A Primer on Performance

  • The Lead Developer 2015
  • Una Kravets | @una

Make something people love

people don't hate



an action, task, or operation, seen in terms of how successfully it was performed

Performance is Our Biggest Job

Beautiful != Useable

Useable > Beautiful

Performance-First Design

Google has calculated that by slowing its search results by just four tenths of a second they could lose 8 million searches per day.

  • 8 million searches
  • $111,000/day
  • $40.5 million/year

100% of users have felt frustated by poor performance. - Una Kravets

Facepalm gif

It's about Neuroscience

Web Stress

Sensory Memory

UX Architecture

Content Strategy

Do I really need that?

What Is the Main Goal Here?

What Next?

UI Design

lego cake!

Image File Types

  • jpg

  • png-8

  • png-24

  • gif

  • svg

"Never put an image on the web that you haven't optimized"
- Dave Rupert

Compression Tools

Compressive Images

size: 109kb

size: 49kb

size: 109kb

size: 49kb

Progressive .JPEGs

It's About How Fast the Page Feels

Retina Images

Do I really need that?


  • Picturefill
  • whatdoesmysitecost.com


    60 FPS

    Timeline Panel

    Dev Tips Daily

  • csstriggers.com
  • High Performance Animations
  • Flexbox > Older Layout Models

    Use Flexbox
  • Stolen from Paul Lewis
  • Use Flexbox


    Style Audit


  • Harry Roberts
  • Front End Development

    Cupcake Truck

    The Delivery


    • Concatenate
    • Minify
    • Async
    • Test

    C: Concatenate

    Pull your files into one to minimize requests.

  • Images

  • CSS

    @import 'vendors/bootstrap';
    @import 'vendors/jquery-ui';
    @import 'utils/variables';
    @import 'utils/functions';
    @import 'utils/mixins';
    @import 'utils/placeholders';
    @import 'base/reset';
    @import 'base/typography';
    @import 'layout/navigation';
    @import 'layout/grid';
    @import 'layout/header';
    @import 'layout/footer';
    @import 'layout/sidebar';
    @import 'layout/forms';
    @import 'components/buttons';
    @import 'components/carousel';
    @import 'components/cover';
    @import 'components/dropdown';
    @import 'pages/home';
    @import 'pages/contact';
    @import 'themes/theme';
    @import 'themes/admin';
  • Javascript

    var concat = require('gulp-concat');
    gulp.task('scripts', function() {
      gulp.src(['./lib/file3.js', './lib/file1.js', './lib/file2.js'])
  • The fastest HTTP request is the one not made.
    -Steve Souders, Head Performance Engineer, Google

    M: Minify

    Make those files as small as possible.

  • Images

  • CSS

    body,fieldset,form,html,legend,li,ol,ul{margin:0;padding:0}h1,h2,h3,h4,h5,h6,p{margin-top:0}fieldset,img{border:0}legend{color:#000}li{list-style:none}sup{vertical-align:text-top}sub{vertical-align:text-bottom}table{border-collapse:collapse;border-spacing:0}caption,td,th{text-align:left;vertical-align:top;font-weight:400}input,select,textarea{font-size:110%;line-height:1.1}abbr,acronym{border-bottom:.1em dotted;cursor:help}*,:after,:before{margin:0;padding:0;-moz-box-sizing:border-box;-webkit-box-sizing:border-box;box-sizing:border-box}html{-webkit-font-smoothing:antialiased;height:100%}body{font-family:"Carrois Gothic",sans-serif;font-weight:400;padding:2em 10% 4em;max-width:1000px;margin:0 auto;background:#eef0f0;min-height:100%;position:relative}h1,h2,h3{font-family:"Fjalla One",serif;font-weight:700}h1{font-size:3.5em;margin-bottom:.25em;color:#5ab1bb}h2{color:#4e6766;font-family:"Carrois Gothic",sans-serif;text-transform:uppercase;font-size:.9em;letter-spacing:2px}
  • Javascript

