Model · OpenAI · Text
GPT-5.5
OpenAI's former flagship — a unified general-purpose and reasoning model for coding and professional work. Superseded first by the GPT-6 generation and, in this catalog, by GPT-6.1 Sol (2026-09-29).
- Modality
- Text
- License
- Proprietary (Proprietary)
- Context window
- 1,050,000 tokens
- Released
- April 24, 2026
- Last verified
- October 28, 2026
- Runs locally
- No
- Also handles
- vision
Strengths
- ~1M-token context window (128k max output)
- Unified frontier model — strong general, coding, and reasoning in one
- December 2025 knowledge cutoff
Weaknesses
- Closed weights — API/product only
- Flagship pricing ($5 input / $30 output per MTok)
Try it
| Where | Type | Notes |
|---|---|---|
| OpenAI API | hosted-api | API key required |
| Azure OpenAI | hosted-api | Enterprise / regional |
| ChatGPT | product | Free / paid tiers |
Version history
- GPT-5.6 Luna Jul 2026 Deprecated
- GPT-5.6 Sol Jul 2026 Deprecated
- GPT-5.6 Terra Jul 2026 Deprecated
- GPT-5.5 Apr 2026 Current Deprecated
- GPT-5.4 mini Mar 2026 Deprecated
Official sources
- Model docs docs
- Announcement announcement
Change log
- — Deprecated — superseded by GPT-6.1 Sol (released 2026-09-29). Still served; not in OpenAI's deprecation table.
- — Verified current after the GPT-5.6 launch — GPT-5.6 is an additional frontier tier, not a replacement. OpenAI's deprecations page does not list GPT-5.5, and still names it as the recommended successor for o3, GPT-5, and the chat-latest snapshots. Release date corrected 2026-04-23 → 2026-04-24 per the API changelog.
- — Initial entry (2026-06-08 catalog refresh, Tier 3). Flagship released 2026-04-23; the successor OpenAI positions above GPT-4o and the o-series.
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