UnderSurface is a diary app where inner voices respond as you write. It functions as a journaling companion that reacts to your writing in real time, creating an interactive writing experience.

The app allows you to write freely while inner voices listen and respond when you pause, trail off, or go deeper. These inner voices learn your patterns and grow with you over time, noticing what you're avoiding, sitting with you in discomfort, or connecting dots you haven't seen yet.

The product works by having you type your thoughts, and when you pause, an inner voice stirs to respond. It's designed not as a chatbot or therapist, but as a writing companion that engages with your content organically as you write.

UnderSurface helps users maintain their journaling practice by providing responsive engagement that prevents abandonment of entries when they get real. It creates a space where writing becomes a dialogue rather than a monologue.

The app works in any browser and supports multiple languages including English, Español, Français, Deutsch, Português, Italiano, Русский, 中文, 日本語, 한국어, Türkçe, Nederlands, Tiếng Việt, हिन्दी, Bahasa Indonesia, ไทย, and Polski. It includes export and account controls with strict privacy protections.