HK CodeConf 2015 - Your WebPerf Sucks
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These are the slides from my talk "Your WebPerf Sucks" at HK CodeConf 2015 (http://hongkong.codeconf.io) at Science Park in Hong Kong, October 24th. Web Performance is an important aspect of building for the web and this talk highlights different aspects of what is important and what can be done to improve web performance and build faster sites. While mentioning different aspects of possible improvements, the main focus lies on optimising the critical rendering path to get pages on the screen faster and what tools can help to do so.
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HK CodeConf 2015 - Your WebPerf Sucks
- 1. Your WebPerf is ! Holger Bartel | @foobartel | HK CodeConf 23/10/2015
- 2. So, why?
- 4. 42 requests, 6.3 MB
- 6. 250 requests, 6.7 MB
- 7. "
- 9. 86 requests, 10.2 MB
- 10. Performance is a thing.
- 11. Users expect ~2-3 seconds to load a site… Expectations
- 12. Users expect ~2-3 seconds to load a site… That’s the definition of ‘fast’ We’re even aiming to deliver something in even less Expectations
- 13. 50% of people say they'll abandon a page that takes longer than 4 seconds to load Expectations
- 14. Faster is Be er!
- 15. So, why?
- 16. The Real World (and why you should care)
- 17. 40% of surveyed online shoppers will abandon a page that takes more than 3 seconds to load. — Akamai (2009)
- 18. Speeding up a fundraising site by 60% increased donations by 14%. — Kyle Rush, Obama Campaign (2012)
- 19. Adding half a second to a search results page can decrease traffic and ad revenues by 20 percent — Google
- 20. Every additional 100 milliseconds of load time decreased sales by 1 percent. — Amazon
- 21. Images - The Big Evil (and an easy fix)
- 23. Original Optimised 2 MB @ 298 x 530 73 KB ImageOptim App
- 24. 01 Oct 2012 - 15 Oct 2014 http://httparchive.org/interesting.php
- 25. http://httparchive.org/interesting.php 01 Oct 2014 - 01 Oct 2015
- 27. Performance is Design Design is Performance
- 28. Performance is Design Design is Performance Design directs Performance
- 29. — Ian Feather “Performance is a compromise between design and performance. You can only be as fast as the design allows.”
- 30. Collaboration & communication between designers and developers nowadays is essential and more important than ever before. Breaking Silos
- 31. Get designs into the browser as soon as possible, so you, your team and your client can get a be er feel for what it will be like in the real world.
- 32. If your website is 15MB it’s not HTML5, it’s stupid. — Christian Heilmann
- 33. Ask yourself: What's the gain? What do you want to achieve?
- 34. A carousel with 7 images - is it really worth the load time or just pre y to look at?
- 35. Whereas it's questionable if images 3-7 will be seen in the first place.
- 37. Rendering Pages
- 38. Waiting for DOM and CSSOM to build the render tree. Render tree contains nodes to render the page. Layout computes the exact position and size. Paint turns the render tree into pixels on screen. Render-Tree Construction, Layout & Paint
- 39. Wait for CSS Avoids “Flash of Unstyled Content” (FOUC) Render Blocking CSS
- 40. The parser has to stop for scripts before continuing to parse HTML. JavaScript can query and modify DOM and CSSOM. JavaScript blocks DOM construction unless explicitly declared as async. Render Blocking JavaScript
- 41. Every request fetched inside of HEAD, will postpone the rendering of the page Loading Assets
- 42. Every request takes roughly ~200ms Avoid unnecessary redirects Limit HTTP Requests
- 43. Critical Resource Critical Path Length Critical Bytes Critical Rendering Path
- 44. Optimising the dependency graph between HTML, CSS, and JavaScript. Optimising the Critical Rendering Path
- 45. Optimising the Critical Rendering Path = Ge ing ! on the screen fast
- 46. To get our li le friend ! on the screen fast…
- 47. Minimise the number of critical resources. Minimise the number of critical bytes. Minimise the critical path length. A critical resource is a resource that can block initial rendering of a page.
- 48. Analyse and characterise: number of resources, bytes, length. Minimise number of critical resources. Optimise order of remaining critical resources being loaded: download critical assets as early as possible. Optimise the number of critical bytes to reduce the download time (number of roundtrips).
- 51. Tools
- 54. Chrome Dev Tools
- 58. With achieving fast page load time, people can quickly use your site and accomplish what they want.
- 59. People will appreciate it and end up being happier users.
- 60. Happier users mean be er conversion rates. Be er conversion rates can be increased revenue, more signups, returning visits, or downloads.
- 61. Let’s make the web less ! So…
- 62. Thanks! Holger Bartel | @foobartel | HK CodeConf 23/10/2015