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
    CSS Gradients

    With CSS border-radius, I showed you how CSS can bridge the gap between design and development by adding rounded corners to elements.  CSS gradients are another step in that direction.  Now that CSS gradients are supported in Internet Explorer 8+, Firefox, Safari, and Chrome...

  • By
    Creating Scrolling Parallax Effects with CSS

    Introduction For quite a long time now websites with the so called "parallax" effect have been really popular. In case you have not heard of this effect, it basically includes different layers of images that are moving in different directions or with different speed. This leads to a...

Incredible Demos

  • By
    Digg-Style Dynamic Share Widget Using MooTools

    I've always seen Digg as a very progressive website. Digg uses experimental, ajaxified methods for comments and mission-critical functions. One nice touch Digg has added to their website is their hover share widget. Here's how to implement that functionality on your site...

  • By
    Introducing MooTools LinkAlert

    One of my favorite Firefox plugins is called LinkAlert. LinkAlert shows the user an icon when they hover over a special link, like a link to a Microsoft Word DOC or a PDF file. I love that warning because I hate the surprise...

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!