1. Go to Instagram Settings → Security → Download Data
2. Request a download of your data
3. Once received, extract the ZIP file
4. Open the following.html and followers.html files
5. Copy everything and paste here - dates and URLs will be automatically removed!

You can also manually copy usernames from your Instagram app:

1. Go to your profile
2. Tap on "Following" or "Followers"
3. Copy usernames one by one
4. Paste them into the respective field (one per line)

Your data is completely safe!

✓ All comparisons happen locally in your browser
✓ No data is sent to any server
✓ No login required
✓ No data is stored or tracked

This tool is 100% client-side and open source.