Codex CLI vs GPT-5.1
A detailed comparison to help you choose the right AI tool for your needs.
Feature Comparison
Feature
Codex CLI
GPT-5.1
Ratings
Overall Rating
4.7
4.7
Coding
4.7
4.5
Writing
4.3
4.6
Reasoning
4.5
4.8
Speed
4.6
4.8
Value
4.8
4.6
Pricing
Monthly Price
$20
$20
Free Tier
Input (per 1M tokens)
$2.5
$2.5
Output (per 1M tokens)
$10
$10
Features
Context Window
128K
128K
Vision/Images
Audio
Video
Code Generation
AI Agents
Codex CLI
Pros
- Open source (Apache 2.0)
- Multimodal input support
- Local-first privacy
- Rich approvals workflow
- Included with ChatGPT subscription
Cons
- Newer tool with evolving features
- Less mature than Claude Code
GPT-5.1 Instant
Pros
- Fast responses with adaptive reasoning
- New personalization presets
- Strong math and coding improvements
- Multimodal (text, image, audio)
- Free tier available
Cons
- Coding not as strong as Claude Opus
- Can be verbose
- Writing style less natural than Claude
Choose Codex CLI if you need:
Rapid prototyping, open-source flexibility, ChatGPT users
Choose GPT-5.1 if you need:
General assistant, math problems, quick coding help
Ready to get started?
Both tools offer free tiers or trials. Try them out and see which one works best for your workflow.