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
    Send Text Messages with PHP

    Kids these days, I tell ya.  All they care about is the technology.  The video games.  The bottled water.  Oh, and the texting, always the texting.  Back in my day, all we had was...OK, I had all of these things too.  But I still don't get...

  • By
    JavaScript Promise API

    While synchronous code is easier to follow and debug, async is generally better for performance and flexibility. Why "hold up the show" when you can trigger numerous requests at once and then handle them when each is ready?  Promises are becoming a big part of the JavaScript world...

Incredible Demos

  • By
    Save Web Form Content Using Control + S

    We've all used word processing applications like Microsoft Word and if there's one thing they've taught you it's that you need to save every few seconds in anticipation of the inevitable crash. WordPress has mimicked this functionality within their WYSIWYG editor and I use it...

  • By
    MooTools Star Ratings with MooStarRating

    I've said it over and over but I'll say it again:  JavaScript's main role in web applications is to enhance otherwise boring, static functionality provided by the browser.  One perfect example of this is the Javascript/AJAX-powered star rating systems that have become popular over the...

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!