What is o3 and how is it different from GPT-4o

o3 is OpenAI's reasoning model (Reasoning Model). The key differences from GPT-4o:

o3 performs an "internal chain of thought" before answering, enabling deeper reasoning for complex problems

Longer response time (15-45 seconds vs. GPT-4o's 1-3 seconds)

Significantly stronger in math, programming, and scientific reasoning

Higher cost (about 10x that of GPT-4o)

The 20 Best Tasks for o3

Math and Logic (strongest scenarios):

Math competition problems (AIME level, scoring 96.7%)

Multi-step logical deduction

Probability and statistical analysis

Algorithm complexity analysis

Programming (high-value scenarios):

Complex algorithm design

Multi-file code architecture planning

Debugging particularly tricky bugs

Security vulnerability analysis

Analysis and Research:

Causal relationship analysis

Legal contract risk assessment

Medical diagnosis auxiliary reasoning

Scientific research method design

Scenarios not suitable for o3 (o4-mini is better): 13-20. Everyday conversation, content writing, quick queries, creative generation (speed first)

How to Switch to o3 in ChatGPT

Open ChatGPT (requires Plus/Pro subscription)

In a new conversation, click the model selector

Select "o3"

Plus users get about 50 uses per day, Pro users more

Note: o3 supports image input but does not support DALL-E image generation

API Usage

python
from openai import OpenAI
client = OpenAI()
Basic usage
response = client.chat.completions.create(
    model="o3",
    messages=[{"role": "user", "content": "Analyze three ways to solve this math problem: ..."}],
    max_completion_tokens=8000
)
print(response.choices[0].message.content)
Control reasoning depth (save costs)
response = client.chat.completions.create(
    model="o3",
    messages=[{"role": "user", "content": "..."}],
    reasoning_effort="low"  # low/medium/high
)

Cost Estimation

Usage MethodEstimate

ChatGPT Plus 20 times per monthFree (included in $20 subscription) API 1K tokens input + 2K output~$0.10 API complex analysis (10K tokens)~$0.60

Best Practices

Don't waste o3 on simple tasks: Use GPT-4o for "help me write an email"

Provide sufficient context: o3 thinks deeper, give it enough information

Accept the waiting time: o3's 30-second wait yields more reliable complex reasoning

Verify important conclusions: Even for o3, manual verification is still needed for high-risk decisions