Gemini 3.5 Flash vs Gemini 3.1 Pro: What's the difference?

Google launched Gemini 3.5 Flash in May as the first model in the 3.5 family, built for speed and efficiency with a January 2025 knowledge cutoff. Gemini 3.1 Pro, released in February 2026, excels at deep reasoning and processing large volumes of information. Benchmarks show 3.5 Flash outperforms 3.1 Pro in several practical tasks.