ScreenSage

A smart, local Chrome extension that tracks your browsing activity privately on your device and uses Chrome’s built-in AI to generate daily summaries and actionable tips

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🧠 Inspiration

We spend hours online every day — learning, working, and doom-scrolling — but rarely stop to ask how we’re spending that time. We wanted a tool that didn’t just track our activity but actually helped us grow from it — without sending a single byte to the cloud.

That’s how ScreenSage Lite was born: a privacy-first digital wellness mentor powered by Chrome’s built-in Gemini Nano AI, capable of turning your browsing habits into mindful insights and personal nudges — all locally, right on your device.

💡 What it does

ScreenSage Lite transforms your daily browsing into actionable self-reflection.

  • 🕒 Tracks your time across websites in real time — locally, not on a server.
  • 📊 Visualizes your day in an elegant dashboard with charts and streaks.
  • 🧠 Summarizes your habits using Chrome’s on-device Gemini Nano AI.
  • 💬 Provides nudges to improve focus and balance (“Try a 10-minute break before your next scroll session”).
  • ✍️ Proofreads and rewrites text with a right-click, using built-in AI APIs.
  • ☁️ Falls back seamlessly to Gemini Flash 2.5 if the local AI isn’t available.

It’s like having a calm, insightful mentor built right into your browser — one who never judges, never tracks you, and never leaks your data.

⚙️ How we built it

We built ScreenSage Lite as a Chrome Extension using the new Built-in AI APIs available in Canary (v127+).

  • Frontend: HTML, CSS, vanilla JS (modularized with ES modules)
  • UI/UX: Custom animated popup with light/dark themes, smooth parallax, and confetti feedback
  • Charts: Chart.js (locally bundled)
  • Tracking Engine: Background service worker managing tab focus, idle states, and time logs via chrome.storage.local

  • AI Logic:

    • Primary: window.ai.summarizer and window.ai.prompt (Gemini Nano)
    • Fallback: Gemini Flash 2.5 through https://generativelanguage.googleapis.com

  • Privacy Core: All data stays on the device; summaries use anonymized strings.

  • Writing Tools: Context-menu integrations for “Polish” and “Rewrite” actions inside web pages.

The result is a hybrid AI experience that feels as responsive as a local app while still having the depth of a cloud model when needed.

🧩 Challenges we ran into

  1. Stability of Built-in AI APIs — Gemini Nano is still in Early Preview, so its behavior changed between Chrome updates.
  2. Manifest V3 restrictions — The new content_security_policy rules prevented using CDNs, so we had to self-host libraries and sanitize all CSPs.
  3. Syncing popup and background data in real time without race conditions.
  4. Balancing privacy and UX — ensuring summaries were helpful without revealing identifiable data.
  5. Testing in Canary environments — every team member had slightly different AI availability statuses, making debugging... interesting 😅.

🏆 Accomplishments that we're proud of

  • Created one of the first working Chrome extensions that successfully uses both Gemini Nano and Gemini Flash 2.5 in harmony.
  • Built a fluid, animated UI that feels more like a polished desktop app than a browser extension.
  • Designed a privacy-first architecture that never sends personal data to any external server.
  • Developed AI-powered writing tools that run entirely inside the browser context — no backend, no latency.
  • Achieved stable local tracking and AI summaries without performance degradation.

📚 What we learned

  • Chrome’s new AI stack is incredibly capable. Gemini Nano is fast, lightweight, and surprisingly fluent.
  • Privacy and intelligence can coexist. On-device AI opens a new paradigm for personal software — one where users remain in control.
  • CSP and Manifest v3 can be strict, but they push you toward safer, cleaner extension design.
  • Hybrid AI strategies (local + cloud) are the future — not everything needs a massive server backend.

🚀 What’s next for ScreenSage

  • 🖼️ Multimodal Gemini Nano — integrate vision and audio summarization (e.g., summarize YouTube watch history visually).
  • 🧘 Mindful notifications — gentle, AI-generated reminders to rest or focus when patterns suggest burnout.
  • 📱 Cross-device sync using encrypted Chrome Storage.
  • 🔒 Advanced privacy controls — user-defined retention policies and per-domain exclusions.
  • 🌙 Mood-adaptive themes — interface subtly shifts tone based on time of day and browsing behavior.
  • 🧩 Public release on Chrome Web Store after Gemini Nano exits preview.

ScreenSage Lite started as a hackathon idea — but we believe it can become a foundation for a new category of local-first, self-aware productivity tools.

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