Claude API vs OpenAI API — Full Comparison 2025
Detailed comparison of Claude API and OpenAI API: pricing, models, context windows, coding performance, and which one to choose for your project.
Overview
Claude (by Anthropic) and GPT (by OpenAI) are the two leading LLM API platforms. Both offer powerful models, but they differ in pricing, capabilities, context handling, and developer experience. This guide helps you choose the right one — or use both.
Model Comparison
| Feature | Claude (Anthropic) | GPT (OpenAI) |
|---|---|---|
| Top model | Claude Opus 4.6 | GPT-4o / o1 |
| Mid-tier model | Claude Sonnet 4.6 | GPT-4o-mini |
| Fast/cheap model | Claude Haiku 4.5 | GPT-3.5 Turbo |
| Max context window | 200K tokens | 128K tokens |
| Vision (image input) | ✓ | ✓ |
| Tool/function calling | ✓ | ✓ |
| Streaming | ✓ | ✓ |
| Prompt caching | ✓ (90% cheaper) | ✓ (50% cheaper) |
Pricing Comparison
| Model Tier | Claude Input | Claude Output | OpenAI Input | OpenAI Output |
|---|---|---|---|---|
| Top tier | $15/1M (Opus) | $75/1M | $5/1M (GPT-4o) | $15/1M |
| Mid tier | $3/1M (Sonnet) | $15/1M | $0.15/1M (4o-mini) | $0.60/1M |
| Budget tier | $0.80/1M (Haiku) | $4/1M | $0.50/1M (3.5T) | $1.50/1M |
OpenAI's mid-tier is cheaper per token, but Claude's 200K context window means you can process larger documents in a single request — often reducing the total number of API calls needed.
When to Choose Claude
- Long documents — 200K context window handles entire codebases, legal docs, research papers
- Coding tasks — Claude Sonnet consistently ranks top on coding benchmarks (SWE-bench, HumanEval)
- Instruction following — Claude excels at following complex, multi-step instructions precisely
- Safety-critical apps — Anthropic's constitutional AI approach provides strong safety guardrails
- Prompt caching savings — 90% discount on cached tokens (vs 50% for OpenAI)
When to Choose OpenAI
- Ecosystem — larger ecosystem of tools, plugins, and third-party integrations
- Image generation — DALL-E integration for image creation (Claude is text/vision only)
- Budget mid-tier — GPT-4o-mini is very cheap for moderate-quality tasks
- Fine-tuning — OpenAI offers model fine-tuning; Claude does not
Using Both via ClaudeStore
ClaudeStore provides an OpenAI-compatible endpoint, so you can use the same client library for both Claude and GPT models. This makes it easy to:
- A/B test Claude vs GPT on your specific use case
- Use Claude for complex tasks and GPT for simple ones
- Switch models without changing your code
Many developers use Claude Sonnet for coding and GPT-4o-mini for summarization — getting the best of both worlds while minimizing costs.