How AI-Powered Web Agents Are Redefining Browsing: A Deep Comparative Review

Background: From Viewer to Assistant

For over 30 years browsers only displayed pages, but AI has turned them into digital assistants capable of understanding requests and performing complex online tasks.

Web-Agent Landscape in 2025

2025 is dubbed the "AI Agent Year". Major products include OpenAI's ChatGPT Agent, China's Fellou, Perplexity's Comet, and The Browser Company's Dia.

Product Overviews

ChatGPT Agent : Unified agent system integrating Operator, Deep Research, and ChatGPT, using a perception‑reasoning‑execution pipeline with multimodal perception, o3 models for reasoning, and tools like visual and text browsers, terminal, and API. Runs in a cloud sandbox, achieving high scores on Humanity’s Last Exam (41.6% accuracy) and other benchmarks.

Fellou : Chinese agent emphasizing speed, using Deep Action and a hybrid shadow workspace to run tasks in parallel, achieving a 3.7‑minute average task time and 80% success on the Online‑Mind2web benchmark.

Perplexity Comet : Chromium‑based browser integrating Perplexity AI search, offering AI‑generated answers, contextual awareness across tabs, and integration with office tools. Uses a hybrid local‑cloud architecture.

Dia : AI‑native browser from The Browser Company, with AI dialogue in the address bar, cross‑tab context, customizable Skills, and local encryption, focusing on simplicity and user experience.

Benchmark Comparison

Key benchmarks include Humanity’s Last Exam, DSBench, SpreadsheetBench, WebArena, and BrowseComp. ChatGPT Agent leads with a total score of 90, Fellou follows with 52, while Comet and Dia score below 20 due to limited public data.

Technical Architecture

Three implementation models exist: AI‑native architecture (ChatGPT Agent, Fellou, Comet, Dia), deep integration into existing browsers, and AI plugins. The four products adopt the AI‑native model.

ChatGPT Agent Architecture

Cloud‑based virtual machine sandbox, multimodal perception, reasoning with GPT‑4o and CUA, four‑tool set, API connectors, strong security sandbox.

Fellou Architecture

Hybrid local‑cloud design with a shadow workspace, parallel execution of up to five windows, Eko framework for workflow definition, supports 50+ platforms.

Comet Architecture

Chromium base with AI sidebar, local processing for sensitive data, cloud for non‑sensitive tasks, contextual multi‑tab understanding.

Dia Architecture

Chromium base with AI built‑in, local encrypted storage, AI Skills system, 7‑day context memory.

Pricing and Business Models

ChatGPT Agent: tiered subscription ($20‑$200 / month) and future enterprise plans.

Comet: $200 / month Max subscription.

Fellou: per‑task pricing (0.3‑3 CNY per task).

Dia: free invitation‑only.

Market Positioning

ChatGPT Agent targets high‑end enterprise users, Comet focuses on premium search, Fellou serves business professionals with usage‑based pricing, and Dia aims at mass consumers.

Challenges and Future Trends

Reliability remains an issue with task success rates below 80% for complex operations, security concerns around prompt injection and data privacy, and high inference costs. Future directions include multimodal interaction, vertical‑specific agents, edge deployment, and evolving business models.

Conclusion

The emergence of AI‑powered web agents marks a paradigm shift from "search‑click‑browse" to "dialogue‑execute‑complete," opening new opportunities for developers and enterprises.

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