Free OpenAI-Compatible API: Best Options 2026

Last updated: June 2026

Key takeaways

• A "free OpenAI-compatible API" is a service exposing the OpenAI Chat Completions request/response shape that you can call without paying, so the same SDK and code work by changing only base_url and the API key.
• Speka offers a $0/month Free plan with $1 of included usage, no credit card, 10 requests per minute, and 1 API key — enough to evaluate 16 production models against a real workload.
• Hugging Face's open-source Text Generation Inference (TGI) is free to self-host and exposes an OpenAI-compatible Messages API; the hosted Inference free tier is rate-limited and credit-gated, not unlimited.
• OpenRouter publishes a catalog of free models (roughly 26–28 as of June 2026) with low rate limits; Together AI gives one-time signup credit whose amount varies by promo — treat both as trials, not perpetual free tiers.
• "Free" almost always means one of three things: limited monthly usage, low rate limits, or self-hosting where you pay for the GPU. Read the caveats before you build on it.

What is a free OpenAI-compatible API?

A free OpenAI-compatible API is an inference endpoint that accepts the same request format as OpenAI's Chat Completions API and returns the same response shape, while letting you start without payment. Because the contract is identical, the official OpenAI Python SDK and most frameworks work as drop-in clients — you change base_url to the provider's /v1 endpoint and supply that provider's key. "Free" is not one thing: it can mean a monthly usage allowance (Speka), a self-hostable open-source server where you supply hardware (TGI, vLLM, SGLang), or a catalog of free-but-rate-limited models on a gateway (OpenRouter). The right choice depends on whether you need zero-cost evaluation, zero-cost hosting, or zero-cost production traffic.

Why does OpenAI compatibility matter?

OpenAI's Chat Completions schema became the de facto interface for LLM inference. Standardizing on it means your application code, retries, streaming parser, and tool-calling logic stay the same across providers. Switching vendors becomes a configuration change, not a rewrite — which also protects you from lock-in.

Compatibility also means the ecosystem already works. LangChain's ChatOpenAI, LlamaIndex, and n8n can all point at any OpenAI-compatible base URL. Streaming uses Server-Sent Events, and authentication follows the standard Bearer token header. If a provider gets these details right, "compatible" is real rather than marketing.

Which providers offer a genuine free tier in 2026?

The table below compares the practical free-start options. Figures are dated June 2026 and competitor free amounts are hedged because they shift with promos and policy — always confirm on the provider's own signup page.

Provider	Free to start?	What "free" means	Rate limit (free)	Card required	OpenAI-compatible
Speka	Yes	$0/mo plan, $1 usage included monthly	10 req/min, 1 key	No	Yes (/v1, drop-in)
Hugging Face TGI (self-host)	Yes (software)	Free open-source server; you pay for GPU	Your hardware	No (for software)	Yes — Messages API
Hugging Face hosted Inference	Yes (trial-style)	Rate-limited free usage, credit-gated	Provider-set, low	Varies	Partial/Yes
OpenRouter	Yes	Catalog of free models (~26–28, Jun 2026)	~20 req/min + daily cap	No (for free models)	Yes (drop-in)
Together AI	Yes (one-time)	Signup credit; amount varies by promo	Account-tier limits	No	Yes (/v1)
vLLM / SGLang (self-host)	Yes (software)	Free open-source server; you pay for GPU	Your hardware	No (for software)	Yes

A few clarifications so the table isn't misread:

• Speka is the only row here offering a perpetual zero-dollar plan with a fresh monthly usage allowance and no card. The $1 included usage resets monthly; see the pricing page for exact plan details.
• OpenRouter is fully OpenAI-compatible and documented as a drop-in for the OpenAI SDK. Its free models (e.g. open-weight DeepSeek and Qwen variants as of June 2026) carry low rate limits — commonly cited around 20 requests/minute with a daily cap tied to your credit balance. The exact roster and limits change; verify on OpenRouter.
• Together AI is OpenAI-compatible at https://api.together.ai/v1, but its free allotment is a one-time signup credit. Sources have reported anywhere from ~$1 historically to ~$25 in more recent 2026 promos — treat the amount as "varies, verify on signup." There is no confirmed perpetually-free unlimited tier.
• TGI, vLLM, and SGLang are free as software. The TGI Messages API, the vLLM OpenAI-compatible server, and SGLang all expose /v1/chat/completions. The catch is operational: you provide the GPU, model weights, scaling, and uptime. "Free inference" here means a free server, not free compute. Ollama is the lightweight local equivalent, with its own OpenAI compatibility layer.

How realistic are "free" rate limits?

Free tiers are gated on three axes, and you should plan for whichever you hit first:

1. Requests per minute (RPM). Speka's Free plan is 10 RPM. OpenRouter free models are commonly ~20 RPM. These are fine for prototyping, a single developer, or a low-traffic side project, but not for a chatty production app fanning out concurrent requests.
2. Monthly usage allowance. Speka's $1/month covers a meaningful amount of evaluation — for example, the inexpensive Llama 3.1 8B at $0.05 per 1M input and output tokens stretches a long way for testing prompts. Once you exceed it, you move to standard per-token rates with no overage penalties.
3. Daily caps and credit balance. Gateways like OpenRouter often tie free-model daily caps to your account's credit balance, so "free" usage can quietly shrink as balances change.

The honest summary: free tiers are sized for evaluation and light use. If your traffic is bursty or concurrent, you'll hit RPM limits before you exhaust token allowances. Budget for a paid tier — Speka's Starter is $19/month with $25 included and 60 RPM — once you move past prototyping.

