GPT-5.1-Codex vs Grok 4.20
Grok 4.20 leads GPT-5.1-Codex on coding, 33.3 to 15.3 on the Vibe Coding Index, and Grok 4.20 costs 4.0x less per output token ($2.50 vs $10.00 per million). Updated October 21, 2026; 18 benchmarks have a result for both.
GPT-5.1-Codex or Grok 4.20: which to pick
Pick Grok 4.20 for coding: it scores 33.3 on the Vibe Coding Index against 15.3 for GPT-5.1-Codex.
Pick GPT-5.1-Codex for work measured by LiveCodeBench (Vals AI) or Vibe Code Bench (Vals AI), where it leads.
- Shared results
- 18
- GPT-5.1-Codex only
- 8
- Grok 4.20 only
- 37
- Like-for-like categories
- 6 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
Grok 4.20
Grok 4.20 scores 33.3 against 15.3.
2 benchmarks behind each score
Intelligence
AA Intelligence Index
Grok 4.20
Grok 4.20 leads, 25.7 against 23.7.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only Grok 4.20 has a GPQA Diamond result, 88.6%.
Directional only
Math
AIME
No call
Only Grok 4.20 has a AIME result, 96.5%.
Directional only
Knowledge
MMLU Pro
No call
Only Grok 4.20 has a MMLU Pro result, 86.3%.
Directional only
Web design
Design Arena: websites
Grok 4.20
Grok 4.20 leads, 1229 against 1162.
Same board, both measured
Long documents
Listed context window
Grok 4.20
Grok 4.20 takes 2M tokens against 400K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Grok 4.20
GPT-5.1-Codex $0.0063, Grok 4.20 $0.0025 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
Grok 4.20
GPT-5.1-Codex $0.892, Grok 4.20 $0.72.
Published attempt cost and pass rate
At a glance
- Coding index
- GPT-5.1-Codex 15.3 from 2 benchmarks, Grok 4.20 33.3 from 2 benchmarks.
- Widest category
- Agentic work, 10.6 points apart on average over 4 shared benchmarks.
- Widest single gap
- Design Arena: agents building web apps: GPT-5.1-Codex 1018 against Grok 4.20 1144, 15.8 points apart on a 0 to 100 scale.
- Output price
- GPT-5.1-Codex $10.00 against Grok 4.20 $2.50 per million output tokens, 4.0x apart.
- Context window
- GPT-5.1-Codex takes 400K tokens, Grok 4.20 2M.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | GPT-5.1-Codex | Bars | Grok 4.20 | Ties |
|---|---|---|---|---|
| Coding | 3 | 1 | ||
| Intelligence | 0 | 1 | ||
| Agentic work | 2 | 2 | ||
| Reasoning | 0 | 2 | ||
| Web design | 1 | 4 | ||
| General | 1 | 1 | ||
| All shared boards | 7 | 11 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index31
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Leader |
|---|---|---|---|
| SWE-bench Verified | 66.0% | Not measured | Only GPT-5.1-Codex measured |
| LMArena WebDev | 1337 | Not measured | Only GPT-5.1-Codex measured |
| LiveCodeBench (Vals AI) | 85.5% | 84.3% | GPT-5.1-Codex |
| SWE-bench Verified (Vals AI) | Not measured | 72.2% | Only Grok 4.20 measured |
| Vibe Code Bench (Vals AI) | 13.1% | 4.1% | GPT-5.1-Codex |
| Code migration (Vals AI) | Not measured | 0.3% | Only Grok 4.20 measured |
| Terminal-Bench 2.1 (Vals AI) | Not measured | 44.2% | Only Grok 4.20 measured |
| LiveCodeBench (Artificial Analysis run) | 84.9% | Not measured | Only GPT-5.1-Codex measured |
| Terminal-Bench Hard (Artificial Analysis run) | 34.8% | 37.9% | Grok 4.20 |
| Terminal-Bench | 57.8% | 57.3% | GPT-5.1-Codex |
| WeirdML | Not measured | 52.3% | Only Grok 4.20 measured |
| ALE-Bench | 1244.9 | Not measured | Only GPT-5.1-Codex measured |
| LMArena WebDev: HTML | 1346 | Not measured | Only GPT-5.1-Codex measured |
| Neither model has a result on the other 26 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Leader |
|---|---|---|---|
| AA Intelligence Index | 23.7 | 25.7 | Grok 4.20 |
| Epoch Capabilities Index | Not measured | 152.1 | Only Grok 4.20 measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index22
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1018 | 1144 | Grok 4.20 |
| Design Arena: agents building full-stack apps | 1086 | 1054 | GPT-5.1-Codex |
| Design Arena: agents building mobile apps | 1191 | 1090 | GPT-5.1-Codex |
| Design Arena: agents building Android apps | Not measured | 1052 | Only Grok 4.20 measured |
| Design Arena: agents building Godot games | Not measured | 1089 | Only Grok 4.20 measured |
| Design Arena: HTML slides | Not measured | 1180 | Only Grok 4.20 measured |
| Finance Agent (Vals AI) | Not measured | 28.5% | Only Grok 4.20 measured |
| Tax Agent Bench (Vals AI) | Not measured | 7.0% | Only Grok 4.20 measured |
| Legal Research Bench (Vals AI) | Not measured | 13.9% | Only Grok 4.20 measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 11.7% | Only Grok 4.20 measured |
| τ²-Bench Telecom | 83.0% | 93.0% | Grok 4.20 |
| Vending-Bench 2 | Not measured | $4,663 | Only Grok 4.20 measured |
| Neither model has a result on the other 29 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Leader |
|---|---|---|---|
