GLM-5.1 vs GPT-5.3 Codex
GPT-5.3 Codex comes out ahead, 64 to 57 on our weighted score, though GLM-5.1 is 2.2× cheaper per token.
Z.ai (Zhipu)GLM-5.1
57/100- ECI149.9
- Price$1.40 / $4.40
- Context200K
- Our pick
OpenAIGPT-5.3 Codex
64/100- ECI156.8
- Price$1.75 / $14.00
- Context400K
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Make it a three-way comparison.
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 CodexGLM-5.1: Text · GPT-5.3 Codex: Text, Images, PDFs
- Self-hostingGLM-5.1Publishes downloadable weights
| Measure | Weight | GLM-5.1 | GPT-5.3 Codex |
|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 78 | 87 |
| Price | 25% | 34 | 18 |
| Inputs & features | 15% | 45 | 80 |
| Context window | 10% | 32 | 44 |
| Overall | 100% | 57/100 | 64/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GLM-5.1Z.ai (Zhipu) | GPT-5.3 CodexOpenAI |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | 149.9 | 156.8 (best) |
| ECI rank | #51 of 148 | #18 of 148 (best) |
| 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 issues | 74.2% | 74.8% (best) |
| SimpleQA VerifiedShort factual questions | 34.0% | — |
| Price per million tokens | ||
| Input | $1.40 (best) | $1.75 |
| Output | $4.40 (best) | $14.00 |
| Cached input | $0.26 | $0.175 (best) |
| Blended (3:1) | $2.15 (best) | $4.81 |
| Long-context rate | Same rate | Same rate |
| Price source | Official Z.AI API | Official OpenAI API |
| Limits | ||
| Context window | 200,000 tokens | 400,000 tokens (best) |
| Max output | 131,072 tokens (best) | 128,000 tokens |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | No | Yes |
| PDFs | No | Yes |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yes | Yeslow · medium · high · xhigh |
| Tool calling | Yes | Yes |
| Structured output | Yes | Yes |
| Availability | ||
| Weights | Open | Proprietary |
| API model ID | glm-5.1 | gpt-5.3-codex |
| API providers | 40 (best) | 19 |
| Released | Apr 7, 2026 | Feb 5, 2026 |
| Knowledge cutoff | — | Aug 31, 2025 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GLM-5.1$22.80
- GPT-5.3 Codex$45.50
Which should you choose?
Which is better: GLM-5.1 or GPT-5.3 Codex?
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, GLM-5.1 or GPT-5.3 Codex?
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: GLM-5.1 up to 131,072, GPT-5.3 Codex up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GLM-5.1 accepts text; GPT-5.3 Codex accepts text, images and PDFs. 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.
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