OpenAI launched GPT-4.5 on February 27, 2025, as a research preview of its largest general-purpose chat model at the time. It emphasized broad knowledge, natural conversation, writing and creative work rather than deliberate chain-of-thought reasoning. GPT-4.5 is no longer available in ChatGPT, and its API preview is deprecated; OpenAI recommends GPT-4.1 or o3 for most new projects.
When did GPT-4.5 launch?
OpenAI announced GPT-4.5 on February 27, 2025. The launch described it as a research preview and initially made it available to ChatGPT Pro users and developers worldwide, with staged access planned for Plus, Team, Enterprise and Edu customers.
OpenAI positioned GPT-4.5 as its strongest chat model then, saying it scaled pre-training and post-training with more compute and data, alongside architecture and optimization changes. The intended benefits were broader knowledge, better pattern recognition, improved instruction following, fewer hallucinations, more nuance and more natural collaboration.
What was GPT-4.5?
GPT-4.5 was a general-purpose, non-chain-of-thought model. In practical terms, it generated an answer directly instead of exposing a separate reasoning process before responding. OpenAI contrasted that design with reasoning models such as o1 and o3-mini.
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The model was meant to be a stronger foundation for conversation, writing, brainstorming, coding assistance and later tool-using systems. OpenAI described pre-training and reasoning as complementary: GPT-4.5 supplied broad learned knowledge and interaction quality, while reasoning models were aimed at spending more computation on difficult multi-step problems.
Where was GPT-4.5 available at launch?
ChatGPT
Pro subscribers could select GPT-4.5 on the web, mobile and desktop apps. OpenAI planned a staged rollout to other paid plans rather than an immediate release to every account.
Developer APIs
The preview was offered in Chat Completions, Assistants and Batch APIs. The launch listed function calling, Structured Outputs, streaming, system messages and image inputs as supported capabilities.
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GPT-4.5’s published benchmark results
OpenAI published the following 2025 results and identified the displayed values as its best internal performance figures. They are launch-era evaluations, not a guarantee of present-day product behavior.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11| Evaluation | GPT-4.5 | GPT-4o | o3-mini (high) |
|---|---|---|---|
| GPQA | 71.4% | 53.6% | 79.7% |
| AIME 2024 | 36.7% | 9.3% | 87.3% |
| MMMLU | 85.1% | 81.5% | 81.1% |
| MMMU | 74.4% | 69.1% | not stated |
| SWE-Lancer Diamond | 32.6% | 23.3% | 10.8% |
| SWE-Bench Verified | 38.0% | 30.7% | 61.0% |
The pattern matters more than any single score: GPT-4.5 improved on GPT-4o across these published general-knowledge, multimodal and software benchmarks, while o3-mini was substantially stronger on the mathematics-heavy AIME test and SWE-Bench Verified. GPT-4.5 was not presented as a replacement for every reasoning workload.
Was GPT-4.5 better for writing and creativity?
OpenAI’s design goal favored writing and creative collaboration. Its training and optimization work targeted nuance, natural conversation, instruction following and understanding user intent. That made GPT-4.5 a logical choice for drafting, editing, ideation, tone matching and open-ended dialogue when an immediate, fluent response mattered more than a visible reasoning pass.
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Those strengths should not be confused with guaranteed factual accuracy. GPT-4.5 could still produce incorrect information, and the published benchmark figures do not establish that it was best for every writing genre or professional fact-checking requirement.
GPT-4.5 compared with other OpenAI models
| Decision factor | GPT-4.5 | GPT-4o | o1/o3-mini |
|---|---|---|---|
| Primary design | General chat, knowledge, creativity and natural interaction | General-purpose multimodal model | Deliberate reasoning for difficult, multi-step tasks |
| Reasoning behavior | Non-chain-of-thought; responds directly | Direct response model | Reasoning-focused models that spend more computation before answering |
| Writing and conversation | OpenAI emphasized nuance, intent understanding and collaboration | Strong general conversational baseline | Usually selected when reasoning depth is the priority |
| Developer status | Preview deprecated | Availability depends on the current API catalog | OpenAI recommends o3 for many current use cases |
This is a role-based comparison, not a claim that one model wins every prompt. Choose a current supported model, then test it against your own prompts, latency limits, tool calls and quality checks.
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The listed GPT-4.5 Preview snapshot was gpt-4.5-preview-2025-02-27. The official model information lists a 128,000-token context window, a maximum output of 16,384 tokens, an October 1, 2023 knowledge cutoff, streaming, function calling and Structured Outputs.
| Token type | Listed price | Qualification |
|---|---|---|
| Input | $75 per 1 million tokens | GPT-4.5 Preview API price |
| Cached input | $37.50 per 1 million tokens | GPT-4.5 Preview API price |
| Output | $150 per 1 million tokens | GPT-4.5 Preview API price |
The API page now labels GPT-4.5 Preview as deprecated and recommends GPT-4.1 or o3 for most uses. Treat the prices above as the published listing for that deprecated preview, not as a promise that new access can be created.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why was GPT-4.5 deprecated?
OpenAI’s current pages establish the product status, but do not give a single detailed technical explanation for the deprecation. GPT-4.5 was launched as a research preview, and its API listing is now marked deprecated with migration guidance toward GPT-4.1 or o3. That indicates a product-line transition rather than evidence that the model suddenly stopped working.
ChatGPT retirement is separately recorded in OpenAI’s release notes: GPT-4.5 was retired from ChatGPT on June 27, 2026, following a 30-day sunset period. A ChatGPT retirement does not automatically mean that every API identifier disappears on the same date, so developers should check the model’s current API status before planning a migration.
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Safety findings at launch
OpenAI’s GPT-4.5 system card reported post-mitigation preparedness ratings of Medium for CBRN and persuasion, and Low for cybersecurity and model autonomy. OpenAI said it found no significant increase in safety risk compared with existing models. It also stated that only models with a post-mitigation score of Medium or below could be deployed.
These ratings describe the evaluation and mitigation framework used for deployment; they are not a guarantee that model outputs are harmless. Applications still need access controls, monitoring, content filters and human review appropriate to their risk.
What should developers use instead?
- Inventory GPT-4.5 calls. Record the model identifier, context size, output limits, tool calls, structured schemas and any image-input use.
- Try GPT-4.1 for general workloads. OpenAI’s deprecated-model page recommends it as a default alternative for many applications.
- Try o3 for reasoning-heavy workloads. Use it when multi-step analysis, mathematical work or difficult coding is more important than immediate conversational style.
- Retest quality and cost. Compare representative prompts, tool-call success, latency, refusal behavior, token usage and downstream validation before switching production traffic.
- Keep safeguards in place. A replacement model still needs the same schema validation, retries, logging, privacy controls and human escalation paths.
Bottom line
GPT-4.5 was OpenAI’s February 2025 attempt to push general-purpose chat quality through larger-scale training rather than chain-of-thought reasoning. It was especially aimed at knowledge-rich, fluent and creative interaction, but it carried a high API price and was never the strongest option for every reasoning benchmark. As of June 27, 2026 it is retired from ChatGPT, and its API preview is deprecated, so new work should generally start with GPT-4.1 or o3 and validate the choice on real workloads.
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