Promptin

Promptin is a slash-command prompt manager that lives inside the chat box of ChatGPT, Claude, Gemini and Grok. Type a slash command and your saved prompt is injected straight into the composer — no copy-paste, no switching tabs to a note somewhere.

It has grown to 200+ weekly users.

Staying out of the host page's way#

The hard part of a browser extension that injects UI into someone else's app is that you do not control their markup, and it changes without warning. Promptin renders its UI inside a Shadow DOM so its styles never leak into — or get broken by — the host page, and uses a MutationObserver to re-attach itself whenever the underlying chat interface re-renders.

That combination is what lets one extension support four different AI products that each structure their DOM differently, without a per-site rewrite every time one of them ships a redesign.

It holds a 5/5 rating on the Chrome Web Store. More at prompt-in.com, and the code is on GitHub.