Plainer — Privacy Policy

Last updated: March 2026

Plainer is a free browser extension built by Fearghal Hendron (cmdzed.com). This privacy policy explains clearly and honestly what data Plainer accesses, what it sends, and what it stores.

The short version

Plainer sends your highlighted text and some page metadata to Anthropic's Claude API to generate an explanation. It uses your own Anthropic API key to do this — Fearghal never sees your key, your text, or your queries.

What data does Plainer collect?

Plainer does not collect, store, or transmit any data to its developer. When you highlight text and click the Plainer button, the following information is sent directly from your browser to Anthropic's API (api.anthropic.com) to generate an explanation:

  • The text you highlighted
  • The URL of the page you are reading
  • The page title, heading, description, and a short excerpt of surrounding text (for context)
  • Your name and role (if you have set these in Settings)
  • Your custom instructions (if you have set these in Settings)

This data is processed by Anthropic under Anthropic's Privacy Policy. Plainer's developer receives none of it.

What does Plainer store locally?

Plainer stores the following in your browser's synced storage (chrome.storage.sync), which is managed by your browser account (e.g. Google Chrome sync):

  • Your Anthropic API key
  • Your name and role (optional)
  • Your custom instructions (optional)
  • Your chosen theme colour
  • Whether debug mode is enabled

Because chrome.storage.sync is used, these settings are synced across your Chrome profile's devices via Google's infrastructure. If you prefer to keep settings device-local only, you can use a separate browser profile.

Your API key

You provide your own Anthropic API key. Plainer reads it directly from browser storage within the extension's background worker and uses it solely to make requests to Anthropic's API on your behalf. The key is never sent to any server operated by Plainer's developer, and never included in any analytics or logging.

Does Plainer use analytics, advertising, or third-party tracking?

No. Plainer contains no analytics, no advertising, no tracking pixels, and no third-party SDKs. The extension makes no external requests of any kind other than to Anthropic's API when you request an explanation.

Who receives your data?

Only Anthropic. When you use Plainer, your highlighted text and page context are sent to https://api.anthropic.com under your own API key. Anthropic's data handling is governed by their Privacy Policy and Usage Policy.

How can I delete my data?

To remove all locally stored data, uninstall the Plainer extension from your browser. This clears all settings from chrome.storage.sync. Any data already sent to Anthropic is subject to their data retention policies.

Changes to this policy

If this policy changes materially, the updated version will be published at this URL with a new "Last updated" date.

Contact

Questions? Reach out via cmdzed.com.