Key takeaways
- 58K+ GitHub stars — fastest-growing open-source AI coding extension in the VS Code ecosystem
- Human-in-the-loop by design — approve every file change and terminal command before execution
- Model Context Protocol (MCP) support — extend capabilities with custom tools and integrations
FAQ
What is Cline?
Cline is an open-source VS Code extension that provides autonomous AI coding capabilities with human approval for every file change and terminal command.
Is Cline free?
Yes, Cline is free and open source (Apache 2.0). You provide your own API keys for LLM providers like Anthropic, OpenAI, or OpenRouter.
How is Cline different from GitHub Copilot?
Copilot is autocomplete-focused; Cline is an autonomous agent that can create files, run commands, and use the browser — with your approval at each step.
What's the relationship between Cline and Roo Code?
Roo Code forked from Cline and added cloud agents and team features. Cline remains the pure open-source upstream project.
Executive Summary
Cline is an open-source VS Code extension that brings autonomous AI coding to your IDE with a key differentiator: human-in-the-loop approval for every action. With 58,000+ GitHub stars, Cline has become the fastest-growing AI coding tool in the VS Code ecosystem.[1] Originally called "Claude Dev," it supports any LLM provider and has pioneered features like browser automation and MCP tool creation that others have since adopted.
| Attribute | Value |
|---|---|
| Company | Cline Bot Inc. |
| Founded | 2024 |
| Funding | Undisclosed |
| GitHub Stars | 58,000+ |
| License | Apache 2.0 |
Product Overview
Cline (an acronym for "CLI aNd Editor") is a VS Code extension that acts as an AI assistant capable of handling complex software development tasks step-by-step.[2] Unlike autocomplete tools, Cline can create and edit files, run terminal commands, use the browser, and even create new tools — all with your explicit approval at each step.
The human-in-the-loop design is intentional: while autonomous AI agents traditionally run in sandboxed environments, Cline provides a GUI to approve every action, making agentic AI accessible and safe for everyday development.
Key Capabilities
| Capability | Description |
|---|---|
| File Operations | Create, edit, delete files with diff preview |
| Terminal Commands | Execute shell commands and monitor output |
| Browser Automation | Launch browser, click, type, capture screenshots |
| MCP Tools | Create and use custom tools via Model Context Protocol |
| Image Input | Convert mockups to functional apps |
Product Surfaces
| Surface | Description | Availability |
|---|---|---|
| VS Code Extension | Primary interface in the IDE sidebar | GA |
| Cline CLI | Terminal interface for headless workflows | GA |
| Enterprise Edition | SSO, policies, audit trails | Enterprise |
Technical Architecture
Cline runs entirely locally as a VS Code extension.[3] It connects directly to your chosen LLM provider — no intermediate servers see your code or prompts. The extension uses VS Code's shell integration API for terminal monitoring and Playwright for browser automation.
Key Technical Details
| Aspect | Detail |
|---|---|
| Deployment | Local (VS Code extension) |
| Model(s) | Any provider — Anthropic, OpenAI, Gemini, Bedrock, local models |
| Integrations | VS Code, terminal, browser, MCP servers |
| Open Source | Yes (Apache 2.0) |
Browser automation: Using Claude's Computer Use capability, Cline can launch a headless browser to test web apps, capture screenshots, and fix visual bugs.[1]
MCP integration: Cline can create custom tools by generating MCP servers on the fly. Ask "add a tool that fetches Jira tickets" and Cline builds and installs it.
Strengths
- Human-in-the-loop safety — Every action requires explicit approval; safe by design
- Massive adoption — 58K+ stars, one of the most popular VS Code AI extensions
- Browser automation — Built-in capability to test web apps and fix visual bugs
- MCP extensibility — Create custom tools without leaving the workflow
- Multi-provider support — Works with any LLM provider, including local models
- Active development — Rapid feature releases, responsive to community needs
- Enterprise ready — SSO, policies, VPC deployment available[4]
Cautions
- VS Code only — Primary experience limited to VS Code (and compatible forks)
- Token-intensive — Agentic workflows can consume significant tokens
- BYOK required — No free tier; users provide their own API keys
- Fork ecosystem — Multiple forks (Roo Code, others) may fragment community
- Approval friction — Human-in-the-loop can slow down for routine tasks (YOLO mode available but risky)
Pricing & Licensing
| Tier | Price | Includes |
|---|---|---|
| Open Source | Free | Full functionality (Apache 2.0) |
| Enterprise | Custom | SSO, policies, audit trails, support |
Licensing model: Free and open source — you pay your LLM provider directly.
Hidden costs: Complex agentic tasks can consume $5-50+ in API costs per session depending on model and task complexity.
Competitive Positioning
Direct Competitors
| Competitor | Differentiation |
|---|---|
| Roo Code | Fork of Cline with cloud agents; Cline is the upstream open source |
| GitHub Copilot | Copilot is autocomplete; Cline is a full autonomous agent |
| Cursor | Cursor is a full IDE; Cline is an extension for your existing VS Code |
| Aider | Aider is terminal-native; Cline is VS Code-native with GUI approvals |
When to Choose Cline Over Alternatives
- Choose Cline when: You want agentic AI in VS Code with explicit approval for every action
- Choose Roo Code when: You need cloud agents and team collaboration features
- Choose Cursor when: You want an AI-native IDE rather than an extension
- Choose Aider when: You prefer terminal-based workflows with git-native commits
Ideal Customer Profile
Best fit:
- VS Code users who want agentic AI without switching editors
- Developers who value explicit approval over autonomous execution
- Teams needing enterprise security (VPC, SSO, audit trails)
- Web developers who benefit from browser automation
- Power users who want to extend capabilities via MCP
Poor fit:
- Developers who prefer terminal-based workflows
- Teams wanting fully autonomous background agents
- JetBrains users (Sweep is a better option)
- Users seeking a simple autocomplete experience
Viability Assessment
| Factor | Assessment |
|---|---|
| Financial Health | Unknown (Cline Bot Inc. funding not disclosed) |
| Market Position | Leader — Most-starred VS Code AI extension |
| Innovation Pace | Rapid — Pioneered browser automation and MCP in coding agents |
| Community/Ecosystem | Active — Large Discord community, active GitHub[5] |
| Long-term Outlook | Positive — Strong community, enterprise tier provides revenue path |
Cline has achieved remarkable growth in under two years. The fork by Roo Code (1.2M+ installs) validates the approach while creating questions about long-term ecosystem fragmentation.
Bottom Line
Cline is the leading open-source VS Code extension for agentic AI coding. Its human-in-the-loop design makes it accessible to developers who want AI assistance without giving up control, while features like browser automation and MCP extensibility push the boundaries of what coding assistants can do.
Recommended for: VS Code users who want powerful agentic AI with explicit approval for every action and the ability to extend capabilities via custom tools.
Not recommended for: Developers who prefer terminal workflows, want fully autonomous agents, or need JetBrains IDE support.
Outlook: Cline will continue leading the VS Code AI extension space. The enterprise tier suggests a sustainable business model, and the MCP ecosystem will drive continued innovation.
Research by Ry Walker Research • methodology