1. Steve Souders souders@google.com http://stevesouders.com/docs/widget-summit-2008.ppt High Performance Widgets Disclaimer: This content does not necessarily reflect the opinions of my employer.

2. 17% 83% iGoogle, primed cache The Importance of Frontend Performance 9%91% iGoogle, empty cache

3. Time Spent on the Frontend Empty CachePrimed Cache www.aol.com97% www.ebay.com95%81% www.facebook.com95%81% www.google.com/search47%0% search.live.com/results67%0% www.msn.com98%94% www.myspace.com98% en.wikipedia.org/wiki94%91% www.yahoo.com97%96% www.youtube.com98%97% April 2008

4. 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

5. 14 Rules 1.Make fewer HTTP requests 2.Use a CDN 3.Add an Expires header 4.Gzip components 5.Put stylesheets at the top 6.Put scripts at the bottom 7.Avoid CSS expressions 8.Make JS and CSS external 9.Reduce DNS lookups 10.Minify JS 11.Avoid redirects 12.Remove duplicate scripts 13.Configure ETags 14.Make AJAX cacheable

6. High Performance Web Sites YSlow

7. http://conferences.oreilly.com/velocity/ June 22-24, 2009

9. High Performance Web Sites, Vol 2 1.Split the initial payload 2.Load scripts without blocking 3.Don't scatter inline scripts 4.Split dominant domains 5.Make static content cookie-free 6.Reduce cookie weight 7.Minify CSS 8.Optimize images 9.Use iframes sparingly 10.To www or not to www

10. AOL eBay Facebook MySpace Wikipedia Yahoo! Why focus on JavaScript? YouTube

11. Scripts Block blocks parallel downloads and rendering What's "Cuzillion"? http://stevesouders.com/cuzillion/?ex=10008

12. JavaScript Functions Executed before onload www.aol.com115K30% www.ebay.com183K44% www.facebook.com1088K 9% www.google.com/search15K45% search.live.com/results17K24% www.msn.com131K31% www.myspace.com297K18% en.wikipedia.org/wiki114K32% www.yahoo.com321K13% www.youtube.com240K18% 26% avg 252K avg Initial Payload and Execution

13. Split the initial payload split your JavaScript between what's needed to render the page and everything else load "everything else" after the page is rendered separate manually (Firebug); tools needed to automate this (Doloto from Microsoft) load scripts without blocking – how?

14. MSN Scripts and other resources downloaded in parallel! How? Secret sauce?! var p= g.getElementsByTagName("HEAD")[0]; var c=g.createElement("script"); c.type="text/javascript"; c.onreadystatechange=n; c.onerror=c.onload=k; c.src=e; p.appendChild(c) MSN.com: Parallel Scripts

15. Advanced Script Loading XHR Eval XHR Injection Script in Iframe Script DOM Element Script Defer document.write Script Tag

16. XHR Eval script must have same domain as main page must refactor script var xhrObj = getXHRObject(); xhrObj.onreadystatechange = function() { if ( xhrObj.readyState != 4 ) return; eval(xhrObj.responseText); }; xhrObj.open('GET', 'A.js', true); xhrObj.send(''); http://stevesouders.com/cuzillion/?ex=10009

17. XHR Injection var xhrObj = getXHRObject(); xhrObj.onreadystatechange = function() { if ( xhrObj.readyState != 4 ) return; var se=document.createElement('script'); document.getElementsByTagName('head') [0].appendChild(se); se.text = xhrObj.responseText; }; xhrObj.open('GET', 'A.js', true); xhrObj.send(''); script must have same domain as main page http://stevesouders.com/cuzillion/?ex=10015

18. Script in Iframe <iframe src='A.html' width=0 height=0 frameborder=0 id=frame1> iframe must have same domain as main page must refactor script: // access iframe from main page window.frames[0].createNewDiv(); // access main page from iframe parent.document.createElement('div'); http://stevesouders.com/cuzillion/?ex=10012

