The latest in site speed: advanced #webperf 2018

1. Bastian Grimm, Peak Ace AG | @basgr The latest in #webperf 2018: better metrics, images, custom fonts & CRP Web Performance Madness

2. GDPR is actually pretty cool!

3. 3 @peakaceag pa.ag USA Today created a superfast GDPR compliant offering 500 vs. 34 requests, 140 vs. 0 JS files, 6 vs. 1 CSS, 5.01 MB vs. 356 kB in size, etc. EU 0.300 sec 0.345 sec 0.995 sec 443 US 1.700 sec 3.604 sec 19.261 sec 8,792 Start Render First Interactive Load Time Speed Index 34 859Total Requests 356 kB 5,092 kBBytes in

4. Fast loading time plays an important role in overall user experience! Performance = user experience!

5. 5 @peakaceag pa.ag Let’s get this straight – this is what your users expect: Obviously, slow page loading time is a major factor in page abandonment. According to a Nielsen report, 47% of people expect a website to load within two seconds, and 40% will leave a website if it does not load fully within three seconds.”

6. Because the PageSpeed Insights score is not enough! #1 Better measurement

7. 7 @peakaceag pa.ag Translating experiences to performance metrics User experience ▪ Is it happening? › Did the navigation start successfully? Has the server responded? ▪ Is it useful? › Has enough content rendered for users to engage with it? ▪ Is it usable? › Can users interact with the page or is it still busy loading? ▪ Is it smooth/delightful? › Are the interactions smooth and natural, free of lag and jank? Corresponding metric First Paint (FP)/First Contentful Paint (FCP) First Meaningful Paint (FMP) -> Hero Element Timing Time to Interactive (TTI) Long tasks (technically the absence of those long tasks)

8. 8 @peakaceag pa.ag Optimising and measuring for painting timings #1 #2 First Paint (FP) Time to First Paint – marks the point when the browser starts to render something, the first bit of content on the screen.

9. 9 @peakaceag pa.ag Optimising and measuring for painting timings #1 #2 #3 #4 First Paint (FP) First Contentful Paint (FCP) Time to First Paint – marks the point when the browser starts to render something, the first bit of content on the screen. Time to First Contentful Paint – marks the point when the browser renders the first bit of content from the DOM, text, an image etc.

10. 10 @peakaceag pa.ag Optimising and measuring for painting timings #1 #2 #3 #4 #5 #6 First Paint (FP) First Contentful Paint (FCP) First Meaningful Paint (FMP) / Hero! Time to Interactive (TTI) Time to First Paint – marks the point when the browser starts to render something, the first bit of content on the screen. First Meaningful Paint – the paint after which the biggest above-the-fold layout change has happened and your most important element is visible!

11. 11 @peakaceag pa.ag Watching a video on YouTube? This is your hero element:

12. 12 @peakaceag pa.ag Chrome Dev Tools > Performance > Profiling (Frames)

13. 13 @peakaceag pa.ag Track paint timings with Google Analytics (in theory) Get the tracking code snippets: http://pa.ag/2viHQSz version 62 and up You must ensure your PerformanceObserver is registered in the <head> before any stylesheets, so it runs before FP/FCP happens. (a buffered flag TBD in v.2)

14. 14 @peakaceag pa.ag This is how it looks like in Google Analytics Behaviour > events > pages: performance metrics [first-contentful-paint] Source: Google Analytics

15. 15 @peakaceag pa.ag The cool kids’ way of doing this (using GTM) #1 #3 #2 #4 This needs to go directly into your HTML mark-up because GTM doesn’t support ES6 script atm.

16. 16 @peakaceag pa.ag Combine it with Google Data Studio Test it: http://pa.ag/2Ee550q

17. The code and resources required to render the initial view of a web page #2 Critical rendering path

18. 18 @peakaceag pa.ag Critical rendering path optimisation Initial view (critical) Below the fold (not critical)

19. Some brief, technical background:

20. 20 @peakaceag pa.ag CSSOM: the CSS Object Model ▪ The CSSOM is a “map” of the CSS styles found on a web page. ▪ It’s much like the DOM (Document Object Model), but for CSS rather than HTML. ▪ The CSSOM combined with the DOM is used by browsers to display web pages. body font-size:16px; h1 font-size:22px; p font-size:16px; p font-size:12px; a font-size:12px; img font-size:16px;

21. 21 @peakaceag pa.ag Web browsers use the CSSOM to render a page If this is external CSS, the browser needs to wait for the download.

22. 22 @peakaceag pa.ag Google doesn’t make a single GET request for its CSS! Because requesting external CSS is more expensive than inlining everything.

23. 23 @peakaceag pa.ag How to know which CSS is critically required “Critical” renders in multiple resolutions & builds a combined/compressed CRP CSS: Critical & criticalCSS on GitHub: http://pa.ag/2wJTZAu & http://pa.ag/2wT1ST9 ▪ Minimum: a snapshot of CSS rules to render a default desktop resolution (e.g. 1280x1024). ▪ Better: various snapshots for mobile phones, pad/s & desktop/s – manually that’d be a lot of work!

24. 24 @peakaceag pa.ag <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width"> <title>CRP loading demo</title>  <style> h1 { colour: green; } </style>  <link rel="preload" href="non-critical.css" as="style" onload="this.rel='stylesheet'" />  <noscript><link rel="stylesheet" href="non-critical.css"></noscript>  <script> *! loadCSS. [c]2017 Filament Group, Inc. MIT License */ (function(){ ... } ()); /*! loadCSS rel=preload polyfill. [c] 2017 Filament Group, Inc. MIT License */ (function(){ ... } ()); </script> </head> <body> </body> </html>  <link rel="preload" href="non-critical.css" as="style" onload="this.rel='stylesheet'" />  <style> h1 { colour: green; } </style>  <link rel="preload" href="non-critical.css" as="style" onload="this.rel='stylesheet'" />  <noscript><link rel="stylesheet" href="non-critical.css"></noscript> *! loadCSS. [c]2017 Filament Group, Inc. MIT License */ (function(){ ... } ()); /*! loadCSS rel=preload polyfill. [c] 2017 Filament Group, Inc. MIT License */ (function(){ ... } ()); Putting it all together Fit the HTML, CSS & JS that’s necessary for “Start Render” into that first 14 kB round trip! Inline your critical CSS. 1 Loading non-critical CSS async using rel=“preload“. 2 Apply the CSS once it has finished loading via “onload“. 3 Fallback for non-JS requests. 4 Implement loadCSS script for older browsers. 5

25. Let’s look at an implementation… Is it worth all the effort?

26. 26 @peakaceag pa.ag Before & after: a fresh WordPress setup #1 HTTP, no HTTP/2, Twenty Seventeen theme (1x CSS, 8x JS, custom fonts), no caching and no other performance optimisations

27. 27 @peakaceag pa.ag Before & after: a fresh WordPress setup #2 HTTP, no HTTP/2, Twenty Seventeen theme (1x CSS, 8x JS, custom fonts), W3Total (CSS, JS, HTML minify, caching, compression)

28. 28 @peakaceag pa.ag Before & after: a fresh WordPress setup #3 HTTP, no HTTP/2, Twenty Seventeen theme (1x CSS, 8x JS, custom fonts), W3Total (CSS, JS, HTML minify, caching, compression) + CRP CSS inlined

29. 29 @peakaceag pa.ag Performance metrics comparison at a glance Rendering starts significantly earlier; this allows for faster interaction with the site. KPI / MEASUREMENT Load Time Time to First Byte (TTFB) Start Render Time to Interactive (TTI) DEFAULT WP 1.357 sec 0.454 sec 1.000 sec 0.956 sec BASICS (W3TOTAL) 0.791 sec 0.159 sec 0.600 sec 0.931 sec FULLY OPTIMISED 0.789 sec 0.157 sec 0.410 sec 0.563 sec (+32%) (+41%)

30. Highest quality, (more) efficient data compression & smaller files #3 Image optimisation

31. 31 @peakaceag pa.ag 62% of all web traffic is made up of images... … and 51% of all URLs load more than 40 images per request. Source: http://pa.ag/1SGDOEo Average bytes per page by content type Image requests per page

32. 32 @peakaceag pa.ag Basic optimisation for all images: put ‘em on a diet! tinyPNG & tinyJPG for smart (lossy) compression & removal of metadata et al. http://tinypng.com | http://tinyjpg.com

33. 33 @peakaceag pa.ag WebP: Google’s alternative to JPEG, PNG, and GIF Lossy & lossless compression, transparency, metadata, colour profiles, animation, and much smaller files (30% vs. JPEG, 80% vs. PNG) – but only in Chrome, Opera & Android Everything about WebP: http://pa.ag/1EpFWeN / & WebP support: http://pa.ag/2FZK4XS

34. 34 @peakaceag pa.ag You can still use WebP with on-the-fly replacement Swap PNG and JPEG images per re-write (i.e., using .htaccess) VS.

35. 35 @peakaceag pa.ag There is way more: FLIF, BPG, JPEG-XR, etc. If you’re “image-heavy”, play around with it! Further reading: http://pa.ag/1S5OQmX

36. 36 @peakaceag pa.ag SEMrush (blog) could save 80-90% of it’s image traffic Better compression combined with modern image formats (i.e. WebP & JPEG-XR)

37. Pretty, varied, colourful, and often very slow! #4 Custom web fonts

38. 38 @peakaceag pa.ag >70% of all websites use at least one non-standard font! Result: 114 kB of additional data and on average 3 additional HTTP requests Source: http://pa.ag/1BRUnbe Font transfer size & font requests Sites with custom fonts Font transfer size (kB) Font requests

39. 39 @peakaceag pa.ag Classic scenario: using external CSS Easy to use with one big disadvantage: it’s render-blocking! CSS (font) call to Google causes the render to stop / block until the download has been finished!

40. FOIT (flash of invisible text) or FOUT (flash of unstyled text) can cause annoying flickering Asynchronous?

41. 41 @peakaceag pa.ag Fighting the flash of unstyled text/content Make your fall-back font match the intended web font (letter spacing, heights, etc.) Give it a try: https://pa.ag/2qgE8EH

42. 42 @peakaceag pa.ag Fighting the flash of invisible text New stuff to play around with: various “font-display” strategies (no IE/Edge yet) More: http://pa.ag/2eUwVob ‘font-display’ allows to display text while the font for it is still loading!

43. 43 @peakaceag pa.ag Don‘t miss Monica Dinculescu‘s great talk titled „Fontastic Web Performance“ Watch the full talk: https://pa.ag/2qf6hvK

44. 44 pa.ag@peakaceag If you can only do one thing, I’d recommend doing this: 100ms blocking period, but no swap. Even after it’s downloaded (only on next page view) Go to your CSS file, look for @font-face and add ’font-display:optional’ - there hasn’t been a safer & easier gain in #webperf in a long time!

45. 45 @peakaceag pa.ag e-mail me > bg@pa.ag ALWAYS LOOKING FOR TALENT! CHECK OUT JOBS.PA.AG Bastian Grimm bg@pa.ag twitter.com/peakaceag facebook.com/peakaceag www.pa.ag Want the deck? WINNER

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