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Perplexity is an AI answer engine that combines live web search with large language models to deliver cited, up-to-date answers. Instead of a blank chat, it returns sourced summaries with follow-up questions, making it a popular replacement for traditional search. Pro mode taps frontier models and deeper research, and its API exposes the same search-grounded answers.

ChatGPT is OpenAI's flagship conversational AI, powering hundreds of millions of weekly users across web, mobile and API. Built on the GPT-4o and GPT-5 family of models, it handles text, images, voice and code in a single interface. With browsing, data analysis, custom GPTs and a vast plugin ecosystem, it remains the default assistant for most knowledge workers.

Poe by Quora is an aggregator that gives access to dozens of AI models — including GPT, Claude, Gemini and many image models — through a single subscription. Users can chat with multiple bots, build custom bots and compare outputs side by side. It is ideal for people who want one place to reach many models without juggling separate accounts.

Gemini is Google's natively multimodal model family, deeply integrated across Search, Workspace, Android and the Pixel line. Its standout feature is an enormous context window of up to one to two million tokens, ideal for analysing long videos, codebases and document sets. Gemini blends Google's real-time knowledge with strong reasoning and is available free in many products.