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Head-to-head comparison

GPT-5.3-Codex vs GPT-5.5

GPT-5.3-Codex (OpenAI) and GPT-5.5 (OpenAI) 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 17 August 2026

As of 17 August 2026, GPT-5.5 holds the stronger ModelCap Index position (#8 vs #20); GPT-5.3-Codex is 2.1× cheaper per output token ($14.00/1M vs $30.00/1M); and GPT-5.5 offers the longer context window (1M vs 400K tokens).

Which should you choose?

Choose GPT-5.3-Codex if…

  • API cost matters — $14.00/1M output tokens against $30.00/1M, about 2.1× cheaper.
  • your workload is prompt-heavy — input tokens cost $1.75/1M against $5.00/1M.

Choose GPT-5.5 if…

  • you want the stronger overall ModelCap Index position — #8 against #20 (76.9 vs 66.4 points).
  • you need the longer context window — 1M tokens against 400K.
  • you want provider choice — 3 listed API providers against 2.
  • Artificial Analysis Intelligence Index is your yardstick — 56.3 against 45.5.
  • you want the more recently listed model — GPT-5.5 was listed 24 April 2026, GPT-5.3-Codex 24 February 2026.

GPT-5.3-Codex vs GPT-5.5: specs, pricing and context

Specification comparison of GPT-5.3-Codex and GPT-5.5
FieldGPT-5.3-CodexOpenAIGPT-5.5OpenAI
ModelCap Index position#20#8
Index score66.476.9
EvidenceMeasuredMeasured
Input price / 1M tokens$1.75$5.00
Output price / 1M tokens$14.00$30.00
Context window400K tokens1M tokens
Max output tokens128K128K
API providers listed23
Weight accessAPI onlyAPI only
Input modalitiesText, Image, FileFile, Image, Text
First listed24 February 202624 April 2026
PublisherOpenAIOpenAI

Evidence: 1 public benchmark observation across 1 board · 6 public benchmark observations across 6 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: GPT-5.3-Codex vs GPT-5.5

Public benchmark boards where GPT-5.3-Codex or GPT-5.5 has a published result
BoardGPT-5.3-CodexGPT-5.5Leads
Arena codingArena (LMArena)—15201513–1526HighOnly one result
LMArena AgentLMArena—8.9%7.9%–9.9%X-HighOnly one result
ARC-AGI-2ARC Prize Foundation—85.0%X-HighOnly one result
ARC-AGI-3ARC Prize Foundation—0.4%HighOnly one result
Artificial Analysis Intelligence IndexArtificial Analysis45.5intelligence-index56.3intelligence-indexGPT-5.5

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-5.3-Codex vs GPT-5.5: common questions

Is GPT-5.3-Codex better than GPT-5.5?

GPT-5.5 ranks higher on the ModelCap Index as of 17 August 2026: #8 against #20. 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.

Is GPT-5.3-Codex cheaper than GPT-5.5?

GPT-5.3-Codex is cheaper on output tokens: $14.00/1M against $30.00/1M. Input tokens are $1.75/1M for GPT-5.3-Codex and $5.00/1M for GPT-5.5. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens.

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

GPT-5.5 has the larger context window: 1M tokens against 400K.

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

The two models do not share a coding benchmark board on ModelCap yet, so no head-to-head coding score is published; the ModelCap Index position is the closest overall signal.

Are GPT-5.3-Codex and GPT-5.5 open-weight models?

GPT-5.3-Codex: API only. GPT-5.5: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run GPT-5.3-Codex and GPT-5.5?

ModelCap currently lists 2 API providers for GPT-5.3-Codex and 3 for GPT-5.5, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this GPT-5.3-Codex vs GPT-5.5 comparison?

Every figure comes from the sealed ModelCap dataset published 17 August 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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