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GPT-4o vs GPT-5.1-Codex

Updated October 21, 2026. 16 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace GPT-4o Replace GPT-5.1-Codex
GPT-4oOpenAI
Coding
38.8
Overall
No data
Output $/M
$10.00
0
GPT-5.1-CodexOpenAI
Coding
50.5
Overall
23.7
Output $/M
$10.00
16
vs boards won of 16 shared

Decision reading

Pick GPT-5.1-Codex for coding: it scores 50.5 on the Vibe Coding Index against 38.8 for GPT-4o.

GPT-4o is neither cheaper nor larger in context, and leads no benchmark both models were measured on.

Model AGPT-4oOpenAI38.8/1001 independent benchmarkNo cost per solved taskModel BGPT-5.1-CodexOpenAI50.5/1002 independent benchmarks$0.892 per solved task
Shared results
16
GPT-4o only
10
GPT-5.1-Codex only
10
Like-for-like categories
7 of 9

Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.

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.

At a glance

Coding index
GPT-4o 38.8 from 1 benchmark, GPT-5.1-Codex 50.5 from 2 benchmarks.
Widest category
Math, 89.7 points apart on average over 2 shared benchmarks.
Widest single gap
AA Math Index: GPT-4o 6.0 against GPT-5.1-Codex 95.7, 89.7 points apart on a 0 to 100 scale.
Output price
Both cost $10.00 per million output tokens.
Context window
GPT-4o takes 128K tokens, GPT-5.1-Codex 400K.

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.

Boards won, where both have a result
CategoryGPT-4oBarsGPT-5.1-CodexTies
Coding03
Agentic work01
Reasoning02
Math02
Knowledge01
Web design05
General02
All shared boards016
CodingLike-for-likeFour of these boards feed the Vibe Coding Index03
Coding benchmarks for GPT-4o and GPT-5.1-Codex
BenchmarkGPT-4oGPT-5.1-CodexLeader
SWE-bench Verified38.8%66.0%GPT-5.1-Codex
SWE-bench Lite38.0%Not measuredOnly GPT-4o measured
SWE-bench (full test set)18.8%Not measuredOnly GPT-4o measured
SWE-bench Multimodal30.4%Not measuredOnly GPT-4o measured
LMArena WebDevNot measured1337Only GPT-5.1-Codex measured
LiveCodeBench (Vals AI)Not measured85.5%Only GPT-5.1-Codex measured
Vibe Code Bench (Vals AI)Not measured13.1%Only GPT-5.1-Codex measured
LiveCodeBench (Artificial Analysis run)30.9%84.9%GPT-5.1-Codex
Terminal-Bench Hard (Artificial Analysis run)8.3%34.8%GPT-5.1-Codex
Terminal-BenchNot measured57.8%Only GPT-5.1-Codex measured
ALE-BenchNot measured1244.9Only GPT-5.1-Codex measured
LMArena WebDev: HTMLNot measured1346Only GPT-5.1-Codex measured
Neither model has a result on the other 26 boards here
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
Intelligence benchmarks for GPT-4o and GPT-5.1-Codex
BenchmarkGPT-4oGPT-5.1-CodexLeader
AA Intelligence IndexNot measured23.7Only GPT-5.1-Codex measured
Neither model has a result on the other 1 board here
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
Agentic work benchmarks for GPT-4o and GPT-5.1-Codex
BenchmarkGPT-4oGPT-5.1-CodexLeader
Design Arena: agents building web appsNot measured1018Only GPT-5.1-Codex measured
Design Arena: agents building full-stack appsNot measured1086Only GPT-5.1-Codex measured
Design Arena: agents building mobile appsNot measured1191Only GPT-5.1-Codex measured
τ²-Bench Telecom25.1%83.0%GPT-5.1-Codex
GDPval9.9%Not measuredOnly GPT-4o measured
Neither model has a result on the other 34 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index02
Reasoning benchmarks for GPT-4o and GPT-5.1-Codex
BenchmarkGPT-4oGPT-5.1-CodexLeader
GPQA Diamond (Artificial Analysis run)54.3%86.0%GPT-5.1-Codex
Humanity's Last Exam (Artificial Analysis run)2.4%25.7%GPT-5.1-Codex
ARC-AGI4.5%Not measuredOnly GPT-4o measured
ARC-AGI-20.0%Not measuredOnly GPT-4o measured
Neither model has a result on the other 17 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index02
Math benchmarks for GPT-4o and GPT-5.1-Codex
BenchmarkGPT-4oGPT-5.1-CodexLeader
AA Math Index6.095.7GPT-5.1-Codex
AIME 2025 (Artificial Analysis run)6.0%95.7%GPT-5.1-Codex
Neither model has a result on the other 11 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index01
Knowledge benchmarks for GPT-4o and GPT-5.1-Codex
BenchmarkGPT-4oGPT-5.1-CodexLeader
MMLU Pro (Artificial Analysis run)74.8%86.0%GPT-5.1-Codex
MMLU88.1%Not measuredOnly GPT-4o measured
Neither model has a result on the other 15 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index05
Web design benchmarks for GPT-4o and GPT-5.1-Codex
BenchmarkGPT-4oGPT-5.1-CodexLeader
Design Arena: websites8311162GPT-5.1-Codex
Design Arena: UI components8851237GPT-5.1-Codex
Design Arena: game dev9061138GPT-5.1-Codex
Design Arena: data viz8581213GPT-5.1-Codex
Design Arena: 3D869Not measuredOnly GPT-4o measured
Design Arena: all code categories8611153GPT-5.1-Codex
Neither model has a result on the other 3 boards here
GeneralLike-for-likePublic boards, shown as published, kept out of the index02
General benchmarks for GPT-4o and GPT-5.1-Codex
BenchmarkGPT-4oGPT-5.1-CodexLeader
IFBench34.3%70.0%GPT-5.1-Codex
Long context reasoning (AA-LCR)49.3%69.3%GPT-5.1-Codex
DTBench64.5%Not measuredOnly GPT-4o measured
LMCA16.6%Not measuredOnly GPT-4o measured
Neither model has a result on the other 42 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for GPT-4o and GPT-5.1-Codex
BenchmarkGPT-4oGPT-5.1-CodexLeader
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

