ChatGPT vs Claude vs Perplexity vs Gemini: what is the difference?

ChatGPT (OpenAI) = generalist leader, most versatile. Claude (Anthropic) = excellent for pro and legal, more rigorous. Perplexity = conversational search engine with mandatory citations. Gemini (Google) = embedded in Google Search, multimodal-native. Four signatures for four distinct usage profiles.

ChatGPT vs Claude vs Perplexity vs Gemini: what is the difference, according to PROEMA?

The four dominant answer engines in 2026 are not interchangeable. They differ in audience, retrieval logic and citation format. Knowing those differences is a prerequisite for any calibrated GEO strategy.

ChatGPT (OpenAI), the mainstream giant. 900 million weekly active users as of February 2026, over 2 billion daily queries (official OpenAI announcement, February 2026). 50 million paying subscribers. SearchGPT mode, launched late 2024 and rolled out in 2025, triggers the OAI-SearchBot crawler on every informational or freshness-sensitive query. Citation format: footer panel with 3 to 8 clickable links. Audience: mainstream, dominant in BE and FR.

Claude (Anthropic), the premium B2B engine. Smaller audience than ChatGPT but heavily over-represented among executives and developers (per Anthropic, more than a third of the Fortune 500 use Claude). Real-time crawl via Claude-SearchBot; citations sit in the footer with direct links. Claude is known to cite deeper and more secondary sources than ChatGPT, a strong fit for premium B2B verticals where the expert's authority matters most.

Perplexity, the citation-first engine. Estimated at 1.2 to 1.5 billion monthly queries by mid-2026, with > 800% YoY growth. Built from day one around citations: every answer points to 4 to 10 sources, numbered inline in the text. Dedicated crawler: PerplexityBot. Citation format: inline + footer. A sweet spot for brands with strong editorial capital.

Gemini (Google), the mass engine via AI Overviews. Google AI Overviews shows on 13% of all queries in Q1 2026, but climbs to 36-47% on informational queries (Europe, March 2026). Dedicated crawler: Google-Extended for training; retrieval still leans on the classic Google index (Googlebot). Citation format: « AI Overview » modules at the top of the SERP with a small set of linked sources. Coverage is exploding, projected at 60-65% of informational queries by end of 2026.

Practical takeaway. A serious GEO audit tests at least all four engines; ChatGPT-only became insufficient in 2026. The GEO Rocket portfolio tests six (the four plus Copilot Microsoft and Apple Intelligence) on the In-Depth panel. "A brand dominant in ChatGPT but absent from Perplexity usually has a press-citation deficit, absent from Claude an expert-depth deficit, and absent from Gemini AI Overviews a Schema.org structure deficit," observes Lorenzo Eeman, founder of PROEMA. Each engine surfaces a different diagnostic axis.

Counterintuitive finding. The "5W Citation Source" Q1 2026 audit (independent study covering 25,000 LLM answers) measured that Perplexity cites 5.7 sources per answer on average, ChatGPT search 2.9, Claude 1.6 and Gemini 3.2. Targeting "all LLMs" is lazy: Perplexity rewards source diversity, Claude concentrates on 1-2 canonical sources, ChatGPT splits via Bing as its retrieval ramp.