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Three ways to run checks in Margin.

Free checks

This instance is not offering free checks right now. Connect your own key below.

Your own key

An API key is a password that lets Margin bill AI requests to your own Claude or OpenAI account. Unlimited checks; each request costs a fraction of a cent to a few cents, so a month is usually under a dollar. A Claude.ai subscription is not an API key: API credit is bought separately, a few dollars at a time.

Choose a provider

Paste your API key

No key yet? Three steps:

  1. Sign in to the Claude Platform ↗ (or create an account there) and add a few dollars of API credit in billing.
  2. Create a key on its API keys page and copy it straight away; it is shown only once. Claude keys start with sk-ant-.
  3. Paste it above and choose Connect. Margin tests the key with Claude before saving it.

Set a monthly spending limit with your provider. Never share your key; if it leaks, delete it on the same page and create a new one.

Choose quality

Plus

Coming: hosted checks on the stronger model for a monthly price. Not available yet.

Privacy: where your key and essay go

Your key stays in this tab’s session storage until you disconnect or close the tab (browser session restore may keep it). The app server receives it with each AI request and forwards your text to the provider you chose; it never saves the key to disk. Free checks, where offered, send your text the same way on this instance’s key. Use your own copy of the app or a host you trust.

Your essays are saved to your account, so they open on any device you sign in to. Your API key is never saved to your account; it stays in this browser tab.