Lighthouse – Google Site Evaluation Tool

Lighthouse is an open-source, automated tool for improving the performance, quality, and correctness of your web apps.

When auditing a page, Lighthouse runs a barrage of tests against the page, and then generates a report on how well the page did. From here you can use the failing tests as indicators on what you can do to improve your app.

Get it at Chrome Web Store
Or check out it’s home page

Here’s some feedback from Lighthouse on this here site:
LightHouseReview

LightHouseReview2

LightHouseReview3