Diary with lock is a free iPhone app developed by Tuyen Bui. It falls under the lifestyle category and provides users with a secure and personalized way to keep a journal of daily events, appointments, secrets, and feelings. With password and pin code protection, your entries will remain private and secure.

The app offers several features to enhance your journaling experience. You can personalize the background color with options like pink, purple, and blue. Additionally, you can change the font style to suit your preference. The user interface is designed to be easy to use, allowing you to quickly enter new notes. You can also search for specific entries and make unlimited entries in your diary.

One standout feature of Diary with lock is its support for three languages: English, Japanese, and Vietnamese. This makes it accessible to a wider range of users. It's worth noting that Diary with lock is the most downloaded diary app on the AppStore, which speaks to its popularity and reliability.