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Comparison · 2 models · Updated Oct 4, 2026

GPT-5-Codex vs Gemini 3.1 Pro Preview

Gemini 3.1 Pro Preview comes out ahead, 52 to 42 on our weighted score, though GPT-5-Codex is 24% cheaper per token.

  1. OpenAI

    GPT-5-Codex

    Released Sep 15, 2025

    42/100
    • ECI—
    • Price$1.25 / $10.00
    • Context400K
    Full specs Remove GPT-5-Codex
  2. Our pick

    Google

    Gemini 3.1 Pro Preview

    Released Feb 19, 2026

    52/100
    • ECI154.8
    • Price$2.00 / $12.00
    • Context1.05M
    Full specs Remove Gemini 3.1 Pro Preview

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Gemini 3.1 Pro Preview is our pick

Gemini 3.1 Pro Preview is the better all-round choice, scoring 52/100 against GPT-5-Codex (42). It leads on inputs & features and context window. GPT-5-Codex wins on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

  • CapabilityNot enough dataNo independent benchmark covers every model here yet
  • Lowest priceGPT-5-CodexGPT-5-Codex $3.44 · Gemini 3.1 Pro Preview $4.50 per 1M tokens (3:1 blend)
  • Longest contextGemini 3.1 Pro PreviewGemini 3.1 Pro Preview 1,048,576 · GPT-5-Codex 400,000 tokens
  • Widest inputsGemini 3.1 Pro PreviewGPT-5-Codex: Text, Images · Gemini 3.1 Pro Preview: Text, Images, PDFs, Audio, Video
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGPT-5-CodexGemini 3.1 Pro Preview
Price50%2419
Inputs & features30%70100
Context window20%4461
Overall100%42/10052/100

Left out because at least one model lacks the data: capability. The remaining weights were rescaled.

02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

GPT-5-Codex vs Gemini 3.1 Pro Preview specifications side by side
SpecificationGPT-5-CodexOpenAIGemini 3.1 Pro PreviewGoogle
Capability
Capabilities Index (ECI)—154.8
ECI rank—#31 of 148
GPQA DiamondGraduate-level science questions—94.4%
FrontierMath Tiers 1–3Research-level mathematics—59.7%
OTIS Mock AIME 2024–2025Competition mathematics—95.6%
SWE-bench VerifiedFixing real GitHub issues—75.6%
SimpleQA VerifiedShort factual questions—73.5%
Price per million tokens
Input$1.25 (best)$2.00
Output$10.00 (best)$12.00
Cached input—$0.20
Blended (3:1)$3.44 (best)$4.50
Long-context rateSame rateOver 200K: $4.00 / $18.00
Price sourceMedian of 3 providersOfficial Google API
Limits
Context window400,000 tokens1,048,576 tokens (best)
Max output128,000 tokens (best)65,536 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsNoYes
AudioNoYes
VideoNoYes
ReasoningYesYeslow · medium · high
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model ID—gemini-3.1-pro-preview
API providers326 (best)
ReleasedSep 15, 2025Feb 19, 2026
Knowledge cutoffSep 30, 2024Jan 2025
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • GPT-5-Codex$32.50
  • Gemini 3.1 Pro Preview$44.00
04 — Questions

Which should you choose?

Which is better: GPT-5-Codex or Gemini 3.1 Pro Preview?

Gemini 3.1 Pro Preview is the better all-round choice, scoring 52/100 against GPT-5-Codex (42). It leads on inputs & features and context window. GPT-5-Codex wins on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

Which is cheaper, GPT-5-Codex or Gemini 3.1 Pro Preview?

GPT-5-Codex is cheaper at $1.25 input / $10.00 output per million tokens (median across 3 API providers). Gemini 3.1 Pro Preview costs $2.00 input / $12.00 output per million tokens (official Google API price). At a typical mix of three input tokens to one output token, that is $3.44 per million tokens for GPT-5-Codex versus $4.50 for Gemini 3.1 Pro Preview (1.3× as much).

Which scores higher on benchmarks?

There is no independent benchmark that covers both models yet. GPT-5-Codex has not been scored yet and Gemini 3.1 Pro Preview has an ECI of 154.8.

Which is better for coding?

There are no published SWE-bench Verified results for GPT-5-Codex yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Both support tool calling for agent workflows.

Which has the bigger context window?

Gemini 3.1 Pro Preview has the largest context window at 1,048,576 tokens, against 400,000 for GPT-5-Codex. Maximum output per response: GPT-5-Codex up to 128,000, Gemini 3.1 Pro Preview up to 65,536 tokens.

Which can read images, PDFs, audio or video?

GPT-5-Codex accepts text and images; Gemini 3.1 Pro Preview accepts text, images, PDFs, audio and video. Gemini 3.1 Pro Preview handles the widest range of inputs.

Are any of these open source?

No. GPT-5-Codex and Gemini 3.1 Pro Preview are proprietary and only available through APIs and apps.

Which is newer?

Gemini 3.1 Pro Preview is the newest, released Feb 19, 2026. GPT-5-Codex came out Sep 15, 2025. Knowledge cutoff: GPT-5-Codex Sep 30, 2024, Gemini 3.1 Pro Preview Jan 2025.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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