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@towebperf
Tweet!
#towebperf
!
!
DAVID NEWTON (@NEWTRON)
RESPONSIVE IMAGES
BLAKE CROSBY (@BLAKECROSBY)
THE IMPORTANCE OF A CDN
HELLO!
& Review!
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Improving Performance
with Responsive Images
Toronto Web Performance Group
January 22, 2014
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–Brad Frost
“Good performance is good design”
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–Anand Giridharadas, New York Times, April 10 2010
“More human beings today have access to a
cellphone than the United Nations says have
access to a clean toilet.”
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–Anand Giridharadas, New York Times, April 10 2010
“More human beings today have access to a
cellphone than the United Nations says have
access to a clean toilet.”
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1. A flexible, grid-based layout,
2. Flexible images and media, and
3. Media queries, a module from the CSS3
specification
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1. A flexible, grid-based layout,
2. Flexible images and media, and
3. Media queries, a module from the CSS3
specification
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img {
max-width: 100%;
}
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A solution
Serve one big image and
let the browser scale it
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• Average web page size: 1,681 KB
• Images account for 1,031 KB, over 61% of total
!
HTTP Archive, January 15 2014
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2x resolution = 4x as many pixels
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–Brad Frost
“Good performance is good design”
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A better solution
Serve an appropriately-sized image
to each user
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Responsive Images
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SVG, WebP, JPEG XR
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• : http://picture.responsiveimages.org/
• srcset: http://www.w3.org/html/wg/drafts/srcset/
w3c-srcset/
• Client Hints: http://tools.ietf.org/html/draft-grigorik-
http-client-hints-01
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http://picture.responsiveimages.org/
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Performance wins
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Resource Priorities
http://www.w3.org/TR/resource-priorities/
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When can we expect
this to work?
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What can you do now?
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ImageOptim-CLI
http://jamiemason.github.io/ImageOptim-CLI/
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Use fewer images
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SVG
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Picturefill
https://github.com/scottjehl/picturefill
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• Art direction
• Viewport switching (using MQs)
• DPR switching (using MQs)
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data-media="(min-device-pixel-ratio: 1.5),
(min-resolution: 144dpi)"
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• Art direction
• Viewport switching (using MQs)
• DPR switching (using MQs)
• Resolution switching (using srcset)
• File type switching
• Resource priorities
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• Art direction
• Viewport switching (using MQs)
• DPR switching (using MQs)
• DPR switching (using srcset)
• File type switching
• Resource priorities
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Picturefull
https://github.com/nwtn/picturefill
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...
...
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Impact
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No optimizations
• 11 HTTP requests
• 2.9MB of data transferred
• 3.72s load time
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No optimizations
• 11 HTTP requests
• 2.9MB of data transferred
• 3.72s load time
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Optimizations
• 14 HTTP requests
• 476KB of data transferred (~84% savings)
• 1.26s load time (~66% savings)
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Optimizations
• 14 HTTP requests
• 476KB of data transferred (~84% savings)
• 1.26s load time (~66% savings)
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Optimizations + RP
• 5 HTTP requests
• 235KB of data transferred (~92% savings)
• 1.11s load time (~70% savings)
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Optimizations + RP
• 5 HTTP requests
• 235KB of data transferred (~92% savings)
• 1.11s load time (~70% savings)
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David Newton!
@newtron on Twitter
@nwtn on GitHub
david@davidnewton.ca