Pick GPT-5.1 for adaptive reasoning that scales compute to task difficulty or general-purpose reasoning, coding and tool use. Pick Grok 4.3 for video understanding from native video input or generating pdf, pptx, and xlsx files directly.
GPT-5.1 (OpenAI) and Grok 4.3 (xAI) are two of the models people most often weigh against each other in 2026. GPT-5.1 is openAI's late-2025 GPT-5.1 at $1.25/$10 — a capable general model since surpassed by the GPT-5.2–5.6 line. Grok 4.3 is the current xAI flagship: 1M context, native video input, file generation, and live X data, ahead of the still-unreleased Grok 5. Their biggest split is context window, and the breakdown below shows exactly how that plays out for your workload.
Key differences
Context window: Grok 4.3 holds 2.5× more — 1M (~1,500 pages) vs 400K (~600 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
Recency: Grok 4.3 is the newer model by about 6 months (released April 30, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
GPT-5.1
Grok 4.3
Provider
OpenAI (US)
xAI (US)
Released
November 13, 2025
April 30, 2026
Context window
400K (~600 pages)
1M (~1,500 pages)
Price (in/out)
$1.25/$10 per 1M tokens
$1.25/$2.5 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, image, video, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Adaptive reasoning that scales compute to task difficulty: GPT-5.1 — GPT-5.1 lists adaptive reasoning that scales compute to task difficulty among its strengths; Grok 4.3 does not.
General-purpose reasoning, coding and tool use: GPT-5.1 — GPT-5.1 lists general-purpose reasoning, coding and tool use among its strengths; Grok 4.3 does not.
A large ~400K context for long documents and sessions: GPT-5.1 — Grok 4.3 is comparatively weak here — higher context pricing on requests above 200K tokens
Video understanding from native video input: Grok 4.3 — The current xAI flagship: 1M context, native video input, file generation, and live X data, ahead of the still-unreleased Grok 5 — and it carries the larger 1M context.
Generating PDF, PPTX, and XLSX files directly: Grok 4.3 — The current xAI flagship: 1M context, native video input, file generation, and live X data, ahead of the still-unreleased Grok 5 — and it is the newer of the two.
Real-time questions using live X data: Grok 4.3 — Grok 4.3 lists real-time questions using live X data among its strengths; GPT-5.1 does not.
Largest single-prompt input: Grok 4.3 — Its 1M window is about 2.5× larger than GPT-5.1's 400K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
Someone analysing very long documents or codebases: Grok 4.3 — Larger 1M window fits more in one prompt.
Anyone whose priority is adaptive reasoning that scales compute to task difficulty: GPT-5.1 — It is specifically built for that.
Anyone whose priority is video understanding from native video input: Grok 4.3 — That is its strongest area.
GPT-5.1: where it fits
OpenAI's late-2025 GPT-5.1 at $1.25/$10 — a capable general model since surpassed by the GPT-5.2–5.6 line. Released November 13, 2025 by OpenAI, it is built for adaptive reasoning that scales compute to task difficulty, general-purpose reasoning, coding and tool use, a large ~400K context for long documents and sessions, and text and image input.
Its trade-offs are real: superseded by GPT-5.2 through GPT-5.6 — kept for compatibility rather than being current, no reliably published SWE-Bench Verified figure, exact context window unconfirmed (400K vs 410K across trackers), and premium output price at $10/1M for a now-older model. At $1.25 in / $10 out per million tokens, it sits in the mid price band.
Grok 4.3: where it fits
The current xAI flagship: 1M context, native video input, file generation, and live X data, ahead of the still-unreleased Grok 5. Released April 30, 2026 by xAI, it is built for video understanding from native video input, generating PDF, PPTX, and XLSX files directly, real-time questions using live X data, and long-context, multi-agent reasoning.
Its trade-offs: higher context pricing on requests above 200K tokens, and less independent benchmark coverage than OpenAI, Anthropic, or Google. At $1.25 in / $2.5 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
GPT-5.1 and Grok 4.3 overlap enough that the right pick depends on your specific job. Grok 4.3 holds the larger context; and each leads in its own area — GPT-5.1 for adaptive reasoning that scales compute to task difficulty, Grok 4.3 for video understanding from native video input. Rather than crowning one, run the same hard task through both once and let the results decide.
Frequently asked questions
Is GPT-5.1 or Grok 4.3 better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, GPT-5.1 leans toward adaptive reasoning that scales compute to task difficulty while Grok 4.3 leans toward video understanding from native video input, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, GPT-5.1 or Grok 4.3?
They are priced almost identically, so cost will not decide between them.
Which has the bigger context window?
Grok 4.3 — 1M vs 400K, about 2.5× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both GPT-5.1 and Grok 4.3 together?
Yes — a multi-model platform like LumiChats gives you GPT-5.1, Grok 4.3 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, GPT-5.1 or Grok 4.3?
Grok 4.3 — released April 30, 2026, about 6 months after GPT-5.1.