GPT-4o$0.0075Fits in one request
GPT-5.1-Codex$0.0063Fits in one request

GPT-5.1-Codex costs less

Repository review

50K input + 3K output tokens

GPT-4o$0.155Fits in one request
GPT-5.1-Codex$0.092Fits in one request

GPT-5.1-Codex costs less

Agent loop

200K input + 10K output tokens

GPT-4o$0.600Exceeds the context window
GPT-5.1-Codex$0.350Fits in one request

GPT-5.1-Codex 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.

Specifications of GPT-4o and GPT-5.1-Codex
SpecificationOpenAI GPT-4oOpenAI GPT-5.1-Codex
MakerOpenAIOpenAI
WeightsNo public weights listedNo public weights listed
ReleasedMay 13, 2024November 13, 2025
Context window128K400K
Input $/Mtok$2.50$1.25
Output $/Mtok$10.00$10.00
Coding index38.850.5
Independent measurements behind it12
Cost per solved taskNot computable$0.892
SourceOpenRouter listingOpenRouter listing

Questions

Is GPT-4o better than GPT-5.1-Codex for coding?

Pick GPT-5.1-Codex for coding: it scores 50.5 on the Vibe Coding Index against 38.8 for GPT-4o. GPT-4o is neither cheaper nor larger in context, and leads no benchmark both models were measured on.

Which is cheaper, GPT-4o or GPT-5.1-Codex?

GPT-4o costs $2.50 per million input tokens and $10.00 per million output tokens; GPT-5.1-Codex costs $1.25 and $10.00. Cost per solved task is known for GPT-5.1-Codex only.

Which has the bigger context window, GPT-4o or GPT-5.1-Codex?

GPT-5.1-Codex, with 400K tokens against 128K.

How many benchmarks is the GPT-4o vs GPT-5.1-Codex comparison based on?

16 benchmarks have a result for both models as of October 21, 2026. GPT-4o's coding index rests on 1 independent benchmark and GPT-5.1-Codex's on 2. Where only one model has a result, the page says so instead of naming a winner.

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