    !function(a,b){"object"==typeof module&&"object"==typeof module.exports?module.exports=a.document?b(a,!0):function(a){if(!a.document)throw new Error("jQuery requires a window with a document");return b(a)}:b(a)}("undefined"!=typeof window?window:this,function(a,b){var c=[],d=c.slice,e=c.concat,f=c.push,g=c.indexOf,h={},i=h.toString,j=h.hasOwnProperty,k={},l="1.11.2",m=function(a,b){return new m.fn.init(a,b)},n=/^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g,o=/^-ms-/,p=/-([\da-z])/gi,q=function(a,b){return b.toUpperCase()};m.fn=m.prototype={jquery:l,constructor:m,selector:"",length:0,toArray:function(){return d.call(this)},get:function(a){return null!=a?0>a?this[a+this.length]:this[a]:d.call(this)},pushStack:function(a){var b=m.merge(this.constructor(),a);return b.prevObject=this,b.context=this.context,b},each:function(a,b){return m.each(this,a,b)},map:function(a){return this.pushStack(m.map(this,function(b,c){return a.call(b,c,b)}))},slice:function(){return this.pushStack(d.apply(this,arguments))},first:function(){return this.eq(0)},last:function(){return this.eq(-1)},eq:function(a){var b=this.length,c=+a+(0>a?b:0);return this.pushStack(c>=0&&b>c?[this[c]]:[])},end:function(){return this.
  • Optimize what people see immediately

    • Scripts
    • Styles

    critical rendering path:

    /[krit-i-kuh l] [ren-der-ing] [path, pahth]/

    The intermediate steps between receiving the HTML, CSS, and JavaScript bytes and the required processing to turn them into rendered pixels

    A: Async

    Manage How Your Scripts load with Async & Defer.

    • <script src="...">

    • <script src="..." async>

    • <script src="..." defer>


    < head>
    < /head>

    Critical CSS

    "We don’t need to render the entire page in one second, [just] the above the fold content."
    - Ilya Grigorik

    T: Test

    Check Your Performance

    Render. Display. Interact.

    Chrome Dev Tools

    Network Panel

    Audits Panel


    page speed index:

    /[peyj] [speed] [in-deks]/

    some hippie math that tells you how fast it "feels" to load your website.

    Google PageSpeed Insights

    Page Speed Insights Extension

    Google Analytics

    Automate Your Performance Testing

    Javascript Task Runners

    Using Gulp

    var gulp = require('gulp');
    var psi = require('psi');
    var site = 'http://www.html5rocks.com';
    var key = '';
    gulp.task('mobile', function () {
        return psi(site, {
            // key: key
            nokey: 'true',
            strategy: 'mobile',
        }, function (err, data) {
    gulp.task('desktop', function () {
        return psi(site, {
            nokey: 'true',
            // key: key,
            strategy: 'desktop',
        }, function (err, data) {
    gulp.task('default', ['mobile']);


    URL:       https://www.google.com/?gws_rd=ssl
    Score:     92
    Strategy:  desktop
    Number Resources                           | 13
    Number Hosts                               | 5
    Total Request                              | 2.62 kB
    Number Static Resources                    | 9
    Html Response                              | 116.9 kB
    Image Response                             | 46.02 kB
    Javascript Response                        | 879.68 kB
    Other Response                             | 1.76 kB
    Number Js Resources                        | 5
    Avoid Landing Page Redirects               | 7
    Enable Gzip Compression                    | 0
    Leverage Browser Caching                   | 0
    Main Resource Server Response Time         | 0
    Minify Css                                 | 0
    Minify HTML                                | 0
    Minify Java Script                         | 0.27
    Minimize Render Blocking Resources         | 0
    Optimize Images                            | 0
    Prioritize Visible Content                 | 0

    Performance Budget

    Let's Review

    We're All in This Together

    Performance Optimization Checklist:

    • Determine Important Content
    • Create Most Performant Images
    • Optimize Images
    • DRY Stylesheet Architecture
    • Consider Critical Rendering Path
    • Concatenate files
    • Minify files
    • Async/Defer script loading
    • Test! Repeat! Iterate!

    Thank You!