OpenAI: GPT‑5.3 Instant API
GPT‑5.3 Instant significantly reduces unnecessary refusals, while toning down overly defensive or moralizing preambles before answering the question. When a useful answer is appropriate, the model should now provide one directly, staying focused on your question without unnecessary caveats. In practice, this means fewer dead ends and more directly helpful answers.
- Context window: 128,000 tokens
- Max output: 16,384 tokens
- Input: text, image
- Output: text
- Tool calling: Supported
- File input: Supported
- Released: 2026-03-03
- Knowledge cutoff: 2025-08-31
Frequently Asked Questions
What is the context window of GPT‑5.3 Instant?
GPT‑5.3 Instant supports a context window of up to 128,000 tokens.
Does GPT‑5.3 Instant support function calling?
Yes. GPT‑5.3 Instant supports tool / function calling.
What is the knowledge cutoff of GPT‑5.3 Instant?
The knowledge cutoff of GPT‑5.3 Instant is 2025-08-31.