Both offer system-wide AI writing on Windows. This comparison breaks down Writing Tools and WindowSill to help you decide which fits your workflow.
Writing Tools is a free, open-source application inspired by Apple Intelligence that brings system-wide AI writing assistance to Windows, Linux, and macOS. It lets you select text anywhere, press a hotkey, and instantly proofread, rewrite, adjust tone, summarize, or apply custom prompts using BYOK models like OpenAI or local LLMs. It is entirely free with no subscriptions.
WindowSill is a Windows desktop command bar that provides AI-powered text assistance (grammar fix, rewriting, translation in 35+ languages, custom prompts) alongside productivity features like media control, clipboard history, meeting management, reminders, and image utilities. WindowSill supports BYOK models like OpenAI or local LLMs. It has a free-tier. Premium features are available via a $4/month subscription or a $48 lifetime license.
| WindowSill | Writing Tools | |
|---|---|---|
| Grammar & Spelling | AI-powered proofreading via text selection with instant text replacement | AI-powered proofreading via text selection with instant text replacement |
| Tone Adjustment | Professional, casual, attention-grabbing, and custom tones presets | Friendly and Professional tone presets |
| Analysis & Rewrite | One-click summarize or rewrite | One-click summarize or rewrite |
| Translation | 35+ languages with instant translation | Via custom prompts (e.g., "translate to French") |
| Custom AI Prompts | Create reusable prompts locally with variables (date/time injection and more) | Create reusable prompts locally |
| Per-Prompt Model Selection | Choose different AI models per prompt | Not available — uses one configured model globally |
| AI Chat | Not available as a standalone feature | Built-in |
| AI Providers | 8 built-in BYOK providers, local LLMs, and any OpenAI-compatible API | Local LLMs and any OpenAI-compatible API |
| Media Control | Built-in — Spotify, YouTube, Netflix, Apple Music, and more | Not available |
| Clipboard History | With screenshot protection and password hiding | Not available |
| Meeting Control | Mute, unmute, leave Teams meetings | Not available |
| Short-Term Reminders | Full-screen (ADHD-friendly) and toast notifications | Not available |
| Image & Video Utilities | Batch convert, resize, compress | Not available |
| Extensions | SDK with growing marketplace | Not available |
| Enterprise & Organization | AI provider allow-lists, managed prompts, usage analytics | Not available |
| WindowSill | Writing Tools | |
|---|---|---|
| Price | Free tier (no AI); AI from $4/month or $48/year | Free |
| One-Time License | $48 lifetime (BYOK only) | Free |
| Enterprise | From $3.60/user/month with graduated discounts | Not available |
| AI Prompts | Unlimited | Unlimited |
| AI Cost | Included in consumer subscription, or BYOK; free with local LLMs | BYOK; free with local LLMs |
| Free Trial | 1-week free trial | No trial needed |
Start with WindowSill for free and upgrade when you need more.
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