Capture instantly.
Write without structure, folders, or friction.
Underline Labs
Think freely. Find the signal.
Underline is a private thinking system for capturing ideas, underlining what matters, and connecting your thoughts into something meaningful.
Your thoughts are scattered.
Notes pile up. Ideas repeat. Search only gets you halfway. Underline helps you turn messy thinking into connected clarity.
A calmer product loop.
Underline what matters.
Highlight promising thoughts and turn them into signals.
Connect your ideas.
Map relationships between notes, questions, and insights.
Rediscover what matters.
Search across notes, signals, topics, and meaning.
Everything points back to the signal.
Instant capture
Open the app and start writing immediately.
Signals
Underline the phrases that feel important. Underline remembers them.
AI-assisted organization
Get optional suggestions for tags, topics, summaries, and related ideas.
Visual canvas
Turn thoughts into maps and connect ideas with arrows.
Powerful search
Find notes, signals, topics, and the threads between them.
Private-first
Your thinking space should feel safe, quiet, and yours.
Built for thinking, not filing.
Underline does not force folders, rigid structures, or over-organization. It gives you a fast place to think, then helps you gently organize only when a thought starts to matter.
Designed to feel safe.
Private-first
Secure authentication
Encrypted connections
User-controlled AI
Accessibility-first