ZMIME
Comparison · 2 models · Updated Oct 4, 2026

Gemini 3.1 Pro Preview vs GPT-5.3 Codex

Gemini 3.1 Pro Preview comes out ahead, 68 to 64 on our weighted score, and it is the cheaper option too.

  1. Our pick

    Google

    Gemini 3.1 Pro Preview

    Released Feb 19, 2026

    68/100
    • ECI154.8
    • Price$2.00 / $12.00
    • Context1.05M
    Full specs Remove Gemini 3.1 Pro Preview

  2. OpenAI

    GPT-5.3 Codex

    Released Feb 5, 2026

    64/100
    • ECI156.8
    • Price$1.75 / $14.00
    • Context400K
    Full specs Remove GPT-5.3 Codex

  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 68/100 against GPT-5.3 Codex (64). It leads on inputs & features and context window. GPT-5.3 Codex wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGPT-5.3 CodexCapabilities Index (ECI): GPT-5.3 Codex 156.8 · Gemini 3.1 Pro Preview 154.8
  • Lowest priceGemini 3.1 Pro PreviewGemini 3.1 Pro Preview $4.50 · GPT-5.3 Codex $4.81 per 1M tokens (3:1 blend)
  • Longest contextGemini 3.1 Pro PreviewGemini 3.1 Pro Preview 1,048,576 · GPT-5.3 Codex 400,000 tokens
  • Widest inputsGemini 3.1 Pro PreviewGemini 3.1 Pro Preview: Text, Images, PDFs, Audio, Video · GPT-5.3 Codex: Text, Images, PDFs
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGemini 3.1 Pro PreviewGPT-5.3 Codex
CapabilityCapabilities Index (ECI)50%8487
Price25%1918
Inputs & features15%10080
Context window10%6144
Overall100%68/10064/100
02 — Side by side

Every spec in one table

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

Gemini 3.1 Pro Preview vs GPT-5.3 Codex specifications side by side
SpecificationGemini 3.1 Pro PreviewGoogleGPT-5.3 CodexOpenAI
Capability
Capabilities Index (ECI)154.8156.8 (best)
ECI rank#31 of 148#18 of 148 (best)
GPQA DiamondGraduate-level science questions94.4%—
FrontierMath Tiers 1–3Research-level mathematics59.7%—
OTIS Mock AIME 2024–2025Competition mathematics95.6%—
SWE-bench VerifiedFixing real GitHub issues75.6% (best)74.8%
SimpleQA VerifiedShort factual questions73.5%—
Price per million tokens
Input$2.00$1.75 (best)
Output$12.00 (best)$14.00
Cached input$0.20$0.175 (best)
Blended (3:1)$4.50 (best)$4.81
Long-context rateOver 200K: $4.00 / $18.00Same rate
Price sourceOfficial Google APIOfficial OpenAI API
Limits
Context window1,048,576 tokens (best)400,000 tokens
Max output65,536 tokens128,000 tokens (best)
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioYesNo
VideoYesNo
ReasoningYeslow · medium · highYeslow · medium · high · xhigh
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDgemini-3.1-pro-previewgpt-5.3-codex
API providers26 (best)19
ReleasedFeb 19, 2026Feb 5, 2026
Knowledge cutoffJan 2025Aug 31, 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.

  • Gemini 3.1 Pro Preview$44.00
  • GPT-5.3 Codex$45.50
04 — Questions

Which should you choose?

Which is better: Gemini 3.1 Pro Preview or GPT-5.3 Codex?

Gemini 3.1 Pro Preview is the better all-round choice, scoring 68/100 against GPT-5.3 Codex (64). It leads on inputs & features and context window. GPT-5.3 Codex wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Gemini 3.1 Pro Preview or GPT-5.3 Codex?

Gemini 3.1 Pro Preview is cheaper at $2.00 input / $12.00 output per million tokens (official Google API price). GPT-5.3 Codex costs $1.75 input / $14.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $4.50 per million tokens for Gemini 3.1 Pro Preview versus $4.81 for GPT-5.3 Codex (1.1× as much).

Which scores higher on benchmarks?

GPT-5.3 Codex scores higher on the Capabilities Index (ECI): GPT-5.3 Codex 156.8 (#18 of 148) and Gemini 3.1 Pro Preview 154.8 (#31 of 148). The confidence ranges of the top two overlap (153.5–160.8 vs 152.6–157.3), so treat the gap as small. On individual benchmarks: SWE-bench Verified — Gemini 3.1 Pro Preview 75.6%, GPT-5.3 Codex 74.8%.

Which is better for coding?

Gemini 3.1 Pro Preview resolves more real GitHub issues on SWE-bench Verified: Gemini 3.1 Pro Preview 75.6% and GPT-5.3 Codex 74.8%. 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-5.3 Codex. Maximum output per response: Gemini 3.1 Pro Preview up to 65,536, GPT-5.3 Codex up to 128,000 tokens.

Which can read images, PDFs, audio or video?

Gemini 3.1 Pro Preview accepts text, images, PDFs, audio and video; GPT-5.3 Codex accepts text, images and PDFs. Gemini 3.1 Pro Preview handles the widest range of inputs.

Are any of these open source?

No. Gemini 3.1 Pro Preview and GPT-5.3 Codex 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-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: Gemini 3.1 Pro Preview Jan 2025, GPT-5.3 Codex Aug 31, 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

Related comparisons