OpenAI Codex vs Gemini CLI
Detailed comparison of features, performance, and use cases
96/100
OpenAI Codex
OpenAI's flagship agentic coding platform combining Codex Web (autonomous cloud agent powered by o3) and Codex CLI (open-source local tool using GPT-5), delivering end-to-end software development with PR automation and multimodal input support.
Quick Verdict
OpenAI Codex excels at autonomous development and pr automation with a score of 96/100. OpenAI Codex has emerged as a legitimate Claude Code challenger, with GPT-5.
86/100
Gemini CLI
Google's open-source terminal AI agent bringing Gemini directly to your command line with built-in tools for search, file operations, shell commands, and MCP extensibility—free tier included.
Quick Verdict
Gemini CLI excels at terminal-first workflows and free ai coding with a score of 86/100. Gemini CLI democratizes AI-assisted terminal workflows with a generous free tier that rivals paid alternatives.
📊 Visual Score Comparison
Side-by-side comparison of key performance metrics across six evaluation criteria
Technical Specifications
| Feature | OpenAI Codex | Gemini CLI |
|---|---|---|
| Core AI Model(s) | Codex Web uses specialized o3 optimized for coding. Codex CLI uses GPT-5 by default with support for GPT-5.1-Codex-Mini for extended local usage. | Gemini 3 Pro (most intelligent, 1M context), Gemini 3 Flash (fast, 78% SWE-bench). Configurable model selection. |
| Context Window | Large context via o3/GPT-5. Repository preloading enables full codebase understanding without manual file selection. | 1M tokens with Gemini 3 Pro for massive codebase understanding. |
| Deployment Options | Codex Web runs in OpenAI's cloud sandboxes. Codex CLI is open-source and runs locally. Enterprise deployment options available. | npm install -g @google/gemini-cli. Open-source for self-hosting and modification. |
| Offline Mode | Codex CLI supports local execution. Codex Web requires internet for cloud sandbox operation. | Cloud-based, requires internet for model inference. Local tools can execute offline. |
Core Features Comparison
OpenAI Codex Features
- Dual-mode operation: Codex Web (cloud sandbox) and Codex CLI (local execution)
- Autonomous task execution running 1-30 minutes independently in cloud sandboxes
- Auto-review PRs with semantic understanding beyond static analysis
- Multimodal inputs: screenshots, diagrams, and images for context
- MCP (Model Context Protocol) integration for external tools
- Open-source CLI under permissive license
- Repository preloading for full codebase understanding
Gemini CLI Features
- Free tier: 60 requests/min, 1000 requests/day with personal Google account
- Gemini 3 Pro and Flash models with 1M token context
- Built-in tools: Google Search grounding, file ops, shell commands, web fetch
- MCP (Model Context Protocol) for custom integrations
- ReAct loop for complex multi-step reasoning
- Open-source under Apache 2.0 license
- VS Code Gemini Code Assist integration
Pricing & Value Analysis
| Aspect | OpenAI Codex | Gemini CLI |
|---|---|---|
| Pricing URL | View OpenAI Codex Pricing | View Gemini CLI Pricing |
| Overall Score | 96/100 | 86/100 |
| Best For | Autonomous Development, PR Automation, ChatGPT Ecosystem, Multimodal Coding, Enterprise Teams | Terminal-First Workflows, Free AI Coding, Google Ecosystem Integration, Extensible Automation, Large Context Tasks |
Best Use Cases
OpenAI Codex Excels At
- Autonomous feature implementation: describe the task, Codex works independently in a cloud sandbox for up to 30 minutes, then returns completed code with PR
- Automated PR review: tag Codex on any PR for semantic review that understands intent, runs tests, and catches bugs beyond static analysis
- Multimodal debugging: share screenshots of UI bugs or architecture diagrams—Codex interprets visual context to understand and fix issues
- Codebase exploration: ask questions about unfamiliar repositories, Codex navigates and explains code structure with full context
Gemini CLI Excels At
- Free AI coding assistance with generous rate limits for individual developers and small teams
- Large codebase understanding with 1M token context—analyze entire repositories without truncation
- Extensible automation by connecting Figma, Stripe, Datadog, and other tools via MCP integrations
Performance & Integration
| Category | OpenAI Codex | Gemini CLI | Winner |
|---|---|---|---|
| IDE Support | IDE-agnostic via CLI. Integrates with GitHub for PR workflows. ChatGPT desktop and web interfaces. | Terminal-native, IDE-agnostic. VS Code integration via Gemini Code Assist. | Tie |
| Community | Active community | Active community | Tie |
| Data Richness | Comprehensive | Comprehensive | Tie |
| Overall Score | 96/100 | 86/100 | OpenAI Codex |
The Bottom Line
Both OpenAI Codex and Gemini CLI are capable AI coding tools, but they serve different needs. OpenAI Codex scores higher (96/100 vs 86/100) and excels in autonomous development and pr automation. The choice depends on your specific workflow, team size, and technical requirements.
Choose OpenAI Codex if: you prioritize autonomous development and pr automation and want the higher-rated option (96/100).
Choose Gemini CLI if: you prioritize terminal-first workflows and free ai coding and don't mind a slightly lower score for specialized features.