This in-depth guide covers ChatGPT from its launch to the present: versions and timelines, how it works, features, pricing across free and paid plans, key tools, accuracy and limitations, safety, and practical workflows for work and study—updated to August 2025.
What Is ChatGPT?
ChatGPT is OpenAI’s conversational AI assistant that understands and generates text, and in recent generations also supports images, audio, and structured tool use for tasks like web browsing, file analysis, and code execution. It launched publicly on November 30, 2022, using the GPT‑3.5 model, and has progressed through GPT‑4, GPT‑4o, the o‑series reasoning models, GPT‑4.1/4.5, and now GPT‑5 in 2025.
Timeline: Major Releases and What Changed
- Nov 30, 2022 — ChatGPT (GPT‑3.5): Initial public preview fine‑tuned from GPT‑3.5, trained in early 2022.
- Mar 14, 2023 — GPT‑4: Introduced via ChatGPT Plus with stronger reasoning and broader capabilities.
- Nov 2023 — GPT‑4 Turbo: Larger context window (128,000 tokens) to handle longer inputs.
- May 13, 2024 — GPT‑4o: “Omni” multimodal model; real‑time text, image, audio handling; higher free usage than prior, with higher limits for paid.
- Jul 2024 — GPT‑4o mini: Smaller, cheaper, used widely in ChatGPT and replaced 3.5 in July 2024 version.
- Sep–Dec 2024 — o1 preview/o1/o1‑mini and o1‑pro: “Thinking before answering” reasoning focus; strong performance in math/competitive programming/science.
- Jan 2025 — o3‑mini and o3‑mini‑high: Successors emphasizing structured reasoning and variable “effort.”
- Feb 2025 — GPT‑4.5: Larger model with reduced hallucinations; described as the last “non‑chain‑of‑thought” model.
- Apr 14, 2025 — GPT‑4.1 and 4.1‑mini (API first): 4.1‑mini beats 4o on many benchmarks while being lighter; later added to ChatGPT.
- Apr 16, 2025 — o3 and o4‑mini: Reasoning models with agentic tool use across search, Python, file analysis, vision, image generation, and more.
- Apr 2025 — Platform updates: Memory with Search; expanded tool autonomy; plus tool orchestration improvements.
- Apr 30, 2025 — GPT‑4 retired from ChatGPT and replaced by GPT‑4o in the app (API availability separate); voice mode remains powered by 4o.
- Aug 7, 2025 — GPT‑5: Flagship model replacing previous models across free and paid tiers in ChatGPT; also in Copilot and API.
Note: OpenAI iterated quickly in 2025; exact availability can differ between ChatGPT app and API.
Current State (August 2025)
- GPT‑5 is the flagship ChatGPT model in the app for free and paid users, replacing GPT‑4/4o/4.1/4.5/o‑series for most chats across tiers, according to Wikipedia and OpenAI announcements.
- Chats created with older models may be auto‑mapped to GPT‑5 equivalents; some specialized variants (e.g., “GPT‑5‑Thinking/Pro”) are noted for higher tiers.
- Voice mode still relies on GPT‑4o under the hood for some functionalities even as GPT‑5 becomes default for text multimodal interactions.
Plans and Pricing: Free vs Paid
OpenAI offers multiple ChatGPT plans with different limits and tools.
- Free: $0; access to ChatGPT with core model (currently GPT‑5), subject to usage caps.
- Plus: $20/month; priority access at peak, faster responses, higher limits on advanced models/tools, including voice, image generation, file uploads/analysis, custom GPTs, and Deep Research (where available).
- Pro: $200/month; for power users and advanced workloads with much higher caps and premium model access.
- Team: $25/user/month annually ($30 month‑to‑month); collaboration features and management for small teams.
- Enterprise: Custom pricing for large organizations (SAML SSO, governance, admin controls, dedicated capacity).
OpenAI notes that Plus/Team have monthly billing; Team also supports annual billing, while Plus does not advertise annual discounts. Regional taxes may apply; third‑party trackers summarize typical VAT‑inclusive ranges but final billing is per OpenAI.
Models: Capabilities by Generation
- GPT‑3.5: Strong general chat; limited multimodality; now discontinued in ChatGPT app after 4o mini replacement.
- GPT‑4/Turbo: Better reasoning and coding; Turbo introduced 128k context for long documents; retired in ChatGPT UI by April 2025.
- GPT‑4o: Natively multimodal (text, images, audio), faster response; set benchmarks in non‑English and vision; high limits for paid tiers.
- o‑series (o1, o3, o4‑mini): Trained to “think longer,” agentically use and combine tools (search, Python, vision, image generation, file/canvas) and handle complex, multi‑step tasks.
- GPT‑4.1/4.1‑mini: API‑first release; 4.1‑mini matches or beats 4o on many benchmarks at smaller size.
- GPT‑4.5: Larger with reduced hallucinations; transition before GPT‑5.
- GPT‑5: OpenAI’s newest “smartest, fastest, most useful” model with built‑in reasoning; replaces prior models across ChatGPT; available broadly including Copilot and API.
Core Features in ChatGPT (2025)
- Multimodal interactions: Text, images, and audio inputs/outputs; real‑time voice; 4o and successors power voice and vision tasks.