| GPQA Diamond | Not measured | 88.6% | Only Grok 4.20 measured |
| MMMU Pro (Vals AI) | Not measured | 83.5% | Only Grok 4.20 measured |
| GPQA Diamond (Artificial Analysis run) | 86.0% | 91.1% | Grok 4.20 |
| Humanity's Last Exam (Artificial Analysis run) | 25.7% | 34.5% | Grok 4.20 |
| ARC-AGI | Not measured | 89.5% | Only Grok 4.20 measured |
| ARC-AGI-2 | Not measured | 65.1% | Only Grok 4.20 measured |
| Kagi LLM Benchmark | Not measured | 75.0% | Only Grok 4.20 measured |
| Neither model has a result on the other 15 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index3 boards, none shared
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Leader |
|---|---|---|---|
| AIME | Not measured | 96.5% | Only Grok 4.20 measured |
| AA Math Index | 95.7 | Not measured | Only GPT-5.1-Codex measured |
| AIME 2025 (Artificial Analysis run) | 95.7% | Not measured | Only GPT-5.1-Codex measured |
| Neither model has a result on the other 10 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Leader |
|---|---|---|---|
| MMLU Pro | Not measured | 86.3% | Only Grok 4.20 measured |
| LegalBench (Vals AI) | Not measured | 77.7% | Only Grok 4.20 measured |
| CaseLaw (Vals AI) | Not measured | 54.4% | Only Grok 4.20 measured |
| CorpFin (Vals AI) | Not measured | 63.7% | Only Grok 4.20 measured |
| TaxEval (Vals AI) | Not measured | 74.1% | Only Grok 4.20 measured |
| MortgageTax (Vals AI) | Not measured | 45.4% | Only Grok 4.20 measured |
| MedQA (Vals AI) | Not measured | 94.5% | Only Grok 4.20 measured |
| MedCode (Vals AI) | Not measured | 32.2% | Only Grok 4.20 measured |
| MMLU Pro (Artificial Analysis run) | 86.0% | Not measured | Only GPT-5.1-Codex measured |
| Neither model has a result on the other 9 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index14
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Leader |
|---|---|---|---|
| Design Arena: websites | 1162 | 1229 | Grok 4.20 |
| Design Arena: UI components | 1237 | 1199 | GPT-5.1-Codex |
| Design Arena: game dev | 1138 | 1192 | Grok 4.20 |
| Design Arena: data viz | 1213 | 1217 | Grok 4.20 |
| Design Arena: 3D | Not measured | 1193 | Only Grok 4.20 measured |
| Design Arena: all code categories | 1152 | 1221 | Grok 4.20 |
| Design Arena: SVG | Not measured | 1164 | Only Grok 4.20 measured |
| Design Arena: ASCII art | Not measured | 1174 | Only Grok 4.20 measured |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index11
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Leader |
|---|---|---|---|
| SAGE (Vals AI) | Not measured | 38.2% | Only Grok 4.20 measured |
| MedScribe (Vals AI) | Not measured | 63.4% | Only Grok 4.20 measured |
| Vals Multimodal Index | Not measured | 39.1% | Only Grok 4.20 measured |
| IFBench | 70.0% | 81.2% | Grok 4.20 |
| Long context reasoning (AA-LCR) | 69.3% | 69.0% | GPT-5.1-Codex |
| DTBench | Not measured | 90.1% | Only Grok 4.20 measured |
| LMCA | Not measured | 38.7% | Only Grok 4.20 measured |
| CL-bench | Not measured | 22.2% | Only Grok 4.20 measured |
| CL-bench Life | Not measured | 11.9% | Only Grok 4.20 measured |
| Neither model has a result on the other 37 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
Grok 4.20 costs less
Repository review
50K input + 3K output tokens
Grok 4.20 costs less
Agent loop
200K input + 10K output tokens
Grok 4.20 costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | OpenAI GPT-5.1-Codex | SpaceXAI Grok 4.20 |
|---|---|---|
| Maker | OpenAI | xAI |
| Weights | No public weights listed | No public weights listed |
| Released | November 13, 2025 | March 31, 2026 |
| Context window | 400K | 2M |
| Input $/Mtok | $1.25 | $1.25 |
| Output $/Mtok | $10.00 | $2.50 |
| Coding index | 15.3 | 33.3 |
| Independent measurements behind it | 2 | 2 |
| Cost per solved task | $0.892 | $0.72 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is GPT-5.1-Codex better than Grok 4.20 for coding?
Pick Grok 4.20 for coding: it scores 33.3 on the Vibe Coding Index against 15.3 for GPT-5.1-Codex. Pick GPT-5.1-Codex for work measured by LiveCodeBench (Vals AI) or Vibe Code Bench (Vals AI), where it leads.
Which is cheaper, GPT-5.1-Codex or Grok 4.20?
GPT-5.1-Codex costs $1.25 per million input tokens and $10.00 per million output tokens; Grok 4.20 costs $1.25 and $2.50. Per solved SWE-bench Verified task, GPT-5.1-Codex costs $0.892 and Grok 4.20 $0.72.
Which has the bigger context window, GPT-5.1-Codex or Grok 4.20?
Grok 4.20, with 2M tokens against 400K.
How many benchmarks is the GPT-5.1-Codex vs Grok 4.20 comparison based on?
18 benchmarks have a result for both models as of October 21, 2026. GPT-5.1-Codex's coding index rests on 2 independent benchmarks and Grok 4.20's on 2. Where only one model has a result, the page says so instead of naming a winner.