The 10 Best Free LLM APIs in 2025 (With Rate Limits & Model Quality Compared)
A ranked comparison of every major free LLM API option in 2025 — including rate limits, model quality, credit card requirements, and OpenAI compatibility.
Why Free LLM API Access Matters
The AI model landscape in 2025 is extraordinary. The gap between the best open-weight models and the best proprietary ones has narrowed dramatically. But API access still costs money — or does it? There are more free LLM API options available today than most developers realize. This guide ranks all ten major options based on what actually matters: models available, rate limits, credit card requirements, and whether the API is OpenAI-compatible (so your code works across all of them).
1. FreeLLMKeys — Best for Model Variety
Models: 90+ including GPT-4o, Claude Opus, Gemini, DeepSeek, Grok, Mistral
Rate Limits: 3–20 RPM depending on model
Credit Card Required: No
OpenAI-Compatible: Yes
Best For: Prototyping across multiple models, students, indie developers
FreeLLMKeys offers the broadest model selection of any free option, updated multiple times daily. The tradeoff is that keys expire in 24–48 hours and you need to grab a fresh one periodically. For development and testing, this is a non-issue.
2. Groq — Best for Raw Speed
Models: Llama 3.3, Mixtral, Gemma
Rate Limits: ~30 RPM on free tier
Credit Card Required: No (signup required)
OpenAI-Compatible: Yes (base URL: https://api.groq.com/openai/v1)
Best For: Any application where latency matters — chatbots, real-time tools
Groq runs on custom LPU hardware and delivers inference speeds of 800+ tokens per second — orders of magnitude faster than GPU-based APIs. The free tier is genuinely usable, though model selection is limited to open-weight models.
3. Google AI Studio — Best for Gemini Access
Models: Gemini 2.5 Flash, Gemini 2.0 Pro
Rate Limits: 15 RPM on free tier
Credit Card Required: No (Google account required)
OpenAI-Compatible: Partially (via compatibility endpoint)
Best For: Long-context tasks, multimodal (image + text), Google ecosystem
Google AI Studio is the most generous official free tier from a major provider. Gemini 2.5 Flash is fast and capable, and the 1M token context window is unmatched. Note: Google's data usage policy differs outside the EU — prompts may be used to improve models.
4. OpenRouter — Best for Aggregation
Models: 100+ (Claude, GPT-4, Gemini, Llama, and more)
Rate Limits: Varies by model and account credits
Credit Card Required: No for free models
OpenAI-Compatible: Yes
Best For: Developers who want one API for everything
OpenRouter aggregates many providers into one API. Several models are permanently free (Llama, Gemma, etc.) and they occasionally offer free credits for newer models. A great backup option when other free keys are exhausted.
5. Together AI — Good Free Tier for Open Models
Models: Llama 4, Qwen, Mistral, DeepSeek
Rate Limits: Generous on free trial credits
Credit Card Required: No (limited free credits on signup)
OpenAI-Compatible: Yes
Best For: Open-weight model experimentation
6. Mistral AI — Good for European Data Compliance
Models: Mistral 7B, Mistral Medium, Codestral
Rate Limits: Limited free tier
Credit Card Required: No for trial period
OpenAI-Compatible: Yes
Best For: EU-based projects needing GDPR-compliant inference
7. Hugging Face Inference API — Best for Open Models
Models: Any public model on Hugging Face Hub
Rate Limits: Low on free tier
Credit Card Required: No
OpenAI-Compatible: Partially
Best For: Accessing niche or fine-tuned open-source models
8. Cloudflare AI Workers — Serverless Free Tier
Models: Llama, Mistral, Phi, Stable Diffusion
Rate Limits: 10K neurons/day on free tier
Credit Card Required: No
OpenAI-Compatible: No (custom API format)
Best For: Edge AI with Cloudflare Workers integration
9. Cohere — Good for Embeddings
Models: Command R+, Embed
Rate Limits: Trial API key with limited calls
Credit Card Required: No
OpenAI-Compatible: No
Best For: RAG applications needing embeddings + generation in one API
10. Replicate — Good for Image Models
Models: Llama, Stable Diffusion, SDXL, Flux
Rate Limits: Small free credit on signup
Credit Card Required: No for initial credits
OpenAI-Compatible: No
Best For: Image generation, multimodal experiments
Why OpenAI-Compatible APIs Matter
If an API is OpenAI-compatible, your code works across all of them with a single line change — just swap the base_url. This portability is worth more than any individual feature. FreeLLMKeys, Groq, OpenRouter, Together AI, and Mistral are all fully compatible. Build on any of them and you can switch to any other in seconds.
For most developers starting out, the recommendation is: start with FreeLLMKeys for maximum model variety, add Groq if speed is critical, and keep Google AI Studio as a backup for Gemini-specific tasks.