GPT-5.3 Codex vs GLM-5.1 vs Gemini 3.1 Pro Preview
Gemini 3.1 Pro Preview comes out ahead, 68 to 64 and 57 on our weighted score, though GLM-5.1 is 2.1× cheaper per token.
OpenAIGPT-5.3 Codex
64/100- ECI156.8
- Price$1.75 / $14.00
- Context400K
Z.ai (Zhipu)GLM-5.1
57/100- ECI149.9
- Price$1.40 / $4.40
- Context200K
- Our pick
GoogleGemini 3.1 Pro Preview
68/100- ECI154.8
- Price$2.00 / $12.00
- Context1.05M
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) and GLM-5.1 (57). It leads on inputs & features and context window. GPT-5.3 Codex wins on capability. 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 · Gemini 3.1 Pro Preview 154.8 · GLM-5.1 149.9
- Lowest priceGLM-5.1GLM-5.1 $2.15 · Gemini 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 · GLM-5.1 200,000 tokens
- Widest inputsGemini 3.1 Pro PreviewGPT-5.3 Codex: Text, Images, PDFs · GLM-5.1: Text · Gemini 3.1 Pro Preview: Text, Images, PDFs, Audio, Video
- Self-hostingGLM-5.1Publishes downloadable weights
| Measure | Weight | GPT-5.3 Codex | GLM-5.1 | Gemini 3.1 Pro Preview |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 87 | 78 | 84 |
| Price | 25% | 18 | 34 | 19 |
| Inputs & features | 15% | 80 | 45 | 100 |
| Context window | 10% | 44 | 32 | 61 |
| Overall | 100% | 64/100 | 57/100 | 68/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.3 CodexOpenAI | GLM-5.1Z.ai (Zhipu) | Gemini 3.1 Pro PreviewGoogle |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 156.8 (best) | 149.9 | 154.8 |
| ECI rank | #18 of 148 (best) | #51 of 148 | #31 of 148 |
| GPQA DiamondGraduate-level science questions | — | 89.9% | 94.4% (best) |
| FrontierMath Tiers 1–3Research-level mathematics | — | 36.8% | 59.7% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | — | 93.3% | 95.6% (best) |
| SWE-bench VerifiedFixing real GitHub issues | 74.8% | 74.2% | 75.6% (best) |
| SimpleQA VerifiedShort factual questions | — | 34.0% | 73.5% (best) |
| Price per million tokens | |||
| Input | $1.75 | $1.40 (best) | $2.00 |
| Output | $14.00 | $4.40 (best) | $12.00 |
| Cached input | $0.175 (best) | $0.26 | $0.20 |
| Blended (3:1) | $4.81 | $2.15 (best) | $4.50 |
| Long-context rate | Same rate | Same rate | Over 200K: $4.00 / $18.00 |
| Price source | Official OpenAI API | Official Z.AI API | Official Google API |
| Limits | |||
| Context window | 400,000 tokens | 200,000 tokens | 1,048,576 tokens (best) |
| Max output | 128,000 tokens | 131,072 tokens (best) | 65,536 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | No | Yes |
| PDFs | Yes | No | Yes |
| Audio | No | No | Yes |
| Video | No | No | Yes |
| Reasoning | Yeslow · medium · high · xhigh | Yes | Yeslow · medium · high |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Open | Proprietary |
| API model ID | gpt-5.3-codex | glm-5.1 | gemini-3.1-pro-preview |
| API providers | 19 | 40 (best) | 26 |
| Released | Feb 5, 2026 | Apr 7, 2026 | Feb 19, 2026 |
| Knowledge cutoff | Aug 31, 2025 | — | Jan 2025 |
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
- Gemini 3.1 Pro Preview$44.00
Which should you choose?
Which is better: GPT-5.3 Codex, GLM-5.1 or Gemini 3.1 Pro Preview?
Gemini 3.1 Pro Preview is the better all-round choice, scoring 68/100 against GPT-5.3 Codex (64) and GLM-5.1 (57). It leads on inputs & features and context window. GPT-5.3 Codex wins on capability. 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, GLM-5.1 or Gemini 3.1 Pro Preview?
GLM-5.1 is cheaper at $1.40 input / $4.40 output per million tokens (official Z.AI API price). Gemini 3.1 Pro Preview costs $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 $2.15 per million tokens for GLM-5.1 versus $4.50 for Gemini 3.1 Pro Preview (2.1× as much) and $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), Gemini 3.1 Pro Preview 154.8 (#31 of 148) and GLM-5.1 149.9 (#51 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%, GLM-5.1 74.2%.
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%, GPT-5.3 Codex 74.8% and GLM-5.1 74.2%. All three 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 and 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, Gemini 3.1 Pro Preview up to 65,536 tokens.
Which can read images, PDFs, audio or video?
GPT-5.3 Codex accepts text, images and PDFs; GLM-5.1 accepts text; 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?
GLM-5.1 publishes its weights and can be self-hosted; GPT-5.3 Codex and Gemini 3.1 Pro Preview is proprietary.
Which is newer?
GLM-5.1 is the newest, released Apr 7, 2026. Gemini 3.1 Pro Preview came out Feb 19, 2026; GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: GPT-5.3 Codex Aug 31, 2025, 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.
