Best Free LLM APIs for Chat

Chat models are the most common type of LLM, but they vary significantly in quality for conversation use:

• Latency / tokens per second — Real-time conversation needs fast responses. Groq's LPU hardware delivers the fastest inference (Llama 3.3 70B hits 100+ tok/s). NVIDIA NIM and OpenRouter are slower but offer more model variety.
• Context window — Long conversations or document Q&A need a large context window. Gemini 2.5 Flash (1M ctx) can hold an entire book in memory. Most chat models have 32K–128K, which handles typical back-and-forth conversations easily.
• Instruction following — A good chat model stays on-topic, follows system prompts, and avoids hallucinating. Llama 3.3 70B and Qwen3 are known for strong instruction adherence.
• Multilingual support — If you chat in non-English languages, check the model's training data. Qwen3 has strong Chinese/English bilingual performance. Gemini and Llama support 30+ languages.
• Multimodal input — Want to share images or audio in chat? Gemini 2.5 Flash accepts text, image, audio, and video. Most chat models are text-only.

Match the model to your chat use case:

• Casual conversation / chatbot? → Prioritize latency and personality. Llama 3.3 70B via Groq (fastest) or Gemini 2.5 Flash via Google AI Studio (most capable).
• Long-form Q&A / document chat? → Maximize context window. Gemini 2.5 Flash (1M) or Qwen3.5 122B (262K via NVIDIA NIM).
• Multilingual chat? → Qwen3.5 excels in Chinese-English. Gemini supports 30+ languages. Llama covers major European and Asian languages.
• Roleplay / creative conversation? → Look for models with strong creative writing. Llama 3.3 70B and Mistral models tend to have more varied output styles.
• Customer support bot? → Instruction following and safety are critical. Gemini and Qwen3 are well-aligned. Avoid unmoderated open models unless you add guardrails.