ZMIME
Comparison · 2 models · Updated Oct 4, 2026

GPT-5.3 Codex vs GLM-5.1

GPT-5.3 Codex comes out ahead, 64 to 57 on our weighted score, though GLM-5.1 is 2.2× 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. Z.ai (Zhipu)

    GLM-5.1

    Released Apr 7, 2026

    57/100
    • ECI149.9
    • Price$1.40 / $4.40
    • Context200K
    Full specs Remove GLM-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 GLM-5.1 (57). It leads on capability, inputs & features and context window. GLM-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 · GLM-5.1 149.9
  • Lowest priceGLM-5.1GLM-5.1 $2.15 · GPT-5.3 Codex $4.81 per 1M tokens (3:1 blend)
  • Longest contextGPT-5.3 CodexGPT-5.3 Codex 400,000 · GLM-5.1 200,000 tokens
  • Widest inputsGPT-5.3 CodexGPT-5.3 Codex: Text, Images, PDFs · GLM-5.1: Text
  • Self-hostingGLM-5.1Publishes downloadable weights
How the score is built
MeasureWeightGPT-5.3 CodexGLM-5.1
CapabilityCapabilities Index (ECI)50%8778
Price25%1834
Inputs & features15%8045
Context window10%4432
Overall100%64/10057/100
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 GLM-5.1 specifications side by side
SpecificationGPT-5.3 CodexOpenAIGLM-5.1Z.ai (Zhipu)
Capability
Capabilities Index (ECI)156.8 (best)149.9
ECI rank#18 of 148 (best)#51 of 148
GPQA DiamondGraduate-level science questions—89.9%
FrontierMath Tiers 1–3Research-level mathematics—36.8%
OTIS Mock AIME 2024–2025Competition mathematics—93.3%
SWE-bench VerifiedFixing real GitHub issues74.8% (best)74.2%
SimpleQA VerifiedShort factual questions—34.0%
Price per million tokens
Input$1.75$1.40 (best)
Output$14.00$4.40 (best)
Cached input$0.175 (best)$0.26
Blended (3:1)$4.81$2.15 (best)
Long-context rateSame rateSame rate
Price sourceOfficial OpenAI APIOfficial Z.AI API
Limits
Context window400,000 tokens (best)200,000 tokens
Max output128,000 tokens131,072 tokens (best)
Inputs and features
TextYesYes
ImagesYesNo
PDFsYesNo
AudioNoNo
VideoNoNo
ReasoningYeslow · medium · high · xhighYes
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryOpen
API model IDgpt-5.3-codexglm-5.1
API providers1940 (best)
ReleasedFeb 5, 2026Apr 7, 2026
Knowledge cutoffAug 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.

  • GPT-5.3 Codex$45.50
  • GLM-5.1$22.80
04 — Questions

Which should you choose?

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

GPT-5.3 Codex is the better all-round choice, scoring 64/100 against GLM-5.1 (57). It leads on capability, inputs & features and context window. GLM-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 GLM-5.1?

GLM-5.1 is cheaper at $1.40 input / $4.40 output per million tokens (official Z.AI 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 $2.15 per million tokens for GLM-5.1 versus $4.81 for GPT-5.3 Codex (2.2× 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 GLM-5.1 149.9 (#51 of 148). Their confidence ranges do not overlap (153.5–160.8 vs 148.0–151.6), so the gap is a real one. On individual benchmarks: SWE-bench Verified — GPT-5.3 Codex 74.8%, GLM-5.1 74.2%.

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 GLM-5.1 74.2%. Both support tool calling for agent workflows.

Which has the bigger context window?

GPT-5.3 Codex has the largest context window at 400,000 tokens, against 200,000 for GLM-5.1. Maximum output per response: GPT-5.3 Codex up to 128,000, GLM-5.1 up to 131,072 tokens.

Which can read images, PDFs, audio or video?

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

Are any of these open source?

GLM-5.1 publishes its weights and can be self-hosted; GPT-5.3 Codex is proprietary.

Which is newer?

GLM-5.1 is the newest, released Apr 7, 2026. GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: 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

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