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Head-to-head comparison

GPT-5.5 vs GLM 5.3 Flash

GPT-5.5 (OpenAI) and GLM 5.3 Flash (Z.ai) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 24 October 2026

As of 24 October 2026, GPT-5.5 holds the stronger ModelCap Index position (#16 vs #24); GLM 5.3 Flash is 60× cheaper per output token ($0.50/1M vs $30.00/1M); and GLM 5.3 Flash ships open weights.

Which should you choose?

Choose GPT-5.5 if…

  • you want the stronger overall ModelCap Index position — #16 against #24 (79.6 vs 77.3 points).
  • Arena text is your yardstick — 1482 against 1476.
  • ARC-AGI-2 is your yardstick — 85.0% against 65.8%.

Choose GLM 5.3 Flash if…

  • API cost matters — $0.50/1M output tokens against $30.00/1M, about 60× cheaper.
  • your workload is prompt-heavy — input tokens cost $0.15/1M against $5.00/1M.
  • you want to self-host: GLM 5.3 Flash ships open weights while GPT-5.5 is no linked weights.
  • you want provider choice — 34 listed API providers against 3.
  • Arena coding is your yardstick — 1525 against 1519.
  • you want the more recently listed model — GLM 5.3 Flash was listed 26 August 2026, GPT-5.5 24 April 2026.

GPT-5.5 vs GLM 5.3 Flash: specs, pricing and context

Specification comparison of GPT-5.5 and GLM 5.3 Flash
FieldGPT-5.5OpenAIGLM 5.3 FlashZ.ai
ModelCap Index position#16#24
Index score79.677.3
EvidenceMeasuredMeasured
Input price / 1M tokens$5.00$0.15
Output price / 1M tokens$30.00$0.50
Context window1M tokens1M tokens
Declared route output cap128K944K
API providers listed334
Weight accessNo linked weightsOpen weights
Input modalitiesFile, Image, TextText, Image, Video
First listed24 April 202626 August 2026
PublisherOpenAIZ.ai

Evidence: 4 public benchmark observations across 4 boards · 4 public benchmark observations across 4 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: GPT-5.5 vs GLM 5.3 Flash

Public benchmark boards where GPT-5.5 or GLM 5.3 Flash has a published result
BoardGPT-5.5GLM 5.3 FlashLeads
Arena textArena (LMArena)14821478–1485High14761471–1481Not reportedGPT-5.5
Arena codingArena (LMArena)15191513–1525High15251518–1532GLM 5.3 Flash
LMArena AgentLMArena—-1.8%-2.4%–-1.1%Only one result
ARC-AGI-2ARC Prize Foundation85.0%X-High65.8%MaxGPT-5.5
ARC-AGI-3ARC Prize Foundation0.4%High—Only one result
AA Intelligence IndexArtificial Analysis—41.8ReasoningOnly one result
AA Terminal-Bench 2.1Artificial Analysis—84.3%ReasoningOnly one result
AA Humanity's Last ExamArtificial Analysis—39.9%ReasoningOnly one result
Terminal-Bench 4.0Terminal-Bench (Laude Institute)—35.8%32.2%–39.3%Claude Code · NoneOnly one result
Terminal-Bench 2.1 Terminus 2Terminal-Bench78.0X-High—Only one result
WildClawBench OpenClawWildClawBench58.2—Only one result

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

GPT-5.5 vs GLM 5.3 Flash: common questions

Is GPT-5.5 better than GLM 5.3 Flash?

GPT-5.5 ranks higher on the ModelCap Index as of 24 October 2026: #16 against #24. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.

Is GPT-5.5 cheaper than GLM 5.3 Flash?

GLM 5.3 Flash is cheaper on output tokens: $0.50/1M against $30.00/1M. Input tokens are $5.00/1M for GPT-5.5 and $0.15/1M for GLM 5.3 Flash. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $25.00 for GPT-5.5 versus $0.55 for GLM 5.3 Flash. GLM 5.3 Flash costs 97.8% less in this scenario. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.

Which has the bigger context window, GPT-5.5 or GLM 5.3 Flash?

Both publish a 1M-token context window. OpenRouter catalogue or provider-endpoint declaration. Limits can vary by provider and prompt length; a model-wide maximum has not been independently verified.

Which is better for coding, GPT-5.5 or GLM 5.3 Flash?

Arena coding: GPT-5.5 1519, GLM 5.3 Flash 1525 — GLM 5.3 Flash leads.

Are GPT-5.5 and GLM 5.3 Flash open-weight models?

GPT-5.5: No linked weights. GLM 5.3 Flash: Open weights. Open weights mean the checkpoint can be downloaded and self-hosted under its licence. A missing weight link does not identify every API or chat product that offers a model.

Where can I run GPT-5.5 and GLM 5.3 Flash?

ModelCap currently lists 3 API providers for GPT-5.5 and 34 for GLM 5.3 Flash, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this GPT-5.5 vs GLM 5.3 Flash comparison?

Every figure and ModelCap Index position comes from the same published snapshot dated 24 October 2026. Publication and page updates happen separately; use the snapshot date shown on the page.

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