Terralog is a mobile application that functions as a personal logbook for outings such as trips, walks, visits, and weekends. The application is designed to store all data directly on the user's device. Users begin by setting a departure point and then add stages to their journey. The app calculates routes, distances, and durations using a public mapping service, with the caveat that these are estimates rather than guarantees. It also flags when a day's itinerary appears unrealistic. At each stage, users can attach text, photos, audio recordings, or videos. The application emphasizes privacy and data control. No account registration, password, or email address is required; instead, users choose a name or pseudonym, a code, and a phrase. The device stores only fingerprints of this information. Data remains on the phone unless the user explicitly chooses to share it, and shared content is encrypted with the user holding the decryption key. The app includes no trackers, advertising networks, or third-party services. The developer states that server-stored data is unreadable, including to the application's author. Terralog supports offline functionality through downloadable regional maps. Users can add stages via GPS without a network connection, though searching for locations by name requires connectivity. The application is free during its beta period and is available in nineteen languages. It is developed by a single individual without investors or external funding. The app includes an in-app guided tour that demonstrates its features through voice narration and interactive prompts.