ChatGPT doesn’t allow you to expand the input field like Gemini does.
Gemini allows you to press the button at the top-right corner to expand the input field
Why?
My best guess right now is about cost.
- Smaller input boxes subtly push people to write shorter messages, which saves compute. At ChatGPT’s scale, that’s not pocket change (they claimed to have 800M weekly active users as of Oct 2025).
- Google can afford the opposite. Its vertically integrated AI stack makes inference cheaper, so it can offer the “expand to write more” nicety without sweating the bill.
- Sidenote: Claude, Grok, and DeepSeek also don’t have this expand feature. Same logic probably.
And maybe this is about user experience: shorter prompts mean the model has less to juggle: less context, faster answers, fewer chances to get lost. But I’m not sure.
But ChatGPT allows that on mobile
It’s a hassle to type on phone, which nudges people toward writing fewer words.