GPT-5.5 vs Grok 4.20
GPT-5.5 (2026) and Grok 4.20 (2026) are frontier-tier reasoning models from OpenAI and xAI. GPT-5.5 ships a 1.1M-token context window, while Grok 4.20 ships a 2M-token context window. On SWE-bench Verified, GPT-5.5 leads by 12 pts. On pricing, Grok 4.20 costs $1.25/1M input tokens versus $5/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Grok 4.20 is ~300% cheaper at $1.25/1M; pay for GPT-5.5 only for coding workflow support.
Specs
Pricing and availability
| Pricing attribute | GPT-5.5 | Grok 4.20 |
|---|---|---|
| Input price | $5/1M tokens | $1.25/1M tokens |
| Output price | $30/1M tokens | $2.5/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.5 | Grok 4.20 |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | No |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | No |
Benchmarks
| Benchmark | GPT-5.5 | Grok 4.20 |
|---|---|---|
| SWE-bench Verified | 88.7 | 76.7 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has GPT-5.5 at 88.7 and Grok 4.20 at 76.7, with GPT-5.5 ahead by 12 points. The largest visible gap is 12 points on SWE-bench Verified, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on vision: GPT-5.5, multimodal input: GPT-5.5, and code execution: GPT-5.5. Both models share reasoning mode, function calling, tool use, and structured outputs, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, GPT-5.5 lists $5/1M input and $30/1M output tokens, while Grok 4.20 lists $1.25/1M input and $2.5/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Grok 4.20 lower by about $10.88 per million blended tokens. Availability is 2 providers versus 2, so concentration risk also matters.
Choose GPT-5.5 when coding workflow support are central to the workload. Choose Grok 4.20 when long-context analysis, larger context windows, and lower input-token cost are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, GPT-5.5 or Grok 4.20?
Grok 4.20 supports 2M tokens, while GPT-5.5 supports 1.1M tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is cheaper, GPT-5.5 or Grok 4.20?
Grok 4.20 is cheaper on tracked token pricing. GPT-5.5 costs $5/1M input and $30/1M output tokens. Grok 4.20 costs $1.25/1M input and $2.5/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is GPT-5.5 or Grok 4.20 open source?
GPT-5.5 is listed under Proprietary. Grok 4.20 is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, GPT-5.5 or Grok 4.20?
GPT-5.5 has the clearer documented vision signal in this comparison. If vision is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, GPT-5.5 or Grok 4.20?
GPT-5.5 has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run GPT-5.5 and Grok 4.20?
GPT-5.5 is available on OpenAI API and OpenRouter. Grok 4.20 is available on xAI Console and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Continue comparing
Last reviewed: 2026-05-14. Data sourced from public model cards and provider documentation.