Claude API vs OpenAI API vs Gemini API: A Developer's Comparison

Choosing the right LLM API shapes everything downstream: your costs, latency, context limits, and the types of tasks your application can handle. In 2025, the three heavyweights are Anthropic's Claude API , OpenAI's API , and Google's Gemini API . Here's what you need to know before you commit. At a Glance Claude API OpenAI API Gemini API Top model Claude Opus 4 GPT-4o Gemini 1.5 Pro Context window 200K tokens 128K tokens 1M tokens Input price (approx) $15/M tokens $5/M tokens $3.50/M tokens Function calling Yes Yes Yes Streaming Yes Yes Yes Vision Yes Yes Yes Free tier No No Yes (generous) SDK languages Python, TS, Java Python, TS, .NET, Go Python, TS, Go, Java Prices as of early 2025. Check official pages for current rates. Claude API (Anthropic) Claude's API is built around a family of models: Haiku (fast/cheap), Sonnet (balanced), and Opus (most capable). The standout spec is the 200K token context window — about 150,000 words — which makes it exceptional for tasks like summarizing