This document discusses optimizing images for fast loading on mobile websites. It provides 4 simple optimizations: 1) reducing image quality, 2) using optimized formats like JPEG, PNG and WebP, 3) proper sizing of images for different screen widths, and 4) lazy loading images below the fold. The document shows how these techniques can significantly reduce image file sizes and page load times based on analyzing millions of real-world mobile sites.

1. Delivering Fast and Beautiful Images
Doug Sillars
@DougSillars
Seattle VueJS
June 24, 2019

2. Contact Me:
@DougSillars
Doug.Sillars@gmail.com
www.dougsillars.com
Doug Sillars
Freelance Developer Relations
Performance Audits: Web/Native
Workshops:
Performance/Images/Video/AR
http://bit.ly/HighPerformanceAndroidApps

4. 0.5
0.6
0.7
0.8
0.9
Standing in Line Standing on the
edge of a virtual
cliff
Experiencing
Mobile Delays
Solving a Math
Problem
https://www.ericsson.com/res/docs/2016/mobility-report/emr-feb-2016-the-stress-of-steaming-delays.pdf
Stress

5. Large Downloads Induce Delays in Rendering
3s: 53% of Users Abandon Mobile Sites
500ms: 26% Frustration
8% Engagement
100ms: 1% Revenue Walmart & Amazon (Desktop 2001)
4% Mobile Users Throw Their Phones
https://www.doubleclickbygoogle.com/articles/mobile-speed-matters
http://bit.ly/mobileWebStress
http://www.globaldots.com/how-website-speed-affects-conversion-rates/
https://www.mobilejoomla.com/blog/172-responsive-design-vs-server-side-solutions-infographic.html

6. Images Dominate the Web
HTTPArchive mobile websites 04/2019

7. 4 Simple Image Optimizations

8. 4 Simple Image Optimizations
1. Quality
2. Format
3. Sizing
4. Lazy Loading

9. 4 Simple Image Optimizations
1. Quality
2. Format
3. Sizing
4. Lazy Loading

10. 4 Simple Image Optimizations
Httparchive.org Webpagetest.org

11. 4 Simple Image Optimizations
1. Quality
2. Format
3. Sizing
4. Lazy Loading

12. Image Quality
magick -quality 85 riga.jpg riga85.jpg
http://res.cloudinary.com/dougsillars/image/upload/q_85/v1520504964/IMG_20180301_114117_tzasan.jpg
Lighthouse:
Recommends 85% quality on all images
https://developers.google.com/speed/docs/insights/OptimizeImages

13. 100%
3.6 MB
http://res.cloudinary.com/dougsillars/image/upload/v1529005982/IMG_20180614_184507_ssuk1i.jpg

14. 85%
1.87 MB
q_85
http://res.cloudinary.com/dougsillars/image/upload/q_85/v1529005982/IMG_20180614_184507_ssuk1i.jpg

15. Image Quality Use “In The Wild”
500,000 mobile sites
Analyzed 3/15/18

16. Image Quality Use “In The Wild”
5M mobile sites
Analyzed May 1, 2019
48% score 1
10% score 0
32% score < 0.5

17. Image Quality Use “In The Wild”
Median Savings (50th percentile):
• 2.83 seconds faster page load
• 419KB less data

18. Image Quality Use “In The Wild”
Median Savings (50th percentile):
• 3.7 seconds faster page load
• 133 KB less data

19. Image Quality Use “In The Wild”
Median Savings (50th percentile):
• 9.7 seconds faster page load
• 1.6 MB less data

20. 50%
914 KB
q_50
http://res.cloudinary.com/dougsillars/image/upload/q_50/v1529005982/IMG_20180614_184507_ssuk1i.jpg

21. 20%
513 KB
q_20
http://res.cloudinary.com/dougsillars/image/upload/q_20/v1529005982/IMG_20180614_184507_ssuk1i.jpg

22. Graphing the Results
https://developers.google.com/speed/docs/insights/OptimizeImages

23. Graphing the Results
https://developers.google.com/speed/docs/insights/OptimizeImages

24. Automate Quality vs. File Size
• Butteraugli
• SSIM: Structural SIMilarity
https://github.com/technopagan/cjpeg-dssim
cjpeg-dssim jpegoptim riga.jpg
http://res.cloudinary.com/dougsillars/image/upload/q_auto/v1529005982/IMG_20180614_184507_ssuk1i.jpg

