OpenAI O4 Mini vs O3 Mini — Superseded by the GPT-5 Era
🚀 OpenAI's frontier has moved on
O4 Mini and O3 Mini are legacy reasoning models. OpenAI's current line is the GPT-5.x generation, led by GPT-5.3-Codex for agentic coding. For the current model, see the GPT-5.3-Codex overview →
The Original Comparison (For Reference)
When this comparison was written, O4 Mini and O3 Mini were OpenAI's compact reasoning models, each aimed at slightly different needs:
O4 Mini
- Fast and cost-efficient reasoning — a smaller, optimized model
- 99.5% on AIME 2026 benchmark
- Strong non-STEM support, especially data science
- Higher usage limits than O3 Mini
O3 Mini
- Advanced reasoning — OpenAI's most capable compact reasoning model at launch
- Built-in tools — web search and Python within ChatGPT
- Mathematical reasoning and complex problem-solving
- Standard usage limits
Feature summary (legacy)
| Feature | O4 Mini | O3 Mini |
|---|---|---|
| Headline benchmark | 99.5% AIME 2026 | High on ARC-AGI |
| Non-STEM tasks | Excellent | Moderate |
| Speed | Fast, cost-effective | Slower, reasoning-optimized |
| Usage limits | Higher | Standard |
Why This Comparison Is Now Outdated
OpenAI's model line did not stay still. The reasoning-focused "o-series" mini models have been overtaken by the GPT-5.x generation, which unifies frontier reasoning and coding in unified models:
| Legacy (this page) | Current generation | What changed |
|---|---|---|
| O4 Mini / O3 Mini | GPT-5.x line | Reasoning + coding unified; far stronger benchmarks |
| (no coding-specialist mini) | GPT-5.3-Codex | OpenAI's most capable agentic coding model, announced Feb 5 2026 |
GPT-5.3-Codex highlights:
- Frontier coding performance — state-of-the-art on SWE-Bench Pro, Terminal-Bench 2.0, and OSWorld-Verified
- 25% faster than its GPT-5.2-Codex predecessor
- Agentic — handles complex, long-running tasks end-to-end
- Unified — combines the reasoning of the GPT-5 line with specialized coding ability
- Accessible via Codex desktop app, plugins, and API
If you were choosing between O4 Mini and O3 Mini for reasoning or coding work, the practical answer today is to look at the GPT-5.x line instead.
Current Guide
➡️ GPT-5.3-Codex: OpenAI's Most Capable Agentic Coding Model — capabilities, features, benchmark results, and access methods.
Still Using O4 Mini / O3 Mini (Legacy)?
If you're on the legacy mini reasoning models for cost or compatibility reasons, the short version is:
- Pick O4 Mini for fast, cost-efficient reasoning with higher usage limits and strong data-science support.
- Pick O3 Mini for the deepest reasoning with built-in web search and Python tools.
⚠️ These models are no longer OpenAI's frontier. For new work, evaluate GPT-5.3-Codex and the broader GPT-5.x line.