Model Comparison

GPT-5.1 Codex vs Kimi K3Which is better in 2026?

Comparing GPT-5.1 Codex and Kimi K3 across benchmarks, pricing, and capabilities.

Verdict: GPT-5.1 Codex vs Kimi K3 — which is better?

GPT-5.1 Codex (by OpenAI) and Kimi K3 (by Moonshot AI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

On price, GPT-5.1 Codex is roughly 1.7x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Kimi K3 also accepts a larger context window (1,048,576 input tokens), making it the stronger choice for long documents and large codebases.

Choose GPT-5.1 Codex if…

  • cost matters — it's about 1.7x cheaper per token

Choose Kimi K3 if…

  • you process long inputs — it offers a 1,048,576 token context window
  • you want the most recent training data — it shipped Jul 2026

Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

GPT-5.1 Codex and Kimi K3don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

GPT-5.1 Codex costs less

For input processing, GPT-5.1 Codex ($1.25/1M tokens) is 2.4x cheaper than Kimi K3 ($3.00/1M tokens).

For output processing, GPT-5.1 Codex ($10.00/1M tokens) is 1.5x cheaper than Kimi K3 ($15.00/1M tokens).

In conclusion, Kimi K3 is more expensive than GPT-5.1 Codex.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Sat Jul 25 2026 • llm-stats.com
OpenAI
GPT-5.1 Codex
Input tokens$1.25
Output tokens$10.00
Best providerOpenAI
Moonshot AI
Kimi K3
Input tokens$3.00
Output tokens$15.00
Best providerUnknown Organization
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Kimi K3 accepts 1,048,576 input tokens compared to GPT-5.1 Codex's 400,000 tokens. Kimi K3 can generate longer responses up to 1,048,576 tokens, while GPT-5.1 Codex is limited to 128,000 tokens.

OpenAI
GPT-5.1 Codex
Input400,000 tokens
Output128,000 tokens
Moonshot AI
Kimi K3
Input1,048,576 tokens
Output1,048,576 tokens
Sat Jul 25 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both GPT-5.1 Codex and Kimi K3 support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

GPT-5.1 Codex

Text
Images
Audio
Video

Kimi K3

Text
Images
Audio
Video

Release Timeline

When each model was launched

GPT-5.1 Codex was released on 2025-11-19, while Kimi K3 was released on 2026-07-16.

Kimi K3 is 8 months newer than GPT-5.1 Codex.

GPT-5.1 Codex

Nov 19, 2025

8 months ago

Kimi K3

Jul 16, 2026

1 weeks ago

7mo newer

Knowledge Cutoff

When training data ends

GPT-5.1 Codex has a documented knowledge cutoff of 2024-09-30, while Kimi K3's cutoff date is not specified.

We can confirm GPT-5.1 Codex's training data extends to 2024-09-30, but cannot make a direct comparison without Kimi K3's cutoff date.

GPT-5.1 Codex

Sep 2024

Kimi K3

—

Provider Availability

GPT-5.1 Codex is available from OpenAI. Kimi K3 is available from Moonshot AI.

GPT-5.1 Codex

openai logo
OpenAI
Input Price:Input: $1.25/1MOutput Price:Output: $10.00/1M

Kimi K3

moonshot logo
Unknown Organization
Input Price:Input: $3.00/1MOutput Price:Output: $15.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Less expensive input tokens
Less expensive output tokens
Moonshot AI
Larger context window (1,048,576 tokens)
Has open weights

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.1 Codex and Kimi K3 side-by-side, then vote on the output you prefer.

GPT-5.1 Codex
✓ Preferred
Kimi K3
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.1 Codex
Moonshot AI
Kimi K3

FAQ

Common questions about GPT-5.1 Codex vs Kimi K3.

Which is better, GPT-5.1 Codex or Kimi K3?

GPT-5.1 Codex (OpenAI) and Kimi K3 (Moonshot AI) each have strengths in different areas. Compare their benchmark scores, pricing, context windows, and capabilities above to determine which fits your needs.

How does GPT-5.1 Codex compare to Kimi K3 in benchmarks?

GPT-5.1 Codex scores SWE-Bench Verified: 73.7%, SWE-Lancer: 66.3%, Terminal-Bench 2.0: 52.8%. Kimi K3 scores MathVision: 97.8%, DeepSearchQA: 95.0%, GPQA: 93.5%, CharXiv-R: 91.3%, BrowseComp: 91.2%.

Is GPT-5.1 Codex cheaper than Kimi K3?

GPT-5.1 Codex is 2.4x cheaper for input tokens. GPT-5.1 Codex costs $1.25/M input and $10.00/M output via openai. Kimi K3 costs $3.00/M input and $15.00/M output via moonshot.

What are the context window sizes for GPT-5.1 Codex and Kimi K3?

GPT-5.1 Codex supports 400K tokens and Kimi K3 supports 1.0M tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-5.1 Codex and Kimi K3?

Key differences include context window (400K vs 1.0M), input pricing ($1.25 vs $3.00/M), licensing (Proprietary vs Unknown). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.1 Codex and Kimi K3?

GPT-5.1 Codex is developed by OpenAI and Kimi K3 is developed by Moonshot AI.

Related comparisons