GPT-5.3 Chat vs GPT-5.5 Instant
GPT-5.3 Chat and GPT-5.5 Instant are closely matched at 29.6 and 32.4 on the LLM Stats Score. GPT-5.3 Chat is 2.3x cheaper per token.
OpenAI · OpenAI · Updated for 2026
Which is better?
GPT-5.3 Chat and GPT-5.5 Instant are closely matched on the overall LLM Stats Score at 29.6 and 32.4.
In the 2 individual benchmarks reported for both models, GPT-5.3 Chat wins 2; this is a narrower head-to-head signal than the composite indexes.
On price, GPT-5.3 Chat is roughly 2.3x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.5 Instant also accepts a larger context window (400,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose GPT-5.3 Chat
- you value its reported benchmark strengths — it wins 2 of 2 exact shared results
- cost matters — it's about 2.3x cheaper per token
Choose GPT-5.5 Instant
- you process long inputs — it offers a 400,000 token context window
- you want the most recent training data — it shipped May 2026
At a glance
The differences that matter most.
Individual benchmarks
2 reported for GPT-5.3 Chat · 9 for GPT-5.5 Instant
GPT-5.3 Chat outperforms in 2 benchmarks (HealthBench, HealthBench Hard), while GPT-5.5 Instant is better at 0 benchmarks.
GPT-5.3 Chat significantly outperforms across most benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-5.3 Chat ($1.75/1M tokens) is 2.9x cheaper than GPT-5.5 Instant ($5.00/1M tokens).
For output processing, GPT-5.3 Chat ($14.00/1M tokens) is 2.1x cheaper than GPT-5.5 Instant ($30.00/1M tokens).
In conclusion, GPT-5.5 Instant is more expensive than GPT-5.3 Chat.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.5 Instant accepts 400,000 input tokens compared to GPT-5.3 Chat's 128,000 tokens. GPT-5.5 Instant can generate longer responses up to 128,000 tokens, while GPT-5.3 Chat is limited to 16,384 tokens.
Input capabilities
Documented input modalities across available providers
Both GPT-5.3 Chat and GPT-5.5 Instant support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
GPT-5.3 Chat
GPT-5.5 Instant
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
GPT-5.3 Chat was released on 2026-03-04, while GPT-5.5 Instant was released on 2026-05-05.
GPT-5.5 Instant is 2 months newer than GPT-5.3 Chat.
Mar 4, 2026
6 months ago
May 5, 2026
4 months ago
2mo newerKnowledge Cutoff
When training data ends
Both models have the same knowledge cutoff date of 2025-08-31.
They should have similar awareness of historical events and information up to this date.
Aug 2025
Aug 2025
Provider Availability
GPT-5.3 Chat is available from OpenAI. GPT-5.5 Instant is available from OpenAI.
GPT-5.3 Chat
GPT-5.5 Instant
Outputs Comparison
Judge for yourself.
Run your own prompts against GPT-5.3 Chat and GPT-5.5 Instant side-by-side, then vote on the output you prefer.
FAQ
Common questions about GPT-5.3 Chat vs GPT-5.5 Instant.