Who????

What is Responsive images?

Efficiently load properly dimensioned images that fit the page's design

<history>

Mobile Web

Mobile Web

And then

RWD

• Media Queries
• Fluid grids
• Flexible images

"Flexible images???"

"That's easy"

"Just send the largest possible image"

"And let the browser resize it"

All done!!!

BLOAT!!!

72% Serve same resources

guypo.com

Which resources?

Images - over 63%

httparchive.org

How much can be saved?

Up to™ 72% image data savings

data plan abuse

People demanded a solution

Turned to the mailing lists

Proposals!

Moar proposals!

And MOAR!!!

<picture> proposal

srcset proposal

Picture vs. srcset!

Picture *and* srcset

Browsers weren't convinced

9 months later

Src-N

Moar proposals???

Back to picture

Mozilla were positive

Blink tho

So, crowdfunding to the rescue

Patches got landing

~80 patches later

Blink work is done

WebKit is half way through

Shipped in Chrome 38

A group effort

</history>

<syntax>

The srcset 'x' part

Use case

"Retina images"

Load hi-res images

on hi-res devices

<img src="1x.jpg" 
    srcset="2x.jpg 2x, 2.6x.jpg 2.6x" 
     alt="A giraffe.">

The <picture> part

Use case

Art direction

<picture>
     <source media="(min-width: 45em)" 
               srcset="large.jpg">
     <source media="(min-width: 18em)" 
               srcset="medium.jpg">
     <img src="small.jpg" alt="The president.">
</picture>

Use case #2 - MIME type fallback

Mime type fallback syntax

<picture>
     <source type="image/webp" 
               srcset="prez.webp">
     <source type="image/vnd.ms-photo" 
               srcset="prez.jpx">
     <img src="prez.jpg" alt="The president.">
</picture>

The sizes + srcset 'w' descriptor part

use case

variable width images

<img src="panda.jpg" 
     sizes="100vw"
     srcset="panda200.jpg 200w, 
             panda400.jpg 400w, 
             panda800.jpg 800w,
             panda1200.jpg 1200w, 
             panda2400.jpg 2400w"
     alt="A panda.">

<img src="senator.jpg" 
     sizes="44vw"
     srcset="senator200.jpg 200w, 
             senator400.jpg 400w, 
             senator800.jpg 800w,
             senator1200.jpg 1200w, 
             senator2400.jpg 2400w"
     alt="A senator.">

But wait, there's more

<img src="thumb.jpg" 
     sizes="(min-width: 1200px) 235px,
          (min-width: 641px) 24vw,
          (min-width: 470px) 235px,
          50vw"
     srcset="thumb100.jpg 100w, 
             thumb200.jpg 200w, 
             thumb235.jpg 235w, 
             thumb470.jpg 470w"
     alt="Some animal.">

Separation of concerns?

`sizes` is an optimization

All together now

<picture>
    <source media="(min-width: 641px)"
            sizes="(max-width: 1600px) 100vw,
                   1600px"
            srcset="sloth_bg_640.jpg 640w,
                    sloth_bg_960.jpg 960w, ...">
    <img src="sloth.jpg" 
         srcset="sloth_320.jpg 320w, 
                 sloth_480.jpg 480w, ..."
         alt="A rad sloth.">
</picture>

<img src="icecream.jpg" 
     sizes="(max-width: 500px) 100vw,
            500px"
     srcset="icecream_250.jpg 250w, 
             icecream_500.jpg 500w, ..."
     alt="Minions on an icecream break">

</syntax>

<support>

srcset 'w' usage

<picture> usage

srcset 'x' usage

</support>

<advice>

To picturefill or

<picture> or srcset?

Source order matters

<picture>
     <source media="(min-width: 45em)" 
               srcset="large.jpg">
     <source media="(min-width: 18em)" 
               srcset="medium.jpg">
     <img src="small.jpg" alt="The president.">
</picture>

!=

<picture>
     <source media="(min-width: 18em)" 
               srcset="medium.jpg">
     <source media="(min-width: 45em)" 
               srcset="large.jpg">
     <img src="small.jpg" alt="The president.">
</picture>

Source-size order matters

sizes="(max-width: 30em) 100vw, 
     (max-width: 50em) 50vw, 
     calc(33vw - 100px)"

!=

sizes="(max-width: 50em) 50vw,
     (max-width: 30em) 100vw, 
     calc(33vw - 100px)"

'sizes' default value

Styling

"Picture is a magical span, nothing more"

- Tab Atkins

Alternative text

Future compat

Feature detection FTW!

HTMLImageElement.sizes & HTMLPictureElement

Which resource was picked?

HTMLImageElement.currentSrc

</advice>

What's in the future?

Client Hints

Content negotiation

Accept-CH

DPR

RW

Content-DPR

Status

To sum it up

Start using that. TODAY!

Start with srcset

The Web is ours!

Thanks!

@yoavweiss on Twitter & GitHub

responsiveimages.org

yoavweiss.github.io/smashingconf_oxford

Questions?