case_study
Prompt Vault
Free AI prompt manager (Chrome extension)
Solo — product design, engineering, and release
- JavaScript
- Chrome MV3
- Vite
- chrome.storage.sync
problem
The problem
If you use AI every day, your best prompts scatter across old chats and notes, and every reuse costs a copy-paste round trip out of the chat and back. There was no fast, private way to keep a prompt library that lives where the work happens — inside the AI chat itself.
Doing it well meant solving two hard parts at once: inserting text reliably into composers that each use a different, frequently-changing editor (ProseMirror, Quill, Lexical), and keeping a real library — folders, templates, search — without a backend that would compromise privacy.
approach
What I engineered
- Built a Manifest V3 extension (Vanilla JS + Vite) with a popup for quick insert and a side panel for a nested-folder prompt library with drag-reorder, favorites, tags, and instant search.
- Made insertion resilient across nine AI sites by injecting via chrome.scripting with layered strategies (execCommand, paste event, native setter) and an always-on clipboard fallback, so a site changing its DOM degrades gracefully instead of breaking.
- Added a templating layer: prompts with {{variables}} ask the user to fill the blanks on insert, turning one prompt into many.
- Kept it fully serverless and private — prompts persist and sync via chrome.storage.sync with per-prompt keying to respect Chrome's sync limits, plus JSON export/import. No account, no server, no tracking.
- Shipped an in-page picker (type // in any chat), response capture, first-run onboarding, unit tests over the pure logic, and a minified, store-safe build.
result
The result
A shipped, production-ready extension that turns a scattered prompt "system" into one keystroke — insert a saved or templated prompt into any supported AI chat without leaving the conversation.
It's live and free, with a full docs site, privacy policy, and Chrome Web Store listing. The product link is below.
- 9
- supported AI chat sites
- Free
- no account · no server
- 100% local
- prompts never leave your browser
Product facts for Prompt Vault, my own free Chrome extension (2026). No usage or adoption figures are claimed.prompt-vault.sundarshahithakuri.com.np ↗
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