Margin

Margin reads your essay the way your professor will.

A grade estimate, the three fixes that matter most, and the exact lines to change. It never writes your essay for you. Free to try; plug in your own AI key for unlimited.

Try it on a sampleSign in

The creature is not innocent either. After the De Lacey family rejects him he decides to take revenge on all of humanity, and especially on Victor. He murders William, frames Justine, and later kills Clerval and Elizabeth. He even tells Victor, "Beware; for I am fearless, and therefore powerful" (Shelley ch. 20). At this point in the novel the creature has stopped asking for sympathy, he is making threats. Society has always rejected what it does not understand, so it is not surprising that the creature turned violent. His crimes effected everyone around Victor, which proves that the creature had become a monster.

Grammar

Two complete sentences joined by a comma. A semicolon after 'sympathy' keeps the turn from pleading to threatening in one line.

the creature has stopped asking for sympathy, he is making threats the creature has stopped asking for sympathy; he is making threats

Paragraph three of the sample essay, as checked. The whole draft grades C (75%). See the full result.

Grades like your rubric

Six traits, weighted the way an English rubric weights them: evidence counts three times as much as mechanics. You get a letter, a percent, the level on each trait, and the three changes that would raise it most.

Fixes, not rewrites

Each note names the words and the change. A comma or a wrong word gets the exact replacement. A thin argument gets what to add, in your own words, not a paragraph written for you.

Real quotes only

Every line it points at is in your draft, and every quotation it suggests comes from a source you uploaded. If it cannot find it, it does not show it.

Is this allowed?

Margin marks problems and shows you how to fix them in your own words. It will not draft paragraphs, pad your argument, or invent quotations: every quotation it suggests comes from a source you uploaded. Treat it like a writing center: it reads and points, you write. If your course asks about AI use, say you used it to check your draft.

Pricing

Free
A monthly allowance of checks on every account, when this instance offers them; a copy you host yourself runs on your own key.
Your own key
Unlimited. Your provider bills you, usually under a dollar a month.
Plus
Coming.

Try it on a sample

AI settings

Not connected

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.