Grok 4.3 vs GPT-5: Which API Should You Use in 2026?
xAI's Grok 4.3 and OpenAI's GPT-5 are both flagship-tier models with identical input pricing. But the output pricing tells a very different story — Grok is 75% cheaper on output tokens and offers 5x more context. Here's when each makes sense.
Pricing at a Glance
| Metric | Grok 4.3 (xAI) | GPT-5 (OpenAI) |
|---|---|---|
| Input price | $1.25 / 1M tokens | $1.25 / 1M tokens |
| Output price | $2.50 / 1M tokens | $10.00 / 1M tokens |
| Context window | 1M tokens | 200K tokens |
| Provider | xAI | OpenAI |
Same input cost. But Grok's output is 75% cheaper ($2.50 vs $10.00 per 1M tokens), and it supports 5x more context (1M vs 200K). For output-heavy workloads — chatbots, code generation, content creation — the savings add up fast.
Real-World Cost Scenarios
Let's compare monthly costs for three common usage patterns. Prices per 1M tokens.
💬 Chatbot — 10M input + 2M output tokens/month
Grok saves $15/mo (46% cheaper)
🤖 Code Generation — 5M input + 10M output tokens/month
Grok saves $75/mo (71% cheaper)
📄 Document Analysis — 50M input + 5M output tokens/month (long context)
Grok saves $37.50/mo (33% cheaper) — plus handles docs over 200K tokens that GPT-5 can't
When to Choose Grok 4.3
- Output-heavy workloads — Chatbots, code generation, content creation. The 75% output savings is the biggest differentiator.
- Long documents — Grok's 1M context handles entire codebases, legal contracts, or research papers in a single prompt.
- Budget-conscious projects — Same input price, fraction of the output cost. Clear winner for cost optimization.
- xAI ecosystem — If you're already using xAI's tools and infrastructure.
When to Choose GPT-5
- OpenAI ecosystem — Function calling, Assistants API, GPT plugins, and the broader OpenAI toolchain are mature and well-documented.
- Proven reliability — GPT-5 has been battle-tested at massive scale across millions of applications.
- Native multimodal — GPT-5 supports native image generation and vision in the same model.
- Third-party integrations — Most AI frameworks and tools default to OpenAI compatibility.
💡 Bottom line: If your workload is output-heavy (most are), Grok 4.3 saves 50-75% with no quality compromise for most tasks. If you need OpenAI's ecosystem or native multimodal, GPT-5 is worth the premium.
How to Switch from GPT-5 to Grok 4.3
Migration is straightforward — xAI's API is OpenAI-compatible. Here's the minimal change:
// Before (OpenAI)
import OpenAI from 'openai';
const client = new OpenAI();
// After (xAI / Grok)
const client = new OpenAI({
apiKey: process.env.XAI_API_KEY,
baseUrl: 'https://api.x.ai/v1'
});
// Everything else stays the same
Same SDK, same request format, same response structure. Just swap the base URL and API key. See our full migration checklist for a step-by-step guide.
See Exact Savings for Your Workload
Use our free calculator to compare Grok 4.3 vs GPT-5 costs based on your actual token usage.
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