OpenAI-compatible · Free tier · No cold starts

The AI API that picks the best model for you

Drop-in replacement for the OpenAI API. Use model: "auto" and ZeroOptimize™ routes every request to the best free AI model available — Gemini 2.5 Flash, Llama 4, DeepSeek R1.

Get free API key Read the docs

cURL

Python

JavaScript

from openai import OpenAI

client = OpenAI(
    base_url="https://zerolimitai.com/api/v1",
    api_key="YOUR_API_KEY",
)

response = client.chat.completions.create(
    model="auto",           # ZeroOptimize™ picks the best free model
    messages=[{"role": "user", "content": "Hello!"}],
)

print(response.choices[0].message.content)

model: "auto"→ZeroOptimize™ picks the best free model automatically

200+

AI models available

< 2 lines

migration from OpenAI

24h

model refresh cycle

free tier, forever

Get started in minutes

If you already use the OpenAI SDK, it's literally 2 lines.

cURL

curl https://zerolimitai.com/api/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "auto",
    "messages": [{"role": "user", "content": "Hello!"}]
  }'

Chat with an agent (with memory)

# Chat with a persistent AI agent (with memory)
curl -X POST https://zerolimitai.com/api/v1/chat \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "agentId": "YOUR_AGENT_ID",
    "messages": [{"role": "user", "content": "What do you remember about my project?"}]
  }'

JavaScript / TypeScript

import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://zerolimitai.com/api/v1",
  apiKey: "YOUR_API_KEY",
});

const response = await client.chat.completions.create({
  model: "auto",   // ZeroOptimize™ picks the best free model
  messages: [{ role: "user", content: "Hello!" }],
});

console.log(response.choices[0].message.content);

Full API reference

Everything you need in production

Not just a proxy — a full developer platform.

ZeroOptimize™ auto-routing

Use model: "auto" and our algorithm picks the best available free model for every request — no guessing, no outages, no stale model IDs.

OpenAI-compatible

Change base_url and api_key. Nothing else. Every app built on the OpenAI SDK works with ZeroLimitAI out of the box.

Models updated daily

ZeroOptimize™ re-evaluates the model landscape every 24h. Your API always routes to the current best — without you touching a line of code.

Streaming SSE

Full server-sent events streaming, identical to OpenAI's format. Stream responses in real-time with any SSE-compatible client.

Webhooks

Receive real-time events (message.created, agent.created) with HMAC-SHA256 signed payloads — ready for Zapier, Make, or your own backend.

Secure & private

Your data is never used to train models. API keys are bcrypt-hashed. Bearer token auth, per-key rate limiting, full audit log.

Usage dashboard

Track requests, tokens in/out, estimated cost, and per-model breakdown — today and month-to-date.

Embed widget

Drop an AI chat widget on any website with a single <iframe>. Connect it to any of your agents. No backend needed.

ZeroOptimize™

Stop hardcoding model names.
Let the algorithm decide.

Every 24 hours, ZeroOptimize™ benchmarks available free models using LMSYS Arena ELO scores, context window, parameter count, and live availability. Your calls are automatically routed to the winner — with automatic fallback if it goes down.

Always the best model without code changes
Automatic failover — zero downtime for your app
Free models updated daily (Gemini, Llama, DeepSeek, Qwen…)
Or specify any model explicitly — full control

# Today's ZeroOptimize™ routing

1. gemini-2.5-flash1342 ELOACTIVE

2. llama-4-scout1298 ELO

3. qwen3-235b1287 ELO

4. deepseek-r11271 ELO

5. gemma-3-27b1243 ELO

Updated daily · auto-failover to rank 2 if rank 1 is down

Simple API pricing

Start free. Scale when you need to.

Lifetime Core

$49one-time

API access included. Perfect for side projects and small apps.

2,000 calls/dayBest free models via ZeroOptimize™

2,000 API calls/day
All ZeroOptimize™ free models
OpenAI-compatible endpoint
Streaming (SSE) support
Usage dashboard
Unlimited chat + 40 images/day
2 custom AI agents
30-day money-back guarantee

Get Lifetime Core

Best value

Lifetime Pro

$99one-time

5× more API capacity + the full ZeroLimitAI platform.

10,000 calls/dayAll models incl. paid (GPT-4o, Claude Sonnet)

10,000 API calls/day
All models — free + premium
Webhooks (5 endpoints)
Embed widget for any site
Unlimited chat + 100 images/day
5 custom AI agents
Developer dashboard
30-day money-back guarantee

Get Lifetime Pro

Business

$79/month

or $599/year billed yearly

For production apps at scale with SLA and priority support.

100,000 calls/dayAll models + priority routing

100,000 API calls/day
All models — free + premium
Priority model routing
Dedicated support (< 4h response)
99.9% uptime SLA
Unlimited webhooks
Custom rate limits on request
Usage analytics export

All paid plans include the OpenAI-compatible endpoint, usage dashboard, and ZeroOptimize™ auto-routing. Both Lifetime plans are one-time payments — no recurring fees, ever. Business plan billed monthly or yearly.

FAQ

Is model: "auto" really free?

Yes. When you use model: "auto", ZeroOptimize™ routes your request to the highest-ranked free AI model available at that moment — Gemini 2.5 Flash, Llama 4 Scout, DeepSeek R1, and others. These models are offered free by their providers via open APIs. You pay $0 per call on the free tier.

Do I need a credit card for the free tier?

No. Sign up with email or Google, generate your API key, and start making calls — no credit card required.

Is the API really OpenAI-compatible?

Yes. We expose /api/v1/chat/completions with the exact same request and response format as OpenAI. Any library that supports a custom base_url works — openai-python, openai-node, LangChain, LlamaIndex, and more.

What models are available?

Free tier: Gemini 2.5 Flash, Llama 4 Scout, DeepSeek R1, and whichever model tops the LMSYS rankings at that moment. Lifetime Pro and Business: all free models plus GPT-4o, Claude Sonnet, Gemini Pro, and more. Use GET /api/v1/models to list everything available for your plan.

How does ZeroOptimize™ choose the model?

Every 24h, we benchmark available free models using LMSYS Chatbot Arena ELO scores, parameter count, context window, and live availability. Requests are routed to the top-ranked model. If it fails or rate-limits, the next best is tried automatically — no downtime for your app.

What's the difference between Lifetime Pro and Business?

Lifetime Pro ($99 once) is a one-time payment covering 10k calls/day — ideal for individual developers and small apps. Business ($79/month) gives 100k calls/day, priority routing, a formal SLA, and dedicated support — ideal for startups with real user traffic.

Can I specify a model instead of using auto?

Yes. You can pass any model ID (e.g., "gemini-2.5-flash", "llama-4-scout", "deepseek-r1") instead of "auto". Use GET /api/v1/models to see what's available for your plan.

What happens when I hit the daily limit?

Requests return HTTP 429 with a Retry-After header. Daily limits reset at midnight UTC. Upgrade to a higher plan for more calls, or contact us for custom limits on the Business plan.

Start building in 2 minutes