Use OpenRouter in Chrome, in any text field

What you get

OpenRouter gives you one account and one key for models from many companies. ShroomPen puts those models on every web page. You click into the field you are writing in, open ShroomPen over the page, ask for a reply, a rewrite or a translation, and the draft goes back into that field when you click Insert draft.

You choose the context for each request: the page, the field you are in, the text you selected, other open tabs (PDF tabs too) or a saved Workspace. Password, one-time code and payment fields are left out. You can open the exact request before it is sent, with the key hidden.

Connect OpenRouter

1. Install ShroomPen and enable it

   Add ShroomPen from the Chrome Web Store. The first time you open it, it explains what it can read and waits until you tick the box and click Enable ShroomPen.

   Add ShroomPen to Chrome. It is free and needs no ShroomPen account.

2. Choose OpenRouter

   Open ShroomPen with Ctrl+Q. On first run choose OpenRouter in the setup; later, open settings, choose Add provider, then OpenRouter.

3. Sign in with OpenRouter

   Click Continue with OpenRouter. A window opens on openrouter.ai where you sign in, or create an account, and approve the connection. The window closes and ShroomPen says OpenRouter is connected.

4. Pick a model

   ShroomPen starts on openrouter/free. Pick another model from the Recommended list or from All OpenRouter models, where free models are marked Free.

5. Write in a text field

   Click into any text field on a page, press Ctrl+Q, type what you want, read the draft and click Insert draft. ShroomPen never changes a field on its own.

How the one-click sign-in works

ShroomPen uses OpenRouter’s OAuth PKCE flow, which is built for apps like this one that have no server:

1. The extension makes a one-time secret, keeps it in Chrome’s session storage, and sends only its SHA-256 hash to openrouter.ai/auth.
2. You sign in on openrouter.ai and approve. OpenRouter sends a short-lived code back to the extension.
3. The extension sends the code and the secret to OpenRouter, which checks them against the hash and returns an API key tied to your account.
4. The key is saved in the extension’s local storage. The one-time secret is deleted.

No password or key passes through a ShroomPen server, because there isn’t one. The key is yours: you can see your usage on OpenRouter and remove the key there or with Disconnect in ShroomPen.

What it costs

ShroomPen is free. You pay OpenRouter for what you use, and OpenRouter passes model prices through without a markup. Buying credits by card carries a 5.5% fee, with a $0.80 minimum.

Prices are from OpenRouter’s model list in September 2026 and change often. A typical email reply is a few thousand tokens in and a few hundred out, so on the cheaper paid models it costs a fraction of a cent.

Privacy

The request, including any page text you chose to attach, goes from your browser to OpenRouter, which forwards it to the company that runs the model. OpenRouter says it does not log prompts or completions unless you opt in. The model providers have their own policies, and some free models may use your data for training. In OpenRouter’s privacy settings you can turn off routing to providers that may train on your data.

ShroomPen’s requests tell OpenRouter which app they come from (the ShroomPen name and website address), which is how OpenRouter credits usage to an app. They carry nothing else about you. For text that should never leave your computer, use a local model: see Use Ollama in Chrome.

ShroomPen or something else?

Other ways to use OpenRouter models in the browser are better in some cases:

• OpenRouter’s own Chatroom needs no install and is the better place to compare several models side by side. You copy the answer into your page yourself.
• Page Assist is an open-source sidebar chat that supports OpenRouter and many other providers, and it runs in Firefox too. You add OpenRouter by pasting an API key.
• ShroomPen is for writing on the page: the draft goes into the field you are working in, and OpenRouter connects with one sign-in instead of a pasted key. It is closed source and Chrome-only.

Related

• Use Ollama in Chrome: a free local model instead of a hosted one
• Privacy policy: what ShroomPen handles and stores