ZMIME
Comparison · 2 models · Updated Oct 4, 2026

GPT-5.3 Chat vs Kimi K3

Kimi K3 comes out ahead, 43 to 32 on our weighted score, though GPT-5.3 Chat is 20% cheaper per token.

  1. OpenAI

    GPT-5.3 Chat

    Released Mar 3, 2026Deprecated

    32/100
    • ECI—
    • Price$1.75 / $14.00
    • Context128K
    Full specs Remove GPT-5.3 Chat
  2. Our pick

    Moonshot AI

    Kimi K3

    Released Jul 16, 2026

    43/100
    • ECI157.6
    • Price$3.00 / $15.00
    • Context1.05M
    Full specs Remove Kimi K3

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Kimi K3 is our pick

Kimi K3 is the better all-round choice, scoring 43/100 against GPT-5.3 Chat (32). It leads on inputs & features and context window. GPT-5.3 Chat wins on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

  • CapabilityNot enough dataNo independent benchmark covers every model here yet
  • Lowest priceGPT-5.3 ChatGPT-5.3 Chat $4.81 · Kimi K3 $6.00 per 1M tokens (3:1 blend)
  • Longest contextKimi K3Kimi K3 1,048,576 · GPT-5.3 Chat 128,000 tokens
  • Widest inputsKimi K3GPT-5.3 Chat: Text, Images · Kimi K3: Text, Images, Video
  • Self-hostingKimi K3Publishes downloadable weights
How the score is built
MeasureWeightGPT-5.3 ChatKimi K3
Price50%1813
Inputs & features30%6080
Context window20%2461
Overall100%32/10043/100

Left out because at least one model lacks the data: capability. The remaining weights were rescaled.

02 — Side by side

Every spec in one table

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

GPT-5.3 Chat vs Kimi K3 specifications side by side
SpecificationGPT-5.3 ChatOpenAIKimi K3Moonshot AI
Capability
Capabilities Index (ECI)—157.6
ECI rank—#13 of 148
GPQA DiamondGraduate-level science questions—93.1%
FrontierMath Tiers 1–3Research-level mathematics—72.2%
OTIS Mock AIME 2024–2025Competition mathematics—97.2%
SimpleQA VerifiedShort factual questions—50.6%
Price per million tokens
Input$1.75 (best)$3.00
Output$14.00 (best)$15.00
Cached input$0.175 (best)$0.30
Blended (3:1)$4.81 (best)$6.00
Long-context rateSame rateSame rate
Price sourceOfficial OpenAI APIOfficial Moonshot AI API
Limits
Context window128,000 tokens1,048,576 tokens (best)
Max output16,384 tokens131,072 tokens (best)
Inputs and features
TextYesYes
ImagesYesYes
PDFsNoNo
AudioNoNo
VideoNoYes
ReasoningNoYeslow · high · max
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryOpen
API model IDgpt-5.3-chat-latestkimi-k3
API providers468 (best)
ReleasedMar 3, 2026Jul 16, 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 Chat$45.50
  • Kimi K3$60.00
04 — Questions

Which should you choose?

Which is better: GPT-5.3 Chat or Kimi K3?

Kimi K3 is the better all-round choice, scoring 43/100 against GPT-5.3 Chat (32). It leads on inputs & features and context window. GPT-5.3 Chat wins on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

Which is cheaper, GPT-5.3 Chat or Kimi K3?

GPT-5.3 Chat is cheaper at $1.75 input / $14.00 output per million tokens (official OpenAI API price). Kimi K3 costs $3.00 input / $15.00 output per million tokens (official Moonshot AI API price). At a typical mix of three input tokens to one output token, that is $4.81 per million tokens for GPT-5.3 Chat versus $6.00 for Kimi K3 (1.2× as much).

Which scores higher on benchmarks?

There is no independent benchmark that covers both models yet. GPT-5.3 Chat has not been scored yet and Kimi K3 has an ECI of 157.6.

Which is better for coding?

There are no published SWE-bench Verified results for GPT-5.3 Chat and Kimi K3 yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Both support tool calling for agent workflows.

Which has the bigger context window?

Kimi K3 has the largest context window at 1,048,576 tokens, against 128,000 for GPT-5.3 Chat. Maximum output per response: GPT-5.3 Chat up to 16,384, Kimi K3 up to 131,072 tokens.

Which can read images, PDFs, audio or video?

GPT-5.3 Chat accepts text and images; Kimi K3 accepts text, images and video. Kimi K3 handles the widest range of inputs.

Are any of these open source?

Kimi K3 publishes its weights and can be self-hosted; GPT-5.3 Chat is proprietary.

Which is newer?

Kimi K3 is the newest, released Jul 16, 2026. GPT-5.3 Chat came out Mar 3, 2026. Knowledge cutoff: GPT-5.3 Chat 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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