understanding ux & hacking perceived performance
TRANSCRIPT
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Understanding UX & Hacking Perceived Performance
NY Web Performance Meetup • May 2016
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@tamevertsperformancebeacon.com
WPOstats.com
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Source: 1&1 Internet
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The average web user believes they waste two days a year
waiting for pages to load.
Source: 1&1 Internet
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Source: Akamai
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Source: Stoyan Stefanov, The Psychology of Speed
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Source: webperf.io
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“The real thing we are after is to create a user experience
that people love and they feel is fast… and so we might be
front-end engineers, we might be dev,
we might be ops, but what we really are is perception
brokers.”
Steve Souders
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“Oh… pity the hyper-impatient web generation. Such busy lives with so many important things to
do — like post the latest drivel onto their Facebook pages or
download the YouTube viral video of the day.
Oops, sorry — of the minute.”
Reader comment“For Impatient Web Users, An Eye Blink Is Too Long to
Wait” The New York Times
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Source: Jakob Nielsen
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“We want you to be able to flick from one page to another as quickly as you can flick a
page on a book. So we’re really aiming very, very high here…
at something like 100 milliseconds.”
Urs HölzleSenior Vice President of Technical
Infrastructure Google
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fast
slow
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“Time is measured objectively
but perceived subjectively, and experiences can
be engineered to improve perceived performance.”
Ilya GrigorikHigh Performance Browser Networking
Progress indicators
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A progress indicator on a page that loads in <5 seconds will make that
page feel slower.
Best case: 10+ seconds
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Progress bars that offer the illusion of a left-moving ripple can improve perceived wait time by up to 10%.
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Progress bars that pulse, and that increase pulsation frequency as
the bar progresses, are perceived as being faster.
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Progress bars that speed up are considered more satisfying by
users.*
*Think back to that colonoscopy research
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But…Use them sparingly.
Images
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When do users start to interact with a page?
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Source: Radware, Progressive JPEGs: Good or Evil?
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“When, as with the Progressive JPEG method, image rendition is a two-stage
process in which an initially coarse image snaps into sharp focus,
cognitive fluency is inhibited and the brain has to
work slightly harder to make sense of what is being displayed.”
Dr. David LewisChair, Mindlab International
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http://www.oreilly.com/pub/e/3425
Defer
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Third-party contentcan make up >50%
of page requests
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Exposes you to data leakageGenerates content security warnings that alarm your visitors and kill your conversionsHurts your Google search rankings (SEO)Makes your site vulnerable to man-in-the-middle security attacks
Potential impact of fourth-party calls
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Original: 3.5s
SPOF: 22.7s
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Popup best practices• Optimize script• Ensure cross-browser
functionality• Delay for at least 10
seconds• A/B test for effectiveness
Measure the right stuff
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First Paint is not equal to Start Render!
Chrome – “First Paint”
True Start Render
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User Timing InterfaceAllows developers to measure performance of their applications through high-precision timestamps
Consists of “marks” and “measures” PerformanceMark: Timestamp PerformanceMeasure: Duration between
two given marks
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How long does it take to display
the main product image on my
site?
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Record when an image loads<img src=“image1.gif” onload=“performance.mark(‘image1’)”>
For more interesting examples:
Measure hero image delayhttp
://www.stevesouders.com/blog/2015/05/12/hero-image-custom-metrics
/
Measure aggregate times to get an “above fold time”
http://blog.patrickmeenan.com/2013/07/measuring-performance-of-user-experience.html
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http://soasta.io/perftimings
Be useful
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A user who was served feature content within the first second of page load
spent 20% of his or her time within the feature area.
A user who was subjected to an 8-second delay of a page’s feature
content spent only 1% of his or her time visually engaging with that area of the
page.
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Source: Jakob Nielsen
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Make the perceived value
of your content worth the wait.
Thanks!
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