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Comparison · 2 models · Updated Oct 4, 2026

GPT-5.3 Codex vs GPT-5.1

GPT-5.3 Codex comes out ahead, 64 to 60 on our weighted score, though GPT-5.1 is 29% cheaper per token.

  1. Our pick

    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

  2. OpenAI

    GPT-5.1

    Released Nov 13, 2025

    60/100
    • ECI149.7
    • Price$1.25 / $10.00
    • Context400K
    Full specs Remove GPT-5.1

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

GPT-5.3 Codex is our pick

GPT-5.3 Codex is the better all-round choice, scoring 64/100 against GPT-5.1 (60). It leads on capability and inputs & features. GPT-5.1 wins on price. 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 · GPT-5.1 149.7
  • Lowest priceGPT-5.1GPT-5.1 $3.44 · GPT-5.3 Codex $4.81 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameGPT-5.3 Codex 400,000 · GPT-5.1 400,000 tokens
  • Widest inputsGPT-5.3 CodexGPT-5.3 Codex: Text, Images, PDFs · GPT-5.1: Text, Images
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGPT-5.3 CodexGPT-5.1
CapabilityCapabilities Index (ECI)50%8778
Price25%1824
Inputs & features15%8070
Context window10%4444
Overall100%64/10060/100
02 — Side by side

Every spec in one table

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

GPT-5.3 Codex vs GPT-5.1 specifications side by side
SpecificationGPT-5.3 CodexOpenAIGPT-5.1OpenAI
Capability
Capabilities Index (ECI)156.8 (best)149.7
ECI rank#18 of 148 (best)#52 of 148
GPQA DiamondGraduate-level science questions—87.6%
OTIS Mock AIME 2024–2025Competition mathematics—88.6%
SWE-bench VerifiedFixing real GitHub issues74.8% (best)68.0%
SimpleQA VerifiedShort factual questions—48.0%
Price per million tokens
Input$1.75$1.25 (best)
Output$14.00$10.00 (best)
Cached input$0.175$0.125 (best)
Blended (3:1)$4.81$3.44 (best)
Long-context rateSame rateSame rate
Price sourceOfficial OpenAI APIOfficial OpenAI API
Limits
Context window400,000 tokens400,000 tokens
Max output128,000 tokens128,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesNo
AudioNoNo
VideoNoNo
ReasoningYeslow · medium · high · xhighYeslow · medium · high
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDgpt-5.3-codexgpt-5.1
API providers1921 (best)
ReleasedFeb 5, 2026Nov 13, 2025
Knowledge cutoffAug 31, 2025Sep 30, 2024
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-5.3 Codex$45.50
  • GPT-5.1$32.50
04 — Questions

Which should you choose?

Which is better: GPT-5.3 Codex or GPT-5.1?

GPT-5.3 Codex is the better all-round choice, scoring 64/100 against GPT-5.1 (60). It leads on capability and inputs & features. GPT-5.1 wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, GPT-5.3 Codex or GPT-5.1?

GPT-5.1 is cheaper at $1.25 input / $10.00 output per million tokens (official OpenAI 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 $3.44 per million tokens for GPT-5.1 versus $4.81 for GPT-5.3 Codex (1.4× 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 GPT-5.1 149.7 (#52 of 148). Their confidence ranges do not overlap (153.5–160.8 vs 148.3–151.1), so the gap is a real one. On individual benchmarks: SWE-bench Verified — GPT-5.3 Codex 74.8%, GPT-5.1 68.0%.

Which is better for coding?

GPT-5.3 Codex resolves more real GitHub issues on SWE-bench Verified: GPT-5.3 Codex 74.8% and GPT-5.1 68.0%. Both support tool calling for agent workflows.

Which has the bigger context window?

GPT-5.3 Codex and GPT-5.1 share the same 400,000-token context window. Maximum output per response: GPT-5.3 Codex up to 128,000, GPT-5.1 up to 128,000 tokens.

Which can read images, PDFs, audio or video?

GPT-5.3 Codex accepts text, images and PDFs; GPT-5.1 accepts text and images. GPT-5.3 Codex handles the widest range of inputs.

Are any of these open source?

No. GPT-5.3 Codex and GPT-5.1 are proprietary and only available through APIs and apps.

Which is newer?

GPT-5.3 Codex is the newest, released Feb 5, 2026. GPT-5.1 came out Nov 13, 2025. Knowledge cutoff: GPT-5.3 Codex Aug 31, 2025, GPT-5.1 Sep 30, 2024.

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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