25. SSIM
1.46 MB
http://res.cloudinary.com/dougsillars/image/upload/q_auto/v1529005982/IMG_20180614_184507_ssuk1i.jpg

26. Graphing the Results
https://developers.google.com/speed/docs/insights/OptimizeImages

27. Results:
• Test Load on Motorola G4:

28. 4 Simple Image Optimizations
1. Quality
2. Format
3. Sizing
4. Lazy Loading

29. Image Formats – Average Size
HTTPArchive mobile websites 15/02/18

30. Image Formats – Average Size
HTTPArchive mobile websites 15/02/18

31. Scalable Vector Graphics (SVG)
Images drawn as shapes
infinitely scalable
XML - Can be added inline to HTML document
https://gist.github.com/hail2u/2884613?short_path=66a60ff

32. Scalable Vector Graphics (SVG)
Images drawn as shapes
infinitely scalable
XML - Can be added inline to HTML document
https://gist.github.com/hail2u/2884613?short_path=66a60ff

33. Scalable Vector Graphics (SVG)

34. Scalable Vector Graphics (SVG)

35. Scalable Vector Graphics (SVG)
KB
Original 946
Optimized 1

36. Scalable Vector Graphics (SVG)
KB
Original 946
Optimized 1

37. Scalable Vector Graphics (SVG)
KB
Original 946
Optimized 1
GZip 687 bytes

38. Scalable Vector Graphics (SVG)
KB
Original 946
Optimized 1
GZip 687 bytes
Brotli 525 bytes

39. Scalable Vector Graphics (SVG)
KB
Original 946
Optimized 1
GZip 687 bytes
Brotli 525 bytes

40. Scalable Vector Graphics (SVG)
<style >
.svgorange {
filter: invert(.5) sepia(1)
saturate(5) hue-rotate(5deg);
}
</style>
<img class="svgorange" src ="map-
marker-circle.svg">
https://medium.com/@union_io/swapping-fill-color-on-image-tag-svgs-using-css-filters-fa4818bf7ec6

41. Scalable Vector Graphics (SVG)

42. Image Formats – Average Size
HTTPArchive mobile websites 15/02/18

43. Image Formats – PNGs
https://dougsillars.com/2019/02/10/using-screenshots-in-production/

44. Image Formats – Screenshots -> JPG
https://dougsillars.com/2019/02/10/using-screenshots-in-production/

45. Image Formats – Average Size
HTTPArchive mobile websites 15/02/18

46. File Format: WebP
https://caniuse.com/#feat=webp

47. SSIM + WebP
986 KB
http://res.cloudinary.com/dougsillars/image/upload/q_auto,f_auto/v1529005982/IMG_20180614_184507_

48. File Format: Web
<picture>
<source width = "100%" type="image/webp" srcset=”riga.webp">
<img width = "100%" src=”riga_cjpeg_dssim.jpg"
alt=”Riga, Latvia">
</picture>

49. Image Format Use “In The Wild”
500,000 mobile sites
Analyzed 3/15/18

50. Image Format Use “In The Wild”
5M mobile sites
Analyzed 5/1/19
18% score 1
28% score 0
62% score <0.5

51. Image Format Use “In The Wild”
500,000 mobile sites
Analyzed 3/15/18

52. Image Format Use “In The Wild”
5M mobile sites
Analyzed 5/1/19
Median page:
139 KB less data
6.6s faster load

53. Image Format Use “In The Wild”
5M mobile sites
Analyzed 5/1/19
Median page:
2.4 MB less data
15s faster load

54. 4 Simple Image Optimizations
1. Quality
2. Format
3. Sizing
4. Lazy Loading

55. Image Sizing
-

56. Image Sizing

57. Image Sizing
-

58. Image Sizing
624
832
-

59. Image Sizing
624
832
12,979,000 pixels
519,000 pixels
_________________
-
12,460,000 pixels

60. Image Sizing
624
832
12,979,000 pixels
519,000 pixels
_________________
-
12,460,000 pixels

61. Image Processing
1M
pixels
Download (s) Image Decode
(ms)
Desktop 14 78
Moto G4 14.2 218
Alcatel 1X 14.2 820

62. Image Sizing
https://twitter.com/paulcalvano/status/928751141843808256

63. Image Sizing
-
Responsive Images:
Generate a set of images
25 KB difference in size

64. Responsive Images
624
832
625,000 pixels
-
106,000 pixels
519,000 pixels
_________________

65. Responsive Breakpoint Generation
https://github.com/cloudinary/responsive_breakpoints_generator
http://www.responsivebreakpoints.com/