19. Script DOM Element var se = document.createElement('script'); se.src = 'http://anydomain.com/A.js'; document.getElementsByTagName('head') [0].appendChild(se); script and main page domains can differ no need to refactor JavaScript http://stevesouders.com/cuzillion/?ex=10010

20. Script Defer only supported in IE (just landed in FF 3.1) script and main page domains can differ no need to refactor JavaScript http://stevesouders.com/cuzillion/?ex=10013

21. document.write Script Tag document.write("<scr" + "ipt type='text/javascript' src='A.js'>" + " "); parallelization only works in IE parallel downloads for scripts, nothing else all document.write s must be in same script block http://stevesouders.com/cuzillion/?ex=10014

22. Browser Busy Indicators

23. status bar progress bar logocursor block render block onload normal Script Src FFIE,FF FFIE,FF XHR Eval no XHR Injection no Script in Iframe IE,FFFFIE,FFFFnoIE,FF Script DOM Element FF noFF Script Defer FF IE,FF document.write Script Tag FFIE,FF FFIE,FF good to show busy indicators when the user needs feedback bad when downloading in the background

24. Ensure scripts execute in order: necessary when scripts have dependencies IE: http://stevesouders.com/cuzillion/?ex=10017 http://stevesouders.com/cuzillion/?ex=10017 FF: http://stevesouders.com/cuzillion/?ex=10018 http://stevesouders.com/cuzillion/?ex=10018 Avoid scripts executing in order: faster – first script back is executed immediately http://stevesouders.com/cuzillion/?ex=10019 Ensure/Avoid Ordered Execution

25. Summary of Traits || down- loads domains can differ existing scripts browser busy ensures order size (bytes) normal Script Src noyes IE,FF ~50 XHR Eval IE,FFno ~500 XHR Injection IE,FFnoyesno ~500 Script in Iframe IE,FFno IE,FFno~50 Script DOM Element IE,FFyes FF ~200 Script Defer IEyes IE,FFIE~50 document.write Script Tag IE * yes IE,FFIE~100 * Only other document.write scripts are downloaded in parallel (in the same script block).

26. and the winner is... XHR Eval XHR Injection Script in iframe Script DOM Element Script Defer Script DOM Element Script Defer Script DOM Element Script DOM Element (FF) Script Defer (IE) XHR Eval XHR Injection Script in iframe Script DOM Element (IE) XHR Injection XHR Eval Script DOM Element (IE) Managed XHR Injection Managed XHR Eval Script DOM Element Managed XHR Injection Managed XHR Eval Script DOM Element (FF) Script Defer (IE) Managed XHR Eval Managed XHR Injection Script DOM Element (FF) Script Defer (IE) Managed XHR Eval Managed XHR Injection different domains same domains no order preserve orderno order no busy show busy no busy preserve order

27. Load Scripts without Blocking don't let scripts block other downloads you can still control execution order, busy indicators, and onload event

28. Inline Scripts Block long executing inline scripts block rendering and downloads http://stevesouders.com/cuzillion/?ex=10035 workarounds: initiate execution with setTimeout (>250 for FF, nglayout.initialpaint.delay ) move JavaScript to external script with advanced downloading techniques use Defer attribute (IE only)

29. Inline Scripts after Stylesheets Block Downloading Firefox 3 and IE download stylesheets in parallel...unless the stylesheet is followed by an inline script http://stevesouders.com/cuzillion/?ex=10021 best to move inline scripts above stylesheets or below other resources use Link, not @import

30. eBay MSN MySpace Wikipedia Examples of Scattered Scripts

31. Don't Scatter Inline Scripts remember inline scripts carry a cost avoid long-executing inline scripts don't put inline scripts between stylesheets and other resources

32. Get Satisfaction Widget

33. Loading...... function gsfn_populate(id, template) { document.getElementById(id).innerHTML = template; }

34. good –small improve –add future Expires header – widgets.js, favicon.gif (not topics.widget) –gzip – wigets.js, topics.widget –minify widgets.js –remove ETags –use only one: getsatisfaction.com or www.getsatisfaction.com www.getsatisfaction.com –load scripts async 3 requests 8K xfer size 8K JS (uncompr)

