How do we know what we designed is working as intended? We measure. Vitaly Friedman shares something called the TARS framework to measure the impact of features.

We need UX metrics to understand and improve user experience. What I love most about TARS is that it’s a neat way to connect customers’ usage and customers’ experience with relevant product metrics.

Here’s TARS in a nutshell:

• Target Audience (%): Measures the percentage of all product users who have the specific problem that a feature aims to solve.
• Adoption (%): Tracks the percentage of the target audience that successfully and meaningfully engages with the feature.
• Retention (%): Assesses how many users who adopted the feature continue to use it repeatedly over time.
• Satisfaction Score (CES): Gauges the level of satisfaction, specifically how easy it was for retained users to solve their problem after using the feature.

Friedman has more details in the article, including how to use TARS to measure how well a feature is performing for your intended target audience.