Gemini 3.1 Pro Preview Custom Tools vs GPT-5.3-Codex
Gemini 3.1 Pro Preview Custom Tools and GPT-5.3-Codex cost about the same per output token ($12.00 vs $14.00 per million). Updated October 21, 2026; 1 benchmarks have a result for both.
Gemini 3.1 Pro Preview Custom Tools or GPT-5.3-Codex: which to pick
Only GPT-5.3-Codex has a coding score, 60.0 on the Vibe Coding Index; Gemini 3.1 Pro Preview Custom Tools has none, so the two cannot be ranked on coding.
Pick Gemini 3.1 Pro Preview Custom Tools for output tokens 1.2x cheaper ($12.00 vs $14.00 per million) and a larger context window (1.05M against 400K tokens).
- Shared results
- 1
- Gemini 3.1 Pro Preview Custom Tools only
- 0
- GPT-5.3-Codex only
- 33
- Like-for-like categories
- 1 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
No call
Only GPT-5.3-Codex has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
No call
Only GPT-5.3-Codex has a AA Intelligence Index result, 32.5.
Directional only
Web design
Design Arena: websites
No call
Only GPT-5.3-Codex has a Design Arena: websites result, 1163.
Directional only
Long documents
Listed context window
Gemini 3.1 Pro Preview Custom Tools
Gemini 3.1 Pro Preview Custom Tools takes 1.05M tokens against 400K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Gemini 3.1 Pro Preview Custom Tools
Gemini 3.1 Pro Preview Custom Tools $0.0080, GPT-5.3-Codex $0.0088 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only GPT-5.3-Codex has the number, $0.59.
Directional only
At a glance
- Coding index
- Gemini 3.1 Pro Preview Custom Tools not benchmarked, GPT-5.3-Codex 60.0 from 3 benchmarks.
- Widest category
- Agentic work, 13.5 points apart on average over 1 shared benchmark.
- Widest single gap
- Vending-Bench 2: Gemini 3.1 Pro Preview Custom Tools $3,774 against GPT-5.3-Codex $5,940, 13.5 points apart on a 0 to 100 scale.
- Output price
- Gemini 3.1 Pro Preview Custom Tools $12.00 against GPT-5.3-Codex $14.00 per million output tokens, 1.2x apart.
- Context window
- Gemini 3.1 Pro Preview Custom Tools takes 1.05M tokens, GPT-5.3-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.
| Category | Gemini 3.1 Pro Preview Custom Tools | Bars | GPT-5.3-Codex | Ties |
|---|---|---|---|---|
| Agentic work | 0 | 1 | ||
| All shared boards | 0 | 1 |
CodingDirectional onlySix of these boards feed the Vibe Coding Index12 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | GPT-5.3-Codex | Leader |
|---|---|---|---|
| LMArena WebDev | Not measured | 1407 | Only GPT-5.3-Codex measured |
| LiveCodeBench (Vals AI) | Not measured | 87.3% | Only GPT-5.3-Codex measured |
| SWE-bench Verified (Vals AI) | Not measured | 78.0% | Only GPT-5.3-Codex measured |
| Vibe Code Bench (Vals AI) | Not measured | 61.8% | Only GPT-5.3-Codex measured |
| IOI (Vals AI) | Not measured | 53.8% | Only GPT-5.3-Codex measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 53.0% | Only GPT-5.3-Codex measured |
| Terminal-Bench | Not measured | 78.4% | Only GPT-5.3-Codex measured |
| WeirdML | Not measured | 79.3% | Only GPT-5.3-Codex measured |
| ALE-Bench | Not measured | 1655.2 | Only GPT-5.3-Codex measured |
| LMArena WebDev: React | Not measured | 1395 | Only GPT-5.3-Codex measured |
| LMArena WebDev: HTML | Not measured | 1422 | Only GPT-5.3-Codex measured |
| LMArena WebDev: from an image | Not measured | 1443 | Only GPT-5.3-Codex measured |
| Neither model has a result on the other 27 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index2 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | GPT-5.3-Codex | Leader |
|---|---|---|---|
| AA Intelligence Index | Not measured | 32.5 | Only GPT-5.3-Codex measured |
| Epoch Capabilities Index | Not measured | 157.1 | Only GPT-5.3-Codex measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | GPT-5.3-Codex | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | Not measured | 1032 | Only GPT-5.3-Codex measured |
| Design Arena: agents building full-stack apps | Not measured | 983 | Only GPT-5.3-Codex measured |
| Design Arena: agents building mobile apps | Not measured | 1054 | Only GPT-5.3-Codex measured |
| Design Arena: agents building Android apps | Not measured | 1084 | Only GPT-5.3-Codex measured |
