Plainer — F.A.Q.

What is Plainer? Plainer is a free Chrome extension that explains anything you read on the web. Highlight a word, phrase, or sentence, click the Plainer button that appears, and get a clear plain-English explanation powered by Claude AI — without leaving the page.

Does Plainer work on every website? Yes. Plainer runs on any webpage you visit in Chrome, including news sites, Wikipedia, research papers, documentation, and social media.

Is Plainer free? Plainer itself is free. You do need your own Anthropic API key to use it, and Anthropic charge a small fee per request — but Claude Haiku (the model Plainer uses) is one of the cheapest AI models available. Light daily use typically costs pennies a month.

What is an Anthropic API key and where do I get one? It's a personal key that lets Plainer talk to Claude on your behalf. You can get one at console.anthropic.com — you'll need to create a free account and add a small amount of credit to get started.

Is my API key safe? Yes. Your key is stored locally in your browser and is only ever sent directly to Anthropic's API — never to any server run by Plainer or cmdzed.com. The key is handled exclusively inside the extension's background worker, so it never appears in any message that could be intercepted by other extensions.

Does Plainer collect my data? No. Plainer's developer never sees your key, your queries, or the text you highlight. When you use Plainer, your selected text and some page context are sent directly from your browser to Anthropic's API under your own key. You can read the full Privacy Policy for details.

How do I install Plainer? Download the extension from the Chrome Web Store, click Add to Chrome, then click the Plainer icon in your toolbar to open Settings and enter your API key.

How do I use it? Select any text on a webpage, wait a moment, and a small Plainer button will appear near your selection. Click it to get an explanation. You can then tap any of the follow-up questions to go deeper.

Why isn't the Plainer button appearing? Make sure you've selected at least 3 characters of text. The button won't appear if you click somewhere else before it has a chance to show. If it never appears, try reloading the page — occasionally a page update requires a refresh to activate the extension.

Why am I seeing "No API key set"? You haven't entered your Anthropic API key yet. Click the Plainer icon in your Chrome toolbar to open Settings, paste your key into the API Key field, and click Save Settings.

My API key isn't working — what do I do? Open Settings and use the Test Connection button to check your key. Common causes are: a typo when pasting, the key having been revoked in the Anthropic console, or your Anthropic account having no credit remaining.

Can I customise how Plainer explains things? Yes. In Settings you can enter your name, your role (e.g. "UX Designer"), and custom instructions (e.g. "always use real-world examples" or "keep it under two sentences"). Plainer uses this to tailor every explanation to your background.

What is the "Continue with Claude" button? It's the small arrow icon in the top-right of the popover. Clicking it opens Claude.ai in a new tab with the explanation pre-loaded, so you can continue the conversation with the full Claude interface.

How do the follow-up questions work? After each explanation, Plainer suggests three natural follow-up questions. Clicking one sends it back to Claude with the original context, so the answers stay grounded in what you were reading — not just the term in isolation.

Does Plainer work on PDFs in the browser? It works on PDFs opened directly in Chrome's built-in PDF viewer, as long as the text is selectable (scanned PDFs where the text is an image won't work).

What happens if the explanation is wrong? Claude is very good but not infallible. Treat explanations as a helpful starting point rather than a definitive source, especially for technical, legal, or medical content. The "Continue with Claude" button is a good way to probe further or fact-check.

Can I change the colour of the Plainer button and popover? Yes — open Settings and choose from six accent colours: green, blue, red, amber, pink, and purple.

Will Plainer slow down my browsing? No. The extension only activates when you highlight text and click the button. It makes no background requests, runs no background processes between uses, and loads after each page is fully rendered.

Does Plainer work in other browsers like Firefox or Safari? Not currently. Plainer is built for Chrome (and Chromium-based browsers like Edge and Brave). Firefox and Safari support may come in a future version.

Where can I report a bug or suggest a feature? Head to cmdzed.com and get in touch — feedback is always welcome and directly shapes what gets built next.