GPT-5.1 vs Grok 4.3
OpenAI · US | xAI · US · Updated June 2026
Quick verdict
Pick GPT-5.1 for adaptive reasoning that scales compute to task difficulty or general-purpose reasoning, coding and tool use. Pick Grok 4.3 for video understanding from native video input or generating pdf, pptx, and xlsx files directly.
GPT-5.1 (OpenAI) and Grok 4.3 (xAI) are two of the models people most often weigh against each other in 2026. GPT-5.1 is openAI's late-2025 GPT-5.1 at $1.25/$10 — a capable general model since surpassed by the GPT-5.2–5.6 line. Grok 4.3 is the current xAI flagship: 1M context, native video input, file generation, and live X data, ahead of the still-unreleased Grok 5. Their biggest split is context window, and the breakdown below shows exactly how that plays out for your workload.
Key differences at a glance
▸Context window: Grok 4.3 holds 2.5× more — 1M (~1,500 pages) vs 400K (~600 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
▸Recency: Grok 4.3 is the newer model by about 6 months (released April 30, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
GPT-5.1
Grok 4.3
Provider
OpenAI (US)
xAI (US)
Released
November 13, 2025
April 30, 2026
Context window
400K (~600 pages)
1M (~1,500 pages)
Price (in/out)
$1.25/$10 per 1M tokens
$1.25/$2.5 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, image, video, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Adaptive reasoning that scales compute to task difficulty
GPT-5.1
GPT-5.1 lists adaptive reasoning that scales compute to task difficulty among its strengths; Grok 4.3 does not.
General-purpose reasoning, coding and tool use
GPT-5.1
GPT-5.1 lists general-purpose reasoning, coding and tool use among its strengths; Grok 4.3 does not.
A large ~400K context for long documents and sessions
GPT-5.1
Grok 4.3 is comparatively weak here — higher context pricing on requests above 200K tokens
Video understanding from native video input
Grok 4.3
The current xAI flagship: 1M context, native video input, file generation, and live X data, ahead of the still-unreleased Grok 5 — and it carries the larger 1M context.
Generating PDF, PPTX, and XLSX files directly
Grok 4.3
The current xAI flagship: 1M context, native video input, file generation, and live X data, ahead of the still-unreleased Grok 5 — and it is the newer of the two.
Real-time questions using live X data
Grok 4.3
Grok 4.3 lists real-time questions using live X data among its strengths; GPT-5.1 does not.
Largest single-prompt input
Grok 4.3
Its 1M window is about 2.5× larger than GPT-5.1's 400K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
Someone analysing very long documents or codebases
→ Grok 4.3
Larger 1M window fits more in one prompt.
Anyone whose priority is adaptive reasoning that scales compute to task difficulty
→ GPT-5.1
It is specifically built for that.
Anyone whose priority is video understanding from native video input
→ Grok 4.3
That is its strongest area.
GPT-5.1: where it fits
OpenAI's late-2025 GPT-5.1 at $1.25/$10 — a capable general model since surpassed by the GPT-5.2–5.6 line. Released November 13, 2025 by OpenAI, it is built for adaptive reasoning that scales compute to task difficulty, general-purpose reasoning, coding and tool use, a large ~400K context for long documents and sessions, and text and image input.
Its trade-offs are real: superseded by GPT-5.2 through GPT-5.6 — kept for compatibility rather than being current, no reliably published SWE-Bench Verified figure, exact context window unconfirmed (400K vs 410K across trackers), and premium output price at $10/1M for a now-older model. At $1.25 in / $10 out per million tokens, it sits in the mid price band.
Grok 4.3: where it fits
The current xAI flagship: 1M context, native video input, file generation, and live X data, ahead of the still-unreleased Grok 5. Released April 30, 2026 by xAI, it is built for video understanding from native video input, generating PDF, PPTX, and XLSX files directly, real-time questions using live X data, and long-context, multi-agent reasoning.
Its trade-offs: higher context pricing on requests above 200K tokens, and less independent benchmark coverage than OpenAI, Anthropic, or Google. At $1.25 in / $2.5 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
GPT-5.1 and Grok 4.3 overlap enough that the right pick depends on your specific job. Grok 4.3 holds the larger context; and each leads in its own area — GPT-5.1 for adaptive reasoning that scales compute to task difficulty, Grok 4.3 for video understanding from native video input. Rather than crowning one, run the same hard task through both once and let the results decide.
Want both GPT-5.1 and Grok 4.3 without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, GPT-5.1 leans toward adaptive reasoning that scales compute to task difficulty while Grok 4.3 leans toward video understanding from native video input, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, GPT-5.1 or Grok 4.3?
They are priced almost identically, so cost will not decide between them.
Which has the bigger context window?
Grok 4.3 — 1M vs 400K, about 2.5× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both GPT-5.1 and Grok 4.3 together?
Yes — a multi-model platform like LumiChats gives you GPT-5.1, Grok 4.3 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, GPT-5.1 or Grok 4.3?
Grok 4.3 — released April 30, 2026, about 6 months after GPT-5.1.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.