GPT-5.1 Instant vs Grok 4 Fast: Specs & Benchmark Comparison
| Characteristic | GPT-5.1 Instant | Grok 4 Fast |
|---|---|---|
| Company | OpenAI | xAI |
| Release Date | November 11, 2025 | August 27, 2025 |
| Parameters | — | — |
| Multimodal | Yes | Yes |
| Context (input) | 256K | 2.0M |
| Context (output) | 32K | 30K |
| Input Price / 1M | $0.30 | $0.20 |
| Output Price / 1M | $1.20 | $0.50 |
| Average Score | 0.9 | 0.8 |
| Benchmarks | ||
| GPQA | 0.9 | 0.9 |
| AIME 2025 | 0.9 | 0.9 |
Visual Benchmark Comparison
GPT-5.1 Instant
Grok 4 Fast
GPQA0.9 vs 0.9
0.9
0.9
AIME 20250.9 vs 0.9
0.9
0.9
Verdict
Grok 4 Fast leads in 2 out of 4 comparison categories.
Overall Performance
Both models show comparable average scores: GPT-5.1 Instant — 0.9, Grok 4 Fast — 0.8.
API Cost
Grok 4 Fast is 2.1x cheaper: input $0.20/1M vs $0.30/1M tokens.
Context Window
Grok 4 Fast supports a larger context: 2M vs 256K tokens.
Recency
GPT-5.1 Instant is newer: released 11/11/2025 vs 8/27/2025.
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Frequently Asked Questions
Which is better for coding — GPT-5.1 Instant or Grok 4 Fast?
Direct comparison on the SWE-Bench benchmark is not available. We recommend reviewing other metrics on the comparison page.
Which model is cheaper — GPT-5.1 Instant or Grok 4 Fast?
Grok 4 Fast is cheaper for input: $0.20 per 1M tokens vs $0.30.
Which has a larger context window — GPT-5.1 Instant or Grok 4 Fast?
Grok 4 Fast supports a larger context: 2,000,000 tokens vs 256,000.
The GPT-5.1 Instant and Grok 4 Fast comparison is updated for 2026. Data includes benchmark results, API pricing, context window size and other specifications. For more detailed information, visit the GPT-5.1 Instant or Grok 4 Fast page. See also the complete list of AI model comparisons.