Popular:
 Building Resilient Systems on AWS: Learn how to design and implement a resilient, highly available, fault-tolerant infrastructure on AWS.

View Browser Repaints in Google Chrome and Mozilla Firefox

By  on  

One goal of super-optimized websites is to prevent browser repaints due to changes in a block's style or content. There are numerous ways we intentionally (or unintentionally) trigger block repaints, but the browser does it so quickly we have trouble seeing when and where it happens. Recognizing the importance of allowing developers to micro-optimize their pages, the Chrome and Firefox teams have added features to their browsers to allow us to see those repaints. Here's how to do it!

Google Chrome & Canary

The repaint feature needs to be enabled at startup for Chrome and Canary with the --show-paint-rects config:

open ./Google\ Chrome\ Canary.app --args --show-paint-rects

Be sure to include --args in your command or you'll run into problems opening the browser. Repaints will display on each site you visit.

Mozilla Firefox, Aurora, Nightly

To view repaints in Firefox and Aurora browsers, you need to enable an about:config option. The option name is nglayout.debug.paint_flashing. Turn this option to true and you'll quickly see repaints as the happen!

At the time of publish, only nightly exposed this config feature.

I recommend you take a few moments to scope out the repaint frequency on your websites and see what you can do to improve performance!

Request Metrics real user monitoring
Request Metrics real user monitoring
Request Metrics real user monitoring
Request Metrics real user monitoring

Recent Features

  • By
    Write Better JavaScript with Promises

    You've probably heard the talk around the water cooler about how promises are the future. All of the cool kids are using them, but you don't see what makes them so special. Can't you just use a callback? What's the big deal? In this article, we'll...

  • By
    CSS vs. JS Animation: Which is Faster?

    How is it possible that JavaScript-based animation has secretly always been as fast — or faster — than CSS transitions? And, how is it possible that Adobe and Google consistently release media-rich mobile sites that rival the performance of native apps? This article serves as a point-by-point...

Incredible Demos

  • By
    Introducing MooTools ScrollSpy

    I've been excited to release this plugin for a long time. MooTools ScrollSpy is a unique but simple MooTools plugin that listens to page scrolling and fires events based on where the user has scrolled to in the page. Now you can fire specific...

  • By
    MooTools HTML Police: dwMarkupMarine

    We've all inherited rubbish websites from webmasters that couldn't master valid HTML. You know the horrid markup: paragraph tags with align attributes and body tags with background attributes. It's almost a sin what they do. That's where dwMarkupMarine comes in.

Discussion

  1. Joe Zim

    It doesn’t look like the videos are working (in Rockmelt or Firefox)

  2. x

    Can’t see anything on Opera.

  3. Clentdc

    so what am i supposed to do with this ?
    “open ./Google\ Chrome\ Canary.app –args –show-paint-rects”

    paste it in the command line or what? im in chrome://flags, in Canary and now what?

  4. iwin

    Can’t see anything on Firefox, view repaints in Firefox and Aurora browsers

  5. dumex

    Can’t see anything Chrome.you need to enable an about

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!