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High Performance Web Sites best practices for faster pages

High Performance Web Sites best practices for faster pages. Steve Souders souders@google.com http://stevesouders.com/docs/webguild.ppt. Speed Matters. users notice pride in our work engineering best practices Google: +500 ms  -20% traffic * Amazon: +100 ms  -1% sales *.

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High Performance Web Sites best practices for faster pages

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  1. High Performance Web Sitesbest practices for faster pages Steve Souders souders@google.com http://stevesouders.com/docs/webguild.ppt

  2. Speed Matters users notice pride in our work engineering best practices Google: +500 ms  -20% traffic* Amazon: +100 ms  -1% sales* *http://home.blarg.net/~glinden/StanfordDataMining.2006-11-29.ppt

  3. The Importance of Frontend Performance Backend: 5% Frontend: 95% Even primed cache, frontend = 88%

  4. Time Spent on the Frontend

  5. The Performance Golden Rule 80-90% of the end-user response time is spent on the frontend. Start there. • Greater potential for improvement • Simpler • Proven to work

  6. Performance Research

  7. Browser Cache Experiment Add a pixel image to the page: Expires: Thu, 15 Apr 2004 20:00:00 GMT Last-Modified: Wed, 28 Sep 2006 23:49:57 GMT # users with at least one 200 response total # unique users users with empty cache page views with empty cache # of 200 responses total # responses

  8. Browser Cache Expt Results percentage 200 responses 40-60% users withempty cache 20% page views with empty cache

  9. Experiment Takeaways empty cache user experience is more prevalent than you think! a majority of page views are done with a primed cache need to optimize for both

  10. 14 Rules

  11. 14 Rules • Make fewer HTTP requests • Use a CDN • Add an Expires header • Gzip components • Put stylesheets at the top • Move scripts to the bottom • Avoid CSS expressions • Make JS and CSS external • Reduce DNS lookups • Minify JS • Avoid redirects • Remove duplicate scripts • Configure ETags • Make AJAX cacheable

  12. Evangelism

  13. High Performance Web Sites September 2007 October 2007: • Slashdot • Amazon: #1 in Computers & Internet Today:

  14. http://developer.yahoo.com/yslow/ performance lint tool grades web pages for each rule Firefox add-on integrated with Firebug open source lincense

  15. Ten Top U.S Web Sites

  16. Strong Correlation total page weight response time inverse YSlow grade correlation(resp time, page weight) = 0.94 correlation(resp time, inverse YSlow) = 0.76

  17. 14 Rules

  18. Rule 1: Make fewer HTTP requests CSS sprites combined scripts, combined stylesheets image maps inline images

  19. CSS Sprites size of combined image is less <span style=" background-image: url('sprites.gif'); background-position: -260px -90px;"> </span>

  20. Rule 2: Use a CDN distribute your static content before distributing your dynamic content

  21. Rule 3: Add an Expires header not just for images

  22. Rule 4: Gzip components you can affect users' download times 90%+ of browsers support compression

  23. Gzip: not just for HTML gzip scripts, stylesheets, XML, JSON (not images, PDF)

  24. Rule 5: Put stylesheets at the top stylesheets block rendering in IE solution: put stylesheets in HEAD (per spec) avoids Flash of Unstyled Content use LINK (not @import)

  25. Rule 6: Move scripts to the bottom scripts block parallel downloads across all hostnames scripts block rendering of everything below them in the page script defer attribute is not a solution • blocks rendering and downloads in FF • slight blocking in IE

  26. Rule 7: Avoid CSS expressions used to set CSS properties dynamically in IE width: expression( document.body.clientWidth < 600 ? “600px” : “auto” ); problem: expressions execute many times • mouse move, key press, resize, scroll, etc. alternatives: • one-time expressions • event handlers

  27. Rule 8: Make JS and CSS external inline: HTML document is bigger external: more HTTP requests, but cached variables • page views per user (per session) • empty vs. primed cache stats • component re-use external is typically better extra credit: post-onload download, dynamic inlining

  28. Rule 9: Reduce DNS lookups typically 20-120 ms block parallel downloads OS and browser both have DNS caches

  29. Rule 10: Minify JavaScript minify inline scripts, too

  30. Minify vs. Obfuscate minify – it's safer not much difference

  31. Rule 11: Avoid redirects 3xx status codes – mostly 301 and 302 HTTP/1.1 301 Moved Permanently Location: http://stevesouders.com/newuri add Expires headers to cache redirects worst form of blocking

  32. Rule 12: Remove duplicate scripts hurts performance • extra HTTP requests (IE only) • extra executions atypical? • 2 of 10 top sites contain duplicate scripts team size, # of scripts

  33. Rule 13: Configure ETags unique identifier returned in response ETag: "c8897e-aee-4165acf0" Last-Modified: Thu, 07 Oct 2004 20:54:08 GMT used in conditional GET requests If-None-Match: "c8897e-aee-4165acf0" If-Modified-Since: Thu, 07 Oct 2004 20:54:08 GMT if ETag doesn't match, can't send 304 ETag format • Apache: inode-size-timestamp • IIS: Filetimestamp:ChangeNumber Use 'em or lose 'em • Apache: FileETag none • IIS: http://support.microsoft.com/kb/922703/

  34. Rule 14: Make AJAX cacheable XHR, JSON, iframe, dynamic scripts can still be cached (and minified, and gzipped) a personalized response should still be cacheable for that person

  35. Next Rules http://news.google.com split dominant content domains reduce cookie weight make static content cookie-free minify CSS use iframes wisely optimize images

  36. Live Analysis

  37. Takeaways focus on the frontend harvest the low-hanging fruit small investment up front keeps on giving you do control user response times LOFNO – be an advocate for your users

  38. Steve Souders souders@yahoo-inc.com

  39. CC Images Used "Need for Speed" by Amnemona: http://www.flickr.com/photos/marinacvinhal/379111290/ "Max speed 15kmh" by xxxtoff: http://www.flickr.com/photos/xxxtoff/219781763/ "maybe" by Tal Bright: http://www.flickr.com/photos/bright/118197469/ "takeout" by dotpolka: http://www.flickr.com/photos/dotpolka/249129144/ "Absolutely Nothing is Allowed Here" by Vicki & Chuck Rogers: http://www.flickr.com/photos/two-wrongs/205467442/ "Zipper Pocket" by jogales: http://www.flickr.com/photos/jogales/11519576/ "Robert's Legion" by dancharvey: http://www.flickr.com/photos/dancharvey/2647529/ "thank you" by nj dodge: http://flickr.com/photos/nj_dodge/187190601/ "new briefcase" by dcJohn: http://www.flickr.com/photos/dcjohn/85504455/

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