66. Responsive Images

67. Responsive Images Use “In The Wild”
500,000 mobile sites
Analyzed 3/15/18

68. Responsive Images Use “In The Wild”
5M mobile sites
Analyzed 5/1/19
58% score 1
8% score 0
26% score <0.5

69. Responsive Images Use “In The Wild”
442,000 mobile sites
Analyzed 3/15/18

70. Responsive Images Use “In The Wild”
5M mobile sites
Analyzed 5/1/19
Median page saves:
130KB data
1.6s faster load

71. Responsive Images Use “In The Wild”
5M mobile sites
Analyzed 5/1/19
Median page saves:
2.4 MB data
14s faster load

72. 4 Simple Image Optimizations
1. Quality
2. Format
3. Sizing
4. Lazy Loading

73. Lazy Load
https://calendar.perfplanet.com/2017/progressive-image-loading-using-intersection-observer-and-sqip/

74. Lazy Load
https://calendar.perfplanet.com/2017/progressive-image-loading-using-intersection-observer-and-sqip/

75. Lazy Loading Use “In The Wild”
442,000 mobile sites
Analyzed 3/15/18

76. Lazy Loading Use “In The Wild”
442,000 mobile sites
Analyzed 3/15/18

77. Preview Images

78. Optimizing Content Delivery
Preview Images
https://github.com/technopagan/sqip

79. Lazy Loading: Experiments

80. Lazy Loading: Chrome Experiments

81. Lazy Loading: Chrome Experiments

82. Animated GIFs
Original MP4
1.4 MB

83. Animated GIFs

84. Animated GIFs
Animated GIF
3.8 MB
270% larger

85. Animated GIFs
“The Graphics Interchange Format is not
intended as a platform for animation, even
though it can be done in a limited way.”
-GIF89a Specification
https://www.w3.org/Graphics/GIF/spec-gif89a.txt

86. Animated GIFs

87. Animated GIFs
MP4: 256 colors
247KB
93% smaller

88. Animated GIFs: Social Media

89. Animated GIFs: Social Media
#FAKENEWS

90. Animated GIFs: Social Media

91. Animated GIFs: as Video!
Video Tags:
<video loop autoplay muted playsinline controls = "false” src="goats.mp4”/>
Img tags are fast!
<picture>
<source type="video/mp4" srcset=”goats.mp4">
<source type="image/webp" srcset=”goats.webp">
<img src=”goats.gif">
</picture>
https://calendar.perfplanet.com/2017/animated-gif-without-the-gif/

92. Animated GIFs

93. Addendum: What Are Your Customers Saying?

94. Addendum: Save-Data
Save-Data: on

95. Addendum: Save-Data

96. Addendum: Save-Data
q_auto -> q_auto:eco
180KB -> 135 KB
https://res.cloudinary.com/dougsillars/image/upload/w_1400,q_auto/v1540978150/IMG_20181028_153301_okeb2b.jpg

97. Addendum 2: Network Info

98. Addendum 2: Network Info
// Network type that browser uses
navigator.connection.type;
// Effective bandwidth estimate
navigator.connection.downlink
// Effective round-trip time estimate
navigator.connection.rtt
// Upper bound on the downlink speed of the first network hop
navigator.connection.downlinkMax

99. Addendum 2: Network Info
// Network type that browser uses
navigator.connection.type;
// Effective bandwidth estimate
navigator.connection.downlink
// Effective round-trip time estimate
navigator.connection.rtt
// Upper bound on the downlink speed of the first network hop
navigator.connection.downlinkMax
500 KBPS

100. Conclusion
Optimize Image:
Quality
Format
Sizing
Lazy Load if Possible
aGIFs to movies
No Base64 Encoded Images
Monitor Customer’s headers
Images

101. Summary
Testing:
WebPageTest https://www.webpagetest.org
HttpArchive https://httparchive.org
Images:
ImageMagick https://www.imagemagick.org
SSIM https://github.com/technopagan/cjpeg-dssim
LazySizes https://github.com/aFarkas/lazysizes
Responsive Breakpoints http://www.responsivebreakpoints.com/
Cloudinary https://www.cloudinary.com
Tooling

102. Conclusion
Images CAN Be Beautiful AND Fast

103. Love Building with Video and Images?
Media Developer Expert
mde-comm@cloudinary.com
Become a