o3 via the ApexApi gateway
o3 is OpenAI's reasoning model — it thinks step-by-step before answering, excelling at math, science, and hard coding problems where careful, deliberate reasoning matters more than raw speed. Available via ApexApi.
o3 is served through ApexApi's unified, OpenAI-compatible API — one key, one format, with smart routing and automatic failover. Provider: OpenAI.
Why o3
Deliberate reasoning
Thinks through problems step by step for harder tasks.
Math & science
Strong on quantitative and analytical problems.
Hard coding
Tackles complex, multi-step programming challenges.
Specifications
- Modality
- chat
- Context window
- 200K tokens
- Max output
- 100K tokens
- Streaming
- Yes
- Tool / function calling
- Yes
- Vision input
- Yes
o3 pricing
Pay-per-use — no subscription, no minimums. Buy credits and pay only for what you call. Transparent, per-call pricing across every model.
Getting started with o3
OpenAI-compatible — point your client at ApexApi, swap your key, and call it. No new SDK to learn.
from openai import OpenAI
client = OpenAI(
base_url="https://api.apexapi.dev/v1",
api_key="<YOUR_APEXAPI_KEY>",
)
response = client.chat.completions.create(
model="openai/o3",
messages=[{"role": "user", "content": "Hello!"}],
)
print(response.choices[0].message.content)o3 use cases
What teams build with o3 on ApexApi.
Complex problem solving
Math, science, and logic-heavy tasks.
Hard engineering
Algorithmic and multi-step coding problems.
Verification & analysis
Careful checking and reasoning over solutions.
o3 vs other models
How it compares — and on ApexApi you can switch between any of them with a single string change, same key, same endpoint.
o3 vs GPT-5.5
GPT-5.5 is the fast multimodal generalist; o3 trades speed for deeper deliberate reasoning on hard problems.
Learn more about GPT-5.5 API →o3 vs DeepSeek V4 Pro
Both are strong on reasoning/coding; compare depth vs cost on ApexApi.
Learn more about DeepSeek V4 Pro API →Why build on ApexApi
One API, every model
OpenAI-compatible — swap the base URL and key, keep your code. Call 14+ providers and hundreds of models through a single integration.
Smart routing & failover
Per-model provider chains with automatic failover. If one provider degrades, requests route to the next — your app stays up.
Pay-per-use, no lock-in
Buy credits, pay only for what you call. No subscriptions, no minimums. Switch models anytime with a single string change.
o3 API — FAQ
How do I use the o3 API?
Create an ApexApi key, then point your client at https://api.apexapi.dev/v1 and use the model slug. Send a request to /v1/chat/completions with the model slug — the API is OpenAI-compatible, so most OpenAI SDKs work by changing the base URL and key.
Is the o3 API OpenAI-compatible?
Yes. ApexApi exposes o3 through the same OpenAI-compatible interface used across the whole catalog — swap the base URL and API key and keep your existing code.
How much does o3 cost on ApexApi?
Pay-per-use — see the live price in the Pricing section above. There's no subscription or minimum; you buy credits and pay only for what you call.
Can I switch from o3 to another model later?
Yes — change a single string (the model slug) to call any other model in the catalog through the same endpoint and key. No re-integration.
Ready to build with o3?
One API key. Every major AI model. Pay only for what you use.
Get your API key — free to start