I've been testing o3-pro for a couple weeks now and wanted to share what I've learned. Figured it might help others trying to decide if it's worth the cost.
What is it?
Basically OpenAI's heavy-duty version of o3. It uses more compute during the "thinking" phase, so it's slower but more accurate on hard problems. Came out around June 2025.
Main specs:
200k context
Up to 100k output tokens
Knowledge cutoff June 2024
Takes text and images, outputs text
No image generation or Canvas in ChatGPT
Two ways to access
ChatGPT Pro – $200/month. You get access through the model picker. Good if you just want to use it manually for research, coding, writing. No coding needed.
API – Only through the Responses API, not the regular chat completions. Built for multi-turn stuff and longer tasks. Some requests take minutes so background mode is recommended.
Pricing
API:
$20 per 1M input tokens
$80 per 1M output tokens
Expensive, but about 87% cheaper than old o1-pro pricing.
For reference:
Base o3: $2 input / $8 output
GPT-5.5: around $5 input / $30 output
So o3-pro is definitely not an everyday model.
Where it's good
From what I've seen and read:
Complex coding tasks
PhD-level science/engineering
Strategic planning
Multi-step reasoning that trips up cheaper models
Experts preferred it over base o3 about 56-64% of the time in tests. Not a huge gap but meaningful for critical work.
**
Quick comparison**
o3-pro – Slowest, most expensive, most reliable. Use when being wrong costs more than waiting.
o3 – Much cheaper now. Sweet spot for most devs.
GPT-5.5 – Newer, bigger context, faster. Better default for most people.
For 90% of use cases, start with o3 or GPT-5.5 and only upgrade to o3-pro if you keep hitting quality issues.
Who should pay?
ChatGPT Pro – Good for researchers, analysts, writers who want top-tier access without API hassle.
API – Worth it if you're building automation, agents, or internal tools. o3-pro is for narrow cases where reliability is critical.
Honestly, GPT-5.5 is probably more future-proof for most work given the larger context window. o3-pro is specialized.
On API access
If you're going the API route and want to try multiple models without managing separate keys, I've used a service called CometAPI. Same OpenAI-compatible SDK, just change the base URL, and you can switch between o3-pro, o3, GPT-5.5, Claude, etc. through one key. Pricing was slightly cheaper in my experience. There are other similar services too – definitely compare based on your needs.
Bottom line
o3-pro is impressive but niche. Most people will be better off with o3 or GPT-5.5 for daily use.
If you're unsure, grab a small API budget, test on your actual use case, and see if the extra cost is worth it for your specific tasks.
Curious if others have been using o3-pro heavily – worth it or overkill for you?