| Design Arena: agents building Godot games | Not measured | 1124 | Only GPT-5.3-Codex measured |
| τ²-Bench Telecom | Not measured | 86.0% | Only GPT-5.3-Codex measured |
| METR time horizons | Not measured | 74.5% | Only GPT-5.3-Codex measured |
| Vending-Bench 2 | $3,774 | $5,940 | GPT-5.3-Codex |
| Neither model has a result on the other 33 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index2 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | GPT-5.3-Codex | Leader |
|---|---|---|---|
| GPQA Diamond (Artificial Analysis run) | Not measured | 91.5% | Only GPT-5.3-Codex measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 42.5% | Only GPT-5.3-Codex measured |
| Neither model has a result on the other 20 boards here | |||
MathNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | GPT-5.3-Codex | Leader |
|---|---|---|---|
| Neither model has a result on 13 boards here | |||
KnowledgeNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | GPT-5.3-Codex | Leader |
|---|---|---|---|
| Neither model has a result on 18 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | GPT-5.3-Codex | Leader |
|---|---|---|---|
| Design Arena: websites | Not measured | 1163 | Only GPT-5.3-Codex measured |
| Design Arena: UI components | Not measured | 1137 | Only GPT-5.3-Codex measured |
| Design Arena: game dev | Not measured | 1161 | Only GPT-5.3-Codex measured |
| Design Arena: data viz | Not measured | 1164 | Only GPT-5.3-Codex measured |
| Design Arena: 3D | Not measured | 1008 | Only GPT-5.3-Codex measured |
| Design Arena: all code categories | Not measured | 1145 | Only GPT-5.3-Codex measured |
| Design Arena: SVG | Not measured | 1129 | Only GPT-5.3-Codex measured |
| Design Arena: ASCII art | Not measured | 1152 | Only GPT-5.3-Codex measured |
| Neither model has a result on the other 1 board here | |||
GeneralDirectional onlyPublic boards, shown as published, kept out of the index2 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | GPT-5.3-Codex | Leader |
|---|---|---|---|
| IFBench | Not measured | 75.4% | Only GPT-5.3-Codex measured |
| Long context reasoning (AA-LCR) | Not measured | 83.3% | Only GPT-5.3-Codex measured |
| Neither model has a result on the other 44 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | GPT-5.3-Codex | 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
Gemini 3.1 Pro Preview Custom Tools costs less
Repository review
50K input + 3K output tokens
GPT-5.3-Codex costs less
Agent loop
200K input + 10K output tokens
GPT-5.3-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.
| Specification | Google Gemini 3.1 Pro Preview Custom Tools | OpenAI GPT-5.3-Codex |
|---|---|---|
| Maker | OpenAI | |
| Weights | No public weights listed | No public weights listed |
| Released | February 25, 2026 | February 24, 2026 |
| Context window | 1.05M | 400K |
| Input $/Mtok | $2.00 | $1.75 |
| Output $/Mtok | $12.00 | $14.00 |
| Coding index | Not benchmarked | 60.0 |
| Independent measurements behind it | 0 | 3 |
| Cost per solved task | Not computable | $0.59 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Gemini 3.1 Pro Preview Custom Tools better than GPT-5.3-Codex for coding?
Only GPT-5.3-Codex has a coding score, 60.0 on the Vibe Coding Index; Gemini 3.1 Pro Preview Custom Tools has none, so the two cannot be ranked on coding. Pick Gemini 3.1 Pro Preview Custom Tools for output tokens 1.2x cheaper ($12.00 vs $14.00 per million) and a larger context window (1.05M against 400K tokens).
Which is cheaper, Gemini 3.1 Pro Preview Custom Tools or GPT-5.3-Codex?
Gemini 3.1 Pro Preview Custom Tools costs $2.00 per million input tokens and $12.00 per million output tokens; GPT-5.3-Codex costs $1.75 and $14.00. Cost per solved task is known for GPT-5.3-Codex only.
Which has the bigger context window, Gemini 3.1 Pro Preview Custom Tools or GPT-5.3-Codex?
Gemini 3.1 Pro Preview Custom Tools, with 1.05M tokens against 400K.
How many benchmarks is the Gemini 3.1 Pro Preview Custom Tools vs GPT-5.3-Codex comparison based on?
1 benchmarks have a result for both models as of October 21, 2026. Gemini 3.1 Pro Preview Custom Tools's coding index rests on 0 independent benchmarks and GPT-5.3-Codex's on 3. Where only one model has a result, the page says so instead of naming a winner.