frontend prototyping with frameworks like React, Vue, and Angular.

CodeSandbox serves multiple purposes across different developer workflows:

• Creating shareable code examples for documentation and tutorials that others can view and fork
• Reproducing bugs in clean, isolated environments accessible via link
• Live coding during technical interviews or presentations where viewers see code and output simultaneously
• Prototyping AI-generated code in browser-based sandboxes
• Backend development through "Devboxes," though the platform's core strength remains frontend experimentation

It's no longer just developers looking for cloud editors. AI engineers and DevOps teams are searching for alternatives to address specific technical friction:

• Cold starts and latency: Large containers can take significant time to boot, which breaks the flow when you need instant feedback.
• Session limitations: Most browser-based environments terminate processes once the tab is closed. This is incompatible with long-running AI tasks or background jobs that need to persist beyond a single browser session.
• Execution isolation: Running untrusted code requires hardened security layers that basic sandboxes often lack. If you're building AI coding assistants or allowing users to execute arbitrary code, you need microVM-level isolation, not just containerization.

Traditional sandboxes are built for ephemeral testing, which creates constraints for professional workflows:

• Ephemeral storage: Data is often lost between restarts, making stateful development difficult. If your application needs to maintain state or store user data, you'll hit these limits quickly.
• Networking constraints: Exposing multiple ports or managing complex microservice communication within a browser tab becomes challenging. Most sandboxes are designed for single-service prototypes, not distributed systems.
• Resource overhead: High CPU and memory overhead for simple tasks compared to optimized microVMs. Browser-based environments need to run the editor, preview, and your application simultaneously, which adds unnecessary load.

If you need instant feedback for UI experiments and component demos, these platforms offer the fastest path from idea to shareable prototype.

StackBlitz runs Node.js in your browser using WebContainers, which eliminates the need for remote VMs. The platform supports offline work after the initial load.

Best for:

• Angular, React, and npm-based projects
• Frontend prototyping without infrastructure setup
• Sharing reproducible environments via URL
• Developers who need offline capability

Replit provides a collaborative full-stack environment with AI assistance through Ghostwriter. The platform includes multiplayer features for real-time collaboration.

Best for:

• Pair programming and teaching scenarios
• Full-stack applications with frontend and backend
• Teams using AI-assisted coding with collaboration
• Educational use cases and coding interviews

CodePen is a frontend-focused playground for HTML, CSS, and JavaScript with real-time preview.

Best for:

• UI component demonstrations
• CSS animations and visual effects
• Shareable code demos
• Frontend-only projects and experiments

Glitch focuses on community features and project remixing. You can fork public projects and the platform handles deployment automatically.

Best for:

• Community-driven projects and learning
• Web app prototypes with deployment
• Remixing existing projects
• Social coding features

For teams that need full development environments with repository integration and standardized setups, these platforms provide VS Code-like experiences in the cloud.

Codespaces provides a VS Code instance in the cloud, connected to your GitHub repositories. Environment configuration uses devcontainer.json for team consistency.

Best for:

• Teams using GitHub for version control
• Projects requiring consistent development environments
• Workflows with GitHub Actions and pull requests
• Repository-to-environment workflows

Gitpod creates ephemeral dev environments based on Git branches and can generate preview environments for pull requests.

Best for:

• Review workflows requiring environment access
• Teams wanting automated preview environments
• Organizations needing self-hosted options
• Git-based development workflows

If you're building AI coding assistants, educational platforms, or any service that needs to run user-generated code, you need more than a traditional sandbox. You need programmatic access, robust isolation, and APIs designed for automation. Learn more about choosing the best code execution sandbox for AI agents.

E2B provides isolated environments controlled via API with SDKs for Python, TypeScript, and JavaScript. The platform includes configurable timeout and resource limits.

Best for:

• AI coding assistants and agents
• Programmatic code execution via API
• Educational platforms requiring code sandboxing
• Applications needing isolated execution environments
• For more context on AI sandbox platforms, check out our guide on top AI sandbox platforms for code execution

Modal handles Python workloads for ML and data processing. You define functions in Python and the platform manages infrastructure including GPU allocation and scaling.

Best for:

• ML inference and training jobs
• Batch processing and data pipelines
• Python-based API endpoints with GPU access
• Serverless Python workloads
• See how Modal compares in our Modal sandboxes alternatives guide

Val.town turns functions into API endpoints or scheduled jobs. The platform includes social features for browsing and forking other users' code.

Best for:

• Scripts and personal automation projects
• Learning from community examples
• Function-based API endpoints
• Social coding and function sharing

Northflank is not a browser IDE. You write code in your preferred editor and use Northflank as the secure execution layer and production infrastructure.

With CodeSandbox or StackBlitz, you write and run code in the same environment. Northflank separates these concerns:

• Your developers use local IDEs or cloud editors for writing code
• Northflank handles execution, particularly for untrusted or AI-generated code
• Code runs isolated at the VM level, not just process level
• Uses microVM technologies like Firecracker, gVisor, and Kata Containers

This architecture matters for AI coding tools. When your AI agent generates code, you need isolation at the VM level to prevent untrusted code from accessing your application logic.

Traditional containers share the kernel with the host OS, creating security risks. MicroVMs provide hardware-level isolation:

• Each sandbox gets its own kernel
• Arbitrary user code runs without risking your infrastructure
• Hardware-level isolation prevents container breakout attacks
• Critical for platforms allowing custom scripts, model training, or AI-generated code execution

Learn more about Northflank's microVM implementation for secure sandboxing.

Northflank supports persistent volumes and managed databases for production workloads:

• Applications stay online 24/7 with production uptime guarantees
• No session limits or sleeping apps
• Persistent storage for stateful applications
• Managed databases integrated with your execution environment

You can start with a sandbox for testing AI-generated code, then promote the same environment to production without platform migration.

Northflank eliminates the distinction between prototyping and production infrastructure:

• Same platform for secure code execution and application hosting
• Supports databases, APIs, and frontend applications
• No need to rebuild on different platforms
• Single infrastructure for both sandbox testing and production deployment