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OpenAI API alternatives you can call with OpenAI’s SDK
Anthropic, Google, xAI and DeepSeek all let you use OpenAI’s own SDK with their models: you change the base URL, the API key and the model name. Here’s how each one works, what its models cost next to OpenAI’s, and what doesn’t carry over when you switch.
Checked October 20, 2026 against each company’s compatibility docs · prices checked October 13, 2026
Which APIs work with the OpenAI SDK
| Company | Base URL | OpenAI-style API | API key from | Good to know |
|---|---|---|---|---|
| Anthropic | https://api.anthropic.com/v1/ | Chat Completions | Claude Console | Meant for testing and comparing models; Anthropic says it isn’t a long-term or production-ready solution for most uses. No prompt caching through it. |
https://generativelanguage.googleapis.com/v1beta/openai/ | Chat Completions, plus images, video, embeddings and batch | Google AI Studio | Still in beta, Google says. Gemini-only features, such as its context cache, go in extra_body. | |
| xAI | https://api.x.ai/v1 | Responses (recommended) and Chat Completions (legacy) | xAI Console | xAI’s own quickstart uses the OpenAI SDK. Load credits before your first request. |
| DeepSeek | https://api.deepseek.com | Chat Completions; DeepSeek also lists a Responses API and an Anthropic-format endpoint | DeepSeek Platform | Thinking mode is switched with extra parameters. Prices halve outside peak hours. |
This page covers the companies whose prices Model Cost Check tracks.
Prices next to OpenAI’s
| Model | Input / output per 1M | 1,000 chat replies |
|---|---|---|
| Claude Haiku 5.5Anthropic | $0.10 / $0.50 | $0.45 |
| GPT-6 LunaOpenAI | $0.10 / $0.50 | $0.45 |
| DeepSeek FlashDeepSeek | $0.30 / $1.20 | $1.20 |
| Gemini 3.5 Flash-LiteGoogle · free tier | $0.30 / $2.50 | $1.85 |
| Gemini 3.8 FlashGoogle · free tier | $0.75 / $3.75 | $3.38 |
| DeepSeek V4 ProDeepSeek | $1.32 / $3.96 | $4.62 |
| Grok 4.7xAI | $2.00 / $6.00 | $7.00 |
| Claude Sonnet 5.5Anthropic | $2.00 / $10.00 | $9.00 |
| GPT-6.1 SolOpenAI | $2.00 / $10.00 | $9.00 |
| Gemini 4 ArgonGoogle | $2.00 / $10.00 | $9.00 |
| Claude Opus 5.5Anthropic | $4.00 / $20.00 | $18.00 |
| Claude Fable 5.1Anthropic | $10.00 / $50.00 | $45.00 |
| GPT-6 AstraOpenAI | $10.00 / $50.00 | $45.00 |
A chat reply here is 2,000 tokens in and 500 out. Prices from each company’s pricing page, checked October 13, 2026; DeepSeek’s are its peak-hour prices. Rank every model for other jobs, with batch prices, in the cheapest AI API tool.
What changes when you switch
- Three settings. Point the SDK at the new base URL, use that company’s API key, and pick one of its model names. Google sums it up as changing three lines of code.
- Some options are ignored. Anthropic’s layer quietly ignores fields it doesn’t support, such as
response_format,seedandlogprobs, ignores thestrictsetting on tools, needsnset to 1, and doesn’t take audio input. - Caching works differently. Prompt caching isn’t available through Anthropic’s OpenAI-compatible layer, so repeated input bills at the full input price; Anthropic’s own SDK supports it. Gemini’s cache is reached through
extra_body. - The same text is a different number of tokens. Anthropic says its Claude 4.7 and later models produce about 30% more tokens for the same text than its earlier tokenizer, so equal prices per token can still mean different bills. Try the token counter.
- Prompts may need work. A prompt tuned for OpenAI’s models may need reworking for another company’s, Anthropic notes.
- Limits and data rules follow the new company. Each applies its own rate limits, and on Google’s free tier your content can be used to improve Google’s products.
Questions
Which is cheaper, the Claude API or the OpenAI API?
At list prices, GPT-6 Luna and Claude Haiku 5.5 cost the same per token; so do GPT-6.1 Sol and Claude Sonnet 5.5, and GPT-6 Astra and Claude Fable 5.1. Claude Opus 5.5 has no OpenAI model at the same price. The bills can still differ: cached-input prices, long-prompt rules and token counts aren’t always the same, so compare with your own numbers in the cost calculator.
Is there a free alternative to the OpenAI API?
Google’s Gemini API has a free tier for Gemini 3.8 Flash and Gemini 3.5 Flash-Lite and several older models, with lower limits; Google uses free-tier content to improve its products.
Is xAI’s Grok API compatible with OpenAI?
Yes. xAI’s quickstart uses OpenAI’s SDK with the base URL https://api.x.ai/v1, and xAI recommends its Responses API over the older Chat Completions.
Can I use the OpenAI SDK with Claude?
Yes, to test and compare models. For production, Anthropic recommends its own API and SDKs, which add features such as prompt caching, citations and PDF support.
Do the alternatives support OpenAI’s Responses API?
xAI and DeepSeek list Responses API support. Anthropic’s and Google’s compatibility guides cover Chat Completions. See what the Responses API is.
Sources
- Anthropic: OpenAI SDK compatibility
- Google: OpenAI compatibility (page updated October 14, 2026)
- xAI: Quickstart and comparison with Chat Completions
- DeepSeek: Your first API call and models and pricing
- Read October 20, 2026. Prices: each company’s pricing page, checked October 13, 2026, listed in About and sources