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๐Ÿ‡ณ๐Ÿ‡ฑ Frontmania 2022 - Web Performance APIs

๐Ÿ‡ณ๐Ÿ‡ฑ Frontmania 2022 - Web Performanceย APIs

โ„น๏ธ Web performance APIs you (probably) didn't know existed

Responsiveness to interaction is crucial for our apps and youโ€™ve probably heard about the amazing tools we have to measure web performance. But did you know there are many performance APIs native to the Web Platform?

In this talk, weโ€™ll see how to leverage the power of some of them to reliably measure responsiveness and correctly identify culprits for bad experiences.

Matheus Albuquerque

October 04, 2022
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Transcript

  1. Hello, Frontmania โœ‹ ๐Ÿ‡ณ๐Ÿ‡ฑ WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T

    KNOW EXISTED โ€ข THE 5TH OF OCTOBER, 2022.
  2. WEB PERFORMANCE APIS YOU (PROBABLY) DIDNโ€™T KNOW EXISTED MATHEUS ALBUQUERQUE

  3. ร… Iโ€™M MATHEUS ๐Ÿ™‹ โ† @YTHECOMBINATOR ON THE WEB โ†

    SR. SOFTWARE ENGINEER @MEDALLIA โ† MENTOR @TECHLABS
  4. Disclaimers WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  5. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED #1 THE

    IDEA BEHIND THIS SESSION IS HEAVILY INSPIRED BY ZENO'S SESSION BACK IN 2016.
  6. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED #1 SESSION

    BACK IN 2016.
  7. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED #2 45

    MINUTES IS A LOT OF TIME, I KNOWโ€ฆ