35. Google Calendar Widget

36. <iframe_ src="//www.google.com/calendar/embed ?mode=AGENDA &height=600 &wkst=1 &bgcolor=%23FFFFFF &src=v9ke3029e8k53qjtbf506jumu8ktapjh%40im port.calendar.google.com &color=%235A6986 &ctz=America%2FLos_Angeles" style=" border-width:0 " width="800" height="600" frameborder="0" scrolling="no">

37. good –gzip turned on –no ETags –future Expires headers improve –big! 135K JS, 18K CSS (uncompressed) –set iframe SRC dynamically –44% of JS unused –sprite 6 images into 1 –/feeds/ is slow (only 2K, but longer than 133K JS) 10 requests 65K xfer size 135K JS (uncompr)

38. Google Friend Connect Widget

39. var skin = {}; skin['HEIGHT'] = '150'; skin['HEADER_FOOTER_BG_COLOR'] = '#BFEECC'; skin['MEMBERS_LIST_BG_COLOR'] = '#D9FFE4'; skin['MEMBERS_LIST_FRIEND_LINK_COLOR'] = '#339966'; skin['MEMBERS_LIST_HEADER_FONT_COLOR'] = '#339966'; skin['INVITE_LINK_COLOR'] = '#339966'; google.friendconnect.container.renderMembersGadget( { id: 'div-08054659623916314855-members', site: '08054659623916314855' }, skin);

40. 39 requests 188K xfer size 471K JS (uncompr) (3 widgets)

41. good –gzip turned on –no ETags –future Expires headers improve –big! (really 3 widgets) –3 redirects – max-age=0 –74% of JS unused –22 requests expire in 24 hours –173K of images – lossless compression cuts 87% –4 text/html responses not gzipped (total 19K) –6 CSS expressions –3 duplicate scripts – iframes 39 requests 188K xfer size 471K JS (uncompr) (3 widgets)

42. MyBlogLog Widget

43. var mbl_widget = ''; mbl_widget += ''; mbl_widget += ' a.mbl_widget {…}'; mbl_widget += ' a.mbl_widget_u {…}'; mbl_widget += ' a.mbl_widget_a {…}'; mbl_widget += ''; [321 lines later...] mbl_widget += ' '; document.write(mbl_widget);

44. js 14 requests 60K xfer size 62K JS (uncompr) good –sprite (v3_1_default_black.gif) –domain sharding –images optimized improve –add future Expires (nopic_48.gif, close12_1.gif) –5 DNS lookups –avoid document.write –80% of JS unused –load script asynchronously

45. Plaxo Widget

46. iframe is appended to div

47. good –10 day future Expires –gzip enabled –domain sharding (Flickr) –backend stitching improve –/badge is slow – start with previous request –do away with iframe altogether – one script –load script asynchronously – set size of div –4 images could be sprited into 1 js 14 requests 41K xfer size 2K JS (uncompr)

48. Announcement 1: UA Profiler tracks browser performance traits http://stevesouders.com/ua/ go to the test page your browser automatically walks through the tests (requires JS) results recorded and shared publicly currently ~3K tests, ~2K unique testers, ~120 browsers help out by running the test!

49. Measuring Performance Episodes dev boxsynthetic testing bucket testing real user data Hammerhead

50. Announcement 2: Hammerhead "moving performance testing upstream" http://stevesouders.com/hammerhead/ Firebug extension load M URLs N times, empty & primed cache record average & median time add'l features: export data load time measurement modal cache clearing combine with bandwidth throttler

51. Takeaways focus on the frontend run YSlow: http://developer.yahoo.com/yslow http://developer.yahoo.com/yslow this year's focus: JavaScript Split the Initial Payload Load Scripts without Blocking Don't Scatter Inline Scripts speed matters life's too short, write fast code

52. Steve Souders souders@google.com http://stevesouders.com/docs/widget-summit-2008.ppt