TTFB (Time to First Behavior)

Time to First Behavior (TTFB) is the elapsed time between a user’s first exposure to a solution and their first completion of the target behavior. It measures how quickly the solution enables the validated behavior.

Key Insight

Shorter TTFB correlates with higher retention. When users perform the target behavior quickly, they experience value sooner, reinforcing continued engagement. Long TTFB often signals friction or misalignment between the solution and the behavior.

Measurement

TTFB = timestamp(first_behavior_completion) - timestamp(first_exposure)

First exposure is typically defined as:

• App install or first open
• Account creation
• Landing page arrival
• Onboarding start

First behavior completion is the validated target behavior, not a proxy action.

Examples

Why TTFB Matters

1. Validates Solution Fit: If TTFB is long, the solution may not be enabling the behavior effectively
2. Predicts Retention: Users who complete the target behavior quickly are more likely to return
3. Identifies Friction: High median TTFB reveals onboarding or UX barriers
4. Segments Users: TTFB distribution can identify distinct user segments with different needs

Optimization Strategies

• Remove friction: Reduce steps between exposure and behavior
• Progressive disclosure: Show only what’s needed to perform the first behavior
• Default to action: Pre-populate or pre-select to enable faster completion
• Immediate feedback: Reward the first behavior to reinforce continuation

Relationship to Other Metrics