It lays out the picture and helps you know what type of testing will be appropriate for your application.
Software testers perform it to ensure visual consistency and prevent regressions caused by changes in code or design.
Choose a test execution tool that can filter out false positives and handle errors like anti-aliasing, pixel offsets, etc.
Test automation should be used for dynamic and moving content.
Don't rely on error ratios or thresholds. What matters is visible changes and how it impacts users.
Automation algorithms should be capable of assessing page structure and comparing layouts.
Instead of validating individual components, validate the entire UI page. It will result in increased coverage.