- Web browsing: Searches via third‑party providers; now integrated with memory to tailor queries when enabled.
- File uploads and analysis: Use Python for data processing, charting, and complex file reasoning within the app.
- Custom GPTs: Create and use tailored assistants with instructions, knowledge, and tool permissions.
- Deep Research and Agentic Tool Use: o‑series and GPT‑5 can choose when to browse, code, or analyze files and stitch results end‑to‑end.
- Memory: Optional feature that lets ChatGPT remember preferences and context across sessions, now extended to inform search.
- Personalities: Multiple response styles (Default, Cynic, Robot, etc.) selectable in settings.
Getting Started: Setup and First Use
- Create an account at ChatGPT and log in; the free plan starts immediately with usage caps.
- Upgrade by profile > Upgrade Plan to access Plus/Pro/Team benefits; Team requires multiple seats or annual commitment per seat.
- Enable features: In Settings, toggle Memory, manage Custom GPTs, and review Data Controls and privacy options.
- Try voice: Use mobile or desktop voice mode; voice uses GPT‑4o for real‑time responsiveness.
- Use tools: Attach files, switch to “Browse” when offered, and let the model decide tool sequencing on complex tasks, especially with reasoning models.
How ChatGPT Works (High Level)
- Foundation model pretraining on large corpora, then supervised fine‑tuning and reinforcement learning from human feedback (RLHF) to make responses helpful and safe.
- Multimodality: GPT‑4o and successors natively process and align text, vision, and audio, enabling unified context handling.
- Reasoning models: o‑series and GPT‑5 emphasize longer internal “thinking,” tool use planning, and structured outputs under time/effort budgets.
- Context windows: Expanded in Turbo and subsequent models (e.g., 128k in GPT‑4 Turbo) to handle long documents and multi‑file analysis.
Practical Use Cases and Workflows
- Knowledge work: Drafts, summaries, meeting notes, RFPs; enable browsing for current data; save Memory for preferences where appropriate.
- Coding: Code generation, debugging, tests; use file uploads for repos; leverage tool use for dependency checks and script execution.
- Data analysis: Upload CSV/PDF; request Python analysis and visualizations; ask for reproducible steps and outputs.
- Research: Use Deep Research or browsing; request citations and syntheses; ask the model to show tool steps and collected evidence.
- Creative work: Storyboards, image generation, scripts; adjust Personality or temperature via “Creative” styles when available.
- Education: Explanations at levels (beginner to expert); worked solutions; caution with hallucinations; verify with sources using browse.
Accuracy, Hallucinations, and Limits
- Hallucinations: Models can still generate incorrect or fabricated information; GPT‑4.5 reduced rates, and reasoning models improve reliability, but verification remains essential for critical use.
- Recency: Browsing helps retrieve current facts; app‑resident knowledge can lag without search.
- Privacy and data: Review Settings > Data Controls; enterprise plans include governance and admin features for compliance.
- Tool autonomy: While o‑series and GPT‑5 plan tool usage, user oversight is recommended for consequential actions.
Safety and Policies
- OpenAI employs safety mitigations and policy guidelines; models are tuned to avoid harmful content and respect usage policies.
- Voice and agent features prioritize user consent, transparency, and reversible actions within the app environment.
Comparison Table: Free vs Plus vs Pro vs Team
Prices exclude local taxes; Plus has no annual discount; Team supports annual billing; Enterprise is custom.
Version Highlights at a Glance
- GPT‑4o: Real‑time multimodal, fast, strong non‑English and vision performance.
- o‑series: Deep reasoning and agentic tool use across search, Python, files, vision, image gen, canvas.
- GPT‑4.1‑mini: Small model that rivals 4o on many benchmarks.
- GPT‑5: Replaces prior models in ChatGPT; built‑in reasoning with expert‑level assistance focus.
Frequently Asked Questions
- Is GPT‑4 still available in ChatGPT? OpenAI retired GPT‑4 from the ChatGPT app as of April 30, 2025; GPT‑4o replaced it in the UI, with GPT‑5 now the default model in August 2025.
- Does voice use GPT‑5? Voice mode remains powered by GPT‑4o, while text/multimodal chat defaults to GPT‑5 in the app.
- Is Plus worth it? If needing higher limits, faster responses, voice, file analysis, custom GPTs, and research/browsing built‑ins, Plus adds clear value for individuals.
- How do Team and Pro differ? Team is per‑seat with collaboration/admin features; Pro maximizes individual usage headroom and premium access at a higher monthly cost.
Where to Track Updates
- OpenAI ChatGPT Release Notes provide granular changes to models, features, and deprecations.
- OpenAI’s blog and model pages announce major models (4.1, o3/o4‑mini, GPT‑5) and capabilities.
- Wikipedia’s ChatGPT page maintains a consolidated version history and status snapshot.
Expert Tips
- Turn on Memory to personalize interactions and improve multi‑session continuity; it now also informs browsing queries.
- Ask the model to “show its steps” when using tools: it can explain when it searched, analyzed files, or wrote code for transparency.
- For long documents, explicitly request sectioned summaries and a final synthesis to minimize omissions within context limits.
- When accuracy is critical, enable browsing and ask for cited sources; verify claims beyond the model’s internal knowledge.
