WindowSill - Free AI Command Bar for Windows

TL;DR

TL;DR: WindowSill is a free Windows command bar that brings AI writing assistance — grammar check, tone rewriting, and translation — directly into any app via a global hotkey. It also ships clipboard history, media controls, and reminders out of the box.

What Is WindowSill?

WindowSill is a Windows-native productivity bar that lives in the system tray and springs to life via a global hotkey. Unlike browser extensions that only work inside web apps, WindowSill intercepts selected text system-wide and runs it through AI-powered tools regardless of which application you’re in.

The core pitch: you select text anywhere, press Alt+Space, and get instant access to grammar correction, tone adjustment, text rewriting, and translation across 35+ languages — without switching windows or copy-pasting into a separate tool.

It sits in the background consuming minimal RAM and stays out of your way until you need it.

Features

From the official product page:

• AI writing assistant — grammar and spell check on selected text
• Text rewriter — adjust tone (formal, casual, professional, etc.)
• AI translation — 35+ languages, works in any app
• Custom AI prompts — define your own rewriting/transformation rules
• Clipboard history — searchable history of recent copies
• Media controls — system-wide playback control (Spotify, YouTube, etc.)
• Short-term reminders — set quick in-app reminders
• Unit converter — built-in quick conversions
• Web browser control — play/pause/forward/rewind any web media
• App launcher — launch apps and URLs from the command bar
• Customizable extensions — community-made extensions available

The free tier includes all core productivity features. WindowSill+ ($4/month) unlocks AI writing assistance (grammar, rewriting, tone, translation). WindowSill Pro adds organization-wide management, graduated pricing for teams, and BYOK (bring your own key) for OpenAI, Anthropic, Google, and local LLMs.

Setup

Install

Download from the Microsoft Store:

# Search "WindowSill" in the Microsoft Store app
# Or visit directly:
https://apps.microsoft.com/detail/9PG6CJPXTPZ0
```bash

No install wizard — it lands in your Start menu and system tray automatically.

### First Launch

1. Open WindowSill from the Start menu
2. It will request **Accessibility** permission (required to read selected text globally)
3. The icon appears in the system tray
4. Press `Alt+Space` to open the command bar

### Enable AI Features

1. Click the system tray icon → **Dashboard**
2. Under **WindowSill+**, click **Start Free Trial** (7-day trial)
3. Or go to **Settings → AI** and add your own API key (Pro only)

## How It Works

WindowSill registers a global hotkey (`Alt+Space` by default) that opens a floating overlay. The overlay reads the currently selected text via Windows Accessibility APIs, sends it to the AI backend (or your own API key), and returns the result to a side panel — all without switching focus from your active app.

```text
User selects text in any app
        ↓
Alt+Space opens WindowSill overlay
        ↓
Selected text sent to AI (or your own API)
        ↓
Result shown in side panel → click to copy/replace

This design means it works inside VS Code, Slack, Notion, Gmail, or any other Windows application — no per-app extension needed.

Practical Evaluation Checklist

• ✅ Works in any Windows app via Accessibility API
• ✅ Grammar and spell check with one keystroke
• ✅ Tone rewriting (formal, casual, professional, friendly)
• ✅ 35+ language translation
• ✅ Clipboard history with search
• ✅ Media controls for web and desktop players
• ✅ Custom AI prompts (define your own rewrite rules)
• ✅ Free tier covers all non-AI features
• ⚠️ AI features require WindowSill+ ($4/month) or Pro
• ⚠️ Requires Windows 10/11 with Accessibility permission

Security Notes

WindowSill needs Accessibility permission to read selected text. This is a broad permission — review the privacy policy before enabling on a work machine. The Pro tier’s BYOK option lets you route AI requests through your own API keys, avoiding WindowSill’s servers entirely for AI processing.

FAQ

Q: Is WindowSill free? A: Yes, the core productivity features (clipboard history, media controls, reminders, unit converter, app launcher) are free forever. AI writing assistance requires WindowSill+ ($4/month) after a 7-day free trial.

Q: Does it work with my own API key? A: WindowSill Pro supports BYOK for OpenAI, Anthropic, Google, and local LLMs. This keeps AI text off WindowSill’s servers.

Q: How is it different from PowerToys Run? A: PowerToys Run is a file/app launcher with plugin support. WindowSill is focused on text manipulation — selecting text and running AI operations on it. They coexist fine.

Q: Does it work on Linux or macOS? A: No — WindowSill is Windows-only, using Windows Accessibility APIs.

Source and Accuracy Notes

• Project page: getwindowsill.app
• Microsoft Store listing: apps.microsoft.com/detail/9PG6CJPXTPZ0
• GitHub organization: github.com/WindowSill-app (no public repo as of publish)
• HN launch thread: news.ycombinator.com/item?id=45346593
• License: Proprietary (not open source)