Leak Detector reads the hidden marks in copies made by File Watermarker, ARC Tracker and Reader Magnets, and tells you who a copy was made for.

## Check a file

1. Download the pirated file to your computer.
2. Open **Leak Detector** from the sidebar.
3. Make sure the **Upload a file** tab is selected.
4. Drag the file onto the page, or click **Choose a file** and pick it.

The check starts as soon as you add the file. While it runs you'll see **Reading the marks…**. The file is read in your browser and isn't uploaded anywhere.

You can drop the file anywhere on the Leak Detector page, not only on the box. On other pages of the app, dropping a PDF or EPUB offers a choice of tools; pick **Leak Detector** to check it there.

## What files work

- PDF and EPUB files up to 50 MB.
- A plain text (.txt) file dropped on the page is moved into the **Paste some text** tab and checked as text.

For anything else, copy some text out of it and paste it instead.

## Reading the result

A match says **This looks like the copy made for** the reader, then lists their **Email**, the **Book** (or **Reader magnet**), when the copy was **Made**, and what was **Found**: a hidden ID in the file's properties, hidden text in the file, or invisible characters in the book's own text.

To check another file, click **Check a different file**. A file you've already checked shows its earlier result straight away.

A match shows whose copy it was, not who shared it. A copy can be passed on by someone else, so use it to start a conversation rather than to accuse anyone.