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
    Serving Fonts from CDN

    For maximum performance, we all know we must put our assets on CDN (another domain).  Along with those assets are custom web fonts.  Unfortunately custom web fonts via CDN (or any cross-domain font request) don't work in Firefox or Internet Explorer (correctly so, by spec) though...

  • By
    Convert XML to JSON with JavaScript

    If you follow me on Twitter, you know that I've been working on a super top secret mobile application using Appcelerator Titanium.  The experience has been great:  using JavaScript to create easy to write, easy to test, native mobile apps has been fun.  My...

Incredible Demos

  • By
    Dynamic Waveform Visualizations with wavesurfer.js

    Waveform images are an awesome addition to boring audio widgets.  They can be functional as well as aesthetically pleasing, allowing users to navigate audio visually.  I recently found wavesurfer.js, an amazing waveform image utility that uses to Web Audio API to create super customizable...

  • By
    CSS Rounded Corners

    The ability to create rounded corners with CSS opens the possibility of subtle design improvements without the need to include images.  CSS rounded corners thus save us time in creating images and requests to the server.  Today, rounded corners with CSS are supported by all of...

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!