Cline is a free, open-source VS Code extension that acts as an autonomous coding agent. You bring your own model API key - Claude, GPT, Gemini, or local models - and Cline executes tasks transparently, showing each action before it runs.
Best for: Developers who want an open-source agent, full control over which model powers it, and transparent step-by-step actions - without vendor lock-in.
Not ideal for: Users who want a fully managed, polished commercial experience, or who prefer not to manage their own model API billing.
Cline takes a different path from the commercial AI editors: it is free and open source, and it runs as an extension inside VS Code rather than as its own product. Instead of bundling a model and charging a subscription, Cline asks you to bring your own API key, putting you in direct control of which model powers the agent and what you pay.
Its other hallmark is transparency - Cline shows each action it intends to take before executing it. This review covers how Cline works, what its bring-your-own-key model means for cost and control, and where the open-source approach trades polish for freedom.
What is Cline?
Cline is an open-source autonomous coding agent that runs as a VS Code extension. It can read and edit files, run commands, and work through multi-step tasks, all inside the editor you may already use. Because it is open source, its behaviour is inspectable and it carries no vendor lock-in.
Crucially, Cline is model-agnostic: you supply an API key for the provider of your choice - Claude, GPT, Gemini, or even local models - and Cline uses it. This means your costs are exactly your model usage, with no subscription markup on top.
Key features
- Open source and free The extension itself is free and open source, with inspectable behaviour and no lock-in.
- Bring your own model Use any supported provider - Claude, GPT, Gemini, or local models - by supplying your own API key.
- Transparent, step-by-step actions Cline shows each action before it executes it, so you can approve or correct the agent as it works.
- Runs inside VS Code No separate editor to adopt - it works within your existing VS Code setup.
- Full agentic capability Reads and edits files, runs commands, and completes multi-step tasks across a project.
How it works in practice
You install the extension, add an API key for your chosen model, and give Cline a task. It then works step by step, surfacing each planned action - a file edit, a command to run - for your visibility and approval. This transparency makes it easy to keep the agent on track and to learn what it is doing, which some developers prefer over more opaque tools.
Because you pay your model provider directly, cost control is entirely in your hands: choose a cheaper model for routine work, a frontier model for hard problems, or a local model to avoid API costs altogether. The flip side is that you manage that billing yourself rather than getting a single predictable subscription.
Output and capability
Cline’s capability tracks the model you give it: pair it with a strong frontier model and it performs comparably to commercial agents on many tasks, since the underlying intelligence is the same. Its transparent, approval-based flow can also produce more controllable results than fully autonomous tools.
What it trades is polish. As an open-source project, the experience is less buttoned-up than a commercial product - fewer guardrails, a rougher edge in places - and you take on the setup and billing management yourself. For developers who value control over convenience, that is an acceptable trade.
Limitations to be aware of
The main consideration is that you manage your own model API billing. There is no bundled subscription, so you need an API account with a provider and you pay per usage - which can be cheaper or pricier than a flat plan depending on how heavily you work and which model you choose.
As an open-source tool, Cline is also less polished than commercial alternatives. It is capable, but expect a rougher experience and more self-service than a managed product, and rely on its transparency to keep the agent in check.
Pricing
Cline itself is completely free and open source. Your only cost is the model usage you pay your chosen provider directly, which gives you full control over spend.
| Plan | Price | What it includes |
|---|---|---|
| Cline extension | Free | Open source, no subscription.; Free, open-source VS Code extension; No vendor lock-in; Transparent step-by-step actions; Full agentic capability |
| Model usage | Pay your provider | Bring your own API key.; Use Claude, GPT, Gemini, or local models; Pay the provider directly for usage; Choose cheaper or frontier models per task; Local models can avoid API costs entirely |
Total cost is whatever your chosen model provider charges for usage. Cline also offers a flat $9.99 ClinePass for open coding models. A worked token-cost table is in Cline pricing explained. Using local models can reduce or eliminate API costs. Monitor provider usage to manage spend.
Pros and cons
Pros
- Free and open source, with no vendor lock-in
- Model-agnostic: bring your own key for Claude, GPT, Gemini, or local models
- Transparent, approval-based actions keep you in control
- Runs inside your existing VS Code setup
- Cost control is entirely in your hands
- Capability scales with whichever model you choose
Cons
- You manage your own model API billing
- Less polished than commercial alternatives
- Requires more setup and self-service
- No bundled support of a paid product
Common questions
Is Cline really free?
The Cline extension is free and open source. Your only cost is the model usage you pay your chosen provider directly (for example Anthropic, OpenAI, or Google), or nothing extra if you run local models.
Which models can I use with Cline?
Cline is model-agnostic. You can use frontier models like Claude, GPT, and Gemini by supplying your own API key, or run local models. This lets you match the model to the task and control cost directly.
How is Cline different from Cursor?
Cursor is a polished commercial editor with a bundled subscription and managed models. Cline is a free, open-source VS Code extension where you bring your own model key and approve each action. Cline offers more control and no lock-in; Cursor offers more polish and a managed experience.
Is Cline good for beginners?
Cline is capable but requires setting up your own model API key and managing billing, and it is less polished than commercial tools. Beginners who want a turnkey experience may prefer a managed editor, while those comfortable with some setup will appreciate the control and transparency.
Verdict
Cline is the standout choice for developers who want an open-source agent with full control. By letting you bring your own model and showing every action before it runs, it offers transparency and flexibility that commercial tools generally do not - and the extension itself costs nothing, so you pay only for the model usage you choose.
The trade-off is polish and self-service: you manage your own API billing and accept a rougher experience than a managed product. For developers who value control, transparency, and freedom from lock-in over turnkey convenience, Cline is excellent, and because it is free, it costs nothing but an API key to try.