How do I call a free OpenAI-compatible API? (Speka example)

Speka's base URL is https://speka.me/v1 and keys are prefixed sk-speka-live-.... Create a key on the signup page, then point any OpenAI client at it.

cURL:

curl https://speka.me/v1/chat/completions \
  -H "Authorization: Bearer sk-speka-live-..." \
  -H "Content-Type: application/json" \
  -d '{
    "model": "meta/llama-3.3-70b-instruct",
    "messages": [
      {"role": "user", "content": "Explain rate limiting in one sentence."}
    ],
    "stream": false
  }'

Python (OpenAI SDK):

from openai import OpenAI

client = OpenAI(
    base_url="https://speka.me/v1",
    api_key="sk-speka-live-...",
)

resp = client.chat.completions.create(
    model="deepseek-ai/deepseek-v4-flash",
    messages=[{"role": "user", "content": "Write a haiku about API gateways."}],
)
print(resp.choices[0].message.content)

That's the entire migration: change base_url, change the key, keep your code. Streaming (stream=True), JSON mode, native tool/function calling, and embeddings all use the same OpenAI-shaped parameters. The same swap works for LangChain's ChatOpenAI and LlamaIndex by setting their OpenAI base URL.

What can you actually build on Speka's free tier?

Speka's catalog is 16 frontier models from 7 labs — DeepSeek, NVIDIA, Meta, Mistral AI, Moonshot AI, OpenAI, and Black Forest Labs — and the free plan can reach all of them. Some real model IDs and list prices (per 1M tokens, input/output):

Model	ID	Use	Price (in/out)
DeepSeek V4 Flash	deepseek-ai/deepseek-v4-flash	reasoning, 128K	$0.27 / $1.10
Llama 3.3 70B	meta/llama-3.3-70b-instruct	chat, 128K	$0.20 / $0.20
Llama 3.1 8B	meta/llama-3.1-8b-instruct	cheap chat	$0.05 / $0.05
Kimi K2.6	moonshotai/kimi-k2.6	chat	$0.50 / $2.00
GPT-OSS 120B	openai/gpt-oss-120b	code	$0.15 / $0.60
NV-EmbedQA E5 v5	nvidia/nv-embedqa-e5-v5	embeddings	$0.01 / 1M
FLUX.1 [dev]	image	image gen	$0.04 / image

These are real hosted models — the underlying weights are public, e.g. Llama 3.3 70B, the DeepSeek org, GPT-OSS 120B, and FLUX.1-dev — served behind one OpenAI-compatible endpoint. With $1/month you can benchmark a reasoning model, an embeddings model, and an image model against your own data before committing a cent. Models from Mistral AI, NVIDIA NIM, and Black Forest Labs round out the catalog. Browse the full list and per-model docs in the model catalog and API docs.

Frequently asked questions

Is there a truly free OpenAI-compatible API with no credit card?

Yes. Speka's Free plan is $0/month with $1 of included usage, 10 requests per minute, and one API key, and it requires no credit card. The usage allowance resets monthly, so you can keep evaluating models without paying. Open-source servers like TGI and vLLM are also free as software, though you supply the GPU to run them.

What's the difference between a free hosted API and self-hosting?

A free hosted API (like Speka's Free plan) gives you a managed endpoint with an included usage allowance — no infrastructure to run. Self-hosting with TGI, vLLM, or SGLang means the software is free but you provision and pay for the GPU, scaling, and uptime yourself. Hosted is faster to start; self-hosting can be cheaper at high, steady volume if you already operate GPUs.

How accurate are competitors' free-tier claims for 2026?

They shift often, so hedge. OpenRouter publishes a catalog of free models (roughly 26–28 as of June 2026) with low rate limits around 20 requests per minute plus a daily cap. Together AI offers one-time signup credit whose dollar amount varies by promo (reported from ~$1 historically to ~$25 in 2026). Always confirm current figures on each provider's own signup or pricing page before relying on them.

Can I use the OpenAI Python SDK with a free API?

Yes. Any OpenAI-compatible provider works with the official OpenAI Python SDK by setting base_url to the provider's /v1 endpoint and passing that provider's key. For Speka, use base_url="https://speka.me/v1" and a sk-speka-live-... key. Streaming, JSON mode, tool calling, and embeddings use the same parameters, so existing OpenAI code runs unchanged.

What happens when I exceed the free usage allowance?

On Speka, exceeding the $1 monthly included usage moves you to standard per-token rates with no overage penalties — you simply pay the listed price for the extra tokens. On gateways with free-model catalogs, you typically hit a rate limit or daily cap rather than a charge, and requests are throttled or rejected until the window resets or you add credit.

Do free tiers support tool calling and image generation?

On Speka, yes — the Free plan reaches every catalog feature: native tool/function calling, JSON mode, streaming, embeddings, and image generation via FLUX models. Coverage on other platforms is model-dependent: OpenRouter and Together AI support tool calling only for models whose underlying provider implements it, and image generation is limited to specific image models. Check each model's capability flags before depending on a feature.

Try it on Speka

If you want a free OpenAI-compatible API you can use today without a credit card, create a Speka account and grab a sk-speka-live-... key. Point your existing OpenAI SDK at https://speka.me/v1, spend the included $1 testing 16 real models, and upgrade only when your traffic outgrows the free plan limits. Read the API docs to get your first request running in minutes.