We are happy to help.
Email md@twain.md. Please include your macOS version and, for licence questions, the email address you used at purchase.
Your key is emailed to you after purchase (sent by our reseller, Paddle). In Twain, open the app menu and choose Enter Licence, then paste it. Your licence remains yours, and keeps working with no internet connection.
Lost your key? Find your licence and we will email it straight back to the address you bought with.
To preview Markdown and MDX with the spacebar in Finder, set Twain as your default Markdown app. The app has a one-click button for this. macOS shows the default app’s Quick Look preview, so this is what makes the spacebar preview use Twain.
Pro includes a 7-day trial you can start from inside the app. After the trial, Pro features prompt you to buy or enter a licence; the free viewer keeps working.