Splain is a tiny desktop widget that lives on your screen, one click away. Select any word anywhere on your computer, paste it in, and get a clear explanation in plain language — in whatever language you choose. It's also a full AI chat assistant for quick questions, brainstorming, and thinking things through.What it does- 📖 Explain any word in simple, 2–3 sentence language. Pick the output language (auto, English, Dutch, French, German, Spanish, Italian, Portuguese).- 💬 AI assistant that mirrors your language, remembers your name, and follows your custom persona/instructions.- ⚡ Instant repeats — explained words are cached locally, so asking again is free and works offline.- 🎛️ Choose your provider: OpenAI, Anthropic (Claude), or Google Gemini — including Gemini's free tier.- 🎨 Adjustable text size, dark theme, lock the widget anywhere on your desktop.Private by design- Bring your own API key. It's stored in the Windows Credential Vault — never on disk, never sent to us.- No account, no tracking, no data collection. Your words and chats stay on your machine.What does it cost to run?Splain is free. You use your own API key and pay the AI provider directly for what you use — nothing goes to us, no markup, no subscription. Typical cost with the default model (GPT‑4o‑mini) is about half a hundredth of a cent per message. Prefer zero cost? Pick Google Gemini and normal use stays within its free tier.Windows • one file • no installer.