ChatGPT, Claude, Gemini and Copilot: what each one actually is, who makes it, what it's for, and how to tell them apart

What is the difference between ChatGPT, Claude, Gemini and Copilot?

ChatGPT is OpenAI's consumer and developer assistant, built on OpenAI's GPT models [1]. Claude is Anthropic's assistant, built on Anthropic's own Claude models [2]. Gemini is Google's assistant, built on Google's Gemini models [4]. Copilot is Microsoft's brand for AI assistance across its products, historically built on OpenAI models under a partnership, now increasingly mixing in Microsoft's own [5]. All four are chat interfaces to an underlying large language model; the differences that matter are which company controls the model, what each is tuned for, and where each shows up, in a browser tab, an IDE, or Office.

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I use several of these daily in production work and teach students to choose deliberately rather than defaulting to whichever name they heard first. My longer framework for choosing a model provider for an actual application, not a chat tab, is on the portfolio [11].

These are four companies' front doors to their own models. The chat window is the least interesting part; the model behind it is what actually differs. Pranjul Rathour

What is ChatGPT, and who makes it?

ChatGPT is OpenAI's assistant product, the interface most people first meet a large language model through [1]. It runs on OpenAI's GPT-series models and has grown from a text chat window into a multimodal assistant that reads images, browses, runs code, and increasingly acts as an agent. "Is ChatGPT down" usually means an OpenAI-side outage or degraded service, checkable on OpenAI's own status page rather than guessed at [7], though a browser extension conflict or a regional network issue can look identical from the user's side.

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What is Claude, and what is Claude Code?

Claude is Anthropic's assistant, built on Anthropic's own Claude model family, generally positioned around careful reasoning, longer documents, and steerable behaviour [2][9]. Claude Code is a distinct product from the chat assistant: an agentic coding tool that runs in a terminal or editor, reads and edits a real codebase, runs commands, and works through multi-step engineering tasks rather than just answering questions in a chat window [3]. Anthropic's newer "Claude Cowork"-style collaborative features extend this agent pattern to broader work tasks beyond code.

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What is Gemini, and what is Copilot?

Gemini is Google's assistant, built on Google's own Gemini models, integrated across Google Search, Workspace and Android [4]. Copilot is Microsoft's umbrella brand for AI assistance woven through Windows, Office, and GitHub; GitHub Copilot specifically is the coding-completion and chat assistant inside an IDE, historically powered substantially by OpenAI's models under the Microsoft-OpenAI partnership, with Microsoft's own models increasingly part of the mix [5]. "Why is Copilot down" or "not working" is almost always a GitHub or Microsoft service issue, an extension needing a restart, or an expired sign-in, checkable the same way as any outage, on the provider's status page first.

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What is Codex, and how does it compare to Claude Code?

Codex is OpenAI's agentic coding product, in the same category as Claude Code: an AI system that works directly in a codebase, running commands and making multi-file changes rather than only chatting [6]. The comparison that matters for choosing between them is less "which is smarter" in the abstract and more which integrates with your existing workflow, editor, and CI, and which model family's coding behaviour you have personally found more reliable on your kind of codebase, since both improve on overlapping but not identical benchmarks release to release.

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Is Ollama a competitor to these, and is it free?

Not directly. Ollama is a tool for running open-weight models, Llama, Mistral, Gemma, Qwen and others, on your own machine, entirely free and offline [8]. ChatGPT, Claude, Gemini and Copilot are hosted products built on closed or semi-closed models you access through an account and, for heavy use, a subscription or API bill. Ollama is the local, self-hosted alternative to all of them for tasks where privacy, cost, or offline access matter more than having the single most capable model available.

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How do I choose which one to use for a task?

For coding inside a real project, a coding agent, Claude Code or Codex, beats a general chat window because it can actually read and run your code. For long documents or careful step-by-step reasoning, compare Claude and the others on the specific document, since strengths shift by release. For anything tied into Google's ecosystem, Gemini's integration wins on convenience. For anything tied into Microsoft's ecosystem, Copilot wins the same way. For a quick one-off question, whichever is already open in a tab is the right answer; the differences matter for sustained work, not a single query.

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What mistakes do people make comparing these assistants?

Assuming "AI" is one thing and any assistant should behave like any other. Blaming your account for what is a provider-wide outage, or the reverse, assuming an outage when the problem is a browser extension. Using a general chat assistant for a coding agent's job, pasting code back and forth by hand when a coding agent would read the repository directly. Picking a favourite once and never re-checking as models change every few months. The fix for all of these is the same: know which product you are actually using and what it is built for.

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Where should I start?

Try the same real task, a piece of code, a document, a question you actually have, on two of these assistants this week and compare the answers yourself rather than trusting a ranking. For a workshop that teaches students to evaluate AI tools rather than default to whichever is trending, email pranjulrathour41@gmail.com or use pranjulrathour.scult.in/invite.

Pranjul Rathour

GenAI Engineer · Kanpur, Uttar Pradesh, India

GenAI engineer and AI product builder with 2+ years shipping production-grade AI systems: RAG pipelines, fine-tuned LLMs, hybrid retrieval and multi-modal apps across vision, speech and OCR, architected end to end from ingestion to deployment. Leads engineering for SCULT INDIA's 14-member team, founded the 500+ member TechVerse Enclave community and has mentored 200+ students. Three hackathon first prizes: Changethon 2025 (IIT Roorkee), Product Genesis at Vividhotsava 2025 (CSJMU Kanpur) and BYTEBATTLE (MeetKats).

Open to GenAI roles, hackathon judging, mentorship sessions and guest talks at colleges. Email pranjulrathour41@gmail.com.

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