AI chatbots can give different answers to the same question depending on timing, phrasing, or device.

These shifts happen because AI models are susceptible to context — even small changes in wording or updates can alter their tone and output.

For example, systems like GPT-4 are trained to be safe and reliable.

Human feedback fine-tuning makes them cautious by default, avoiding edgy humor or controversy unless prompted.

If ChatGPT feels overly polite or neutral, that’s intentional — it’s designed to prioritize helpfulness and professionalism.

AI Platform	Responses Differ When Logged In	Desktop vs Mobile Differences	Additional Response Factors
Perplexity	Yes. Logged-out users default to Perplexity’s proprietary model; logged-in or paid users can select Claude or GPT-4-class models. However, even logged-in users may get downgraded responses for “simple” prompts to reduce costs .	Minor UI and context differences. The web app integrates directly with browser pages on desktop, offering contextual summarization not available on mobile .	Model selection (Claude, GPT-4, or in-house model), search integration, incognito mode, and conversation complexity affect results .
ChatGPT	Yes. Logged-in users can access GPT-4 or GPT-4o; logged-out users are limited to GPT-4o-mini with reduced reasoning quality .	The desktop app supports file uploads and voice input (with GPT-4o). Mobile responses can vary slightly due to network speed and voice transcription context .	Model version, memory features (for Plus users), temporary chat mode, and plugin/browser integration influence responses .
Claude	Yes. Logged-out (API-free) use isn’t available; users must sign in. Response tone and memory persistence change with account login and organization context .	Minimal. Web and mobile are nearly identical, but context carry-over (like document handling) is smoother on desktop.	Model type (Instant vs Sonnet vs Opus), chat history enabled/disabled, and file upload context significantly alter responses .
Grok	Yes. Uses X.com/OAuth sign-in; stored account data (Google/Twitter) changes personalization and memory. Logging out often resets context, which causes different tone and continuity .	Slight interface differences. Mobile often prioritizes humor and brevity vs longer analytical replies on desktop .	Access level (basic vs premium), social feed integration, and stored preferences from user tweets affect tone and output .
Google AI (Gemini / Search Overviews)	Generally no. AI Overviews now produce nearly identical output whether signed in or not, though personalization and ads change when signed in .	Desktop allows linked source previews and context panes; mobile focuses on single-column simplified summaries .	Search history, personalization settings, region, and SafeSearch level affect summaries .
Microsoft Copilot (Edge / Windows / Office)	Yes. Logged-in users access corporate, enterprise, or personal Microsoft Graph data; logged-out users receive general web responses only .	Desktop integrates with Edge/Office apps. Mobile Copilot (in Bing app) gives shorter, task-driven answers.	Account type (Microsoft 365 vs free Bing), enterprise data access, permission scopes, and connected sources (Outlook, SharePoint) strongly affect output .

Key Observations

Login state directly controls model version and personalization level for Perplexity, ChatGPT, Claude, Grok, and Copilot.
Device type mainly affects interface and contextual breadth, not the underlying model reasoning (except Grok’s humor-tuned replies).
Other important factors influencing variability include:

- Model/version availability (e.g., GPT-4o vs 4o-mini).
- Subscription tier or enterprise access (notably ChatGPT Plus and Copilot 365).
- Context understanding from browser integration (Perplexity, Copilot).
- User personalization or memory settings (ChatGPT, Claude).
- Region and content policies (Google AI AI, Grok).