Web Performance Madness - brightonSEO 2018
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My talk from brightonSEO 2018 covering various web performance strategies, this time mainly focussing on critical rendering path, various image optimisation strategies as well as how to handle custom web fonts.
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Web Performance Madness - brightonSEO 2018
- 1. Bastian Grimm Peak Ace AG Web Performance Madness: Critical Rendering Path Optimisation @basgr http://www.slideshare.net/bastiangrimm
- 2. 2 pa.ag@peakaceag No need to take notes: https://pa.ag/brgh18spd
- 3. Because the PageSpeed Insights score is not enough! #1 Better measurement
- 4. 4 @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)
- 5. 5 @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.
- 6. 6 @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.
- 7. 7 @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!
- 8. 8 @peakaceag pa.ag Watching a video on YouTube? This is your hero element:
- 9. 9 @peakaceag pa.ag Chrome Dev Tools > Performance > Profiling (Frames)
- 10. 10 @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)
- 11. 11 @peakaceag pa.ag This is how it looks like in Google Analytics Behavior > events > pages: performance metrics [first-contentful-paint] Source: Google Analytics
- 12. 12 @peakaceag pa.ag The cool kids’ way of doing this (using GTM) #1 #3 #2 #4
- 13. 13 @peakaceag pa.ag Combine it with Google Data Studio: Test it: http://pa.ag/2Ee550q
- 14. The code and resources required to render the initial view of a web page #2 Critical rendering path
- 15. 15 @peakaceag pa.ag Critical rendering path optimisation Initial view (critical) Below the fold (not critical)
- 16. Some brief, technical background:
- 17. 17 @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;
- 18. 18 @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
- 19. 19 @peakaceag pa.ag Google doesn’t make a single GET request for its CSS! Because requesting external CSS is more expensive than in-lining everything.
- 20. 20 @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!
- 21. 21 @peakaceag pa.ag If you want to play around first: Try criticalcss.com Give it a try: http://pa.ag/2nVIwXB
- 22. 22 @peakaceag pa.ag <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width"> <title>CRP loading demo</title> <!-- critical CSS goes here --> <style> h1 { colour: green; } </style> <!-- use async preload // no IE, Edge & some other unimportant ones (http://caniuse.com/#search=preload) --> <link rel="preload" href="non-critical.css" as="style" onload="this.rel='stylesheet'" /> <!--noscript for req. without JS --> <noscript><link rel="stylesheet" href="non-critical.css"></noscript> <!-- include polyfill for shitty browsers --> <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> <!-- use async preload // no IE, Edge & some other unimportant ones (http://caniuse.com/#search=preload) --> <link rel="preload" href="non-critical.css" as="style" onload="this.rel='stylesheet'" /> <!-- critical CSS goes here --> <style> h1 { colour: green; } </style> <!-- use async preload // no IE, Edge & some other unimportant ones (http://caniuse.com/#search=preload) --> <link rel="preload" href="non-critical.css" as="style" onload="this.rel='stylesheet'" /> <!--noscript for req. without JS --> <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
- 23. Let’s look at an implementation… Is it worth the effort?
- 24. 24 @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 optimizations
- 25. 25 @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)
- 26. 26 @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
- 27. 27 @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 OPTIMIZED 0.789 sec 0.157 sec 0.410 sec 0.563 sec (+32%) (+41%)
- 28. 28 @peakaceag pa.ag TL;DR Implement proper tracking, measure “First Meaningful Paint” (Hero Element delivery). Audit, clean and (afterwards) split CSS into two parts: “initial view” and “below the fold”. Use “critical” to generate and inline your critical path CSS. Use rel=“preload“ and “loadCSS” to async load below the fold / site-wide CSS. Off-load all overhead (JS, etc.) to stay within 14kB for faster, initial paint.
- 29. Highest quality, (more) efficient data compression & smaller files. #3 New image formats
- 30. 30 @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
- 31. 31 @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
- 32. 32 @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.
- 33. 33 @peakaceag pa.ag There is way more: FLIF, BPG, JPEG-XR, etc. If you’re “image-heavy”, go play with it! Further reading: http://pa.ag/1S5OQmX
- 34. 34 @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)
- 35. 35 @peakaceag pa.ag Please DON’T use a 1.2 MB background image, Kelvin? Seriously, this can be as small as 83 KB (PNG) or even 17 KB (WebP)!
- 36. Pretty, varied, colourful, and often very slow! #4 Custom web fonts
- 37. 37 @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
- 38. 38 @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!
- 39. FOIT (flash of invisible text) or FOUT (flash of unstyled text) can cause annoying flickering Asynchronous?
- 40. 40 @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
- 41. 41 @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!
- 42. 42 @peakaceag pa.ag Don‘t miss Monica Dinculescu‘s great talk titled „Fontastic Web Performance“ Watch the full talk: https://pa.ag/2qf6hvK
- 43. 43 pa.ag@peakaceag If you can only do one thing, I’d recommend doing this: 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!
- 44. 44 pa.ag@peakaceag We’re hiring! 25+ Performance Marketing jobs in Berlin! Come and say “hello” or apply via jobs.pa.ag. Looking forward to speaking to you! Always looking for talent! Check out jobs.pa.ag
- 45. 45 @peakaceag pa.ag http://pa.ag/brgh18spd Always looking for talent! Check out jobs.pa.ag Bastian Grimm bg@pa.ag twitter.com/peakaceag facebook.com/peakaceag www.pa.ag Liked the deck? Here you go: