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Best LLM API for adding AI to your app

Pick a model API for chat, agents or AI features in your product.

3 picks, ordered by fit for this job. The score is each tool's overall editorial score out of 10. Adoption inside that score is an estimate.

#1 by fit
OpenRouter
LLM APIs & Model Routing
7/10Overall scorecap 3 · value 2 · ease 1 · adopt* 1
One key for hundreds of models with fallbacks; free models to prototype.
Best for
Trying and switching models easily
Skip if
You need direct provider contracts
FreemiumFree models · pay-as-you-go
Free tier with 25+ free models; pay-as-you-go standard tier; Enterprise via sales. Platform fees listed on pricing page. Price source · checked Oct 20, 2026
Note: Exact platform fee % not captured
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#2 by fit
Gemini API (Google AI Studio)
LLM APIs & Model Routing
7/10Overall scorecap 3 · value 2 · ease 1 · adopt* 1
Free tier in AI Studio and long-context multimodal models.
Best for
Prototyping on $0
Skip if
Free-tier data use is a concern
FreemiumFree tier · pay per token
Free tier with limited models/rate limits (content may be used to improve products). Paid per-1M tokens; e.g. flagship Gemini 4 Argon $2 in/$10 out through Nov 30, 2026, then $4/$20. Price source · checked Oct 20, 2026
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#3 by fit
OpenAI API
LLM APIs & Model Routing
7/10Overall scorecap 4 · value 1 · ease 0 · adopt* 2
Frontier GPT models plus a very cheap small model for volume.
Best for
Production AI features at scale
Skip if
You need a free tier
PaidPay per token (e.g. GPT-6 Luna $0.10 in / $0.50 out per 1M)
Per-1M-token pricing, e.g. flagship $10 in/$50 out, GPT-6.1 Sol $2 in/$10 out, GPT-6 Luna $0.10 in/$0.50 out (standard processing, <272K context). Price source · checked Oct 20, 2026
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OpenRouter

Gemini API (Google AI Studio)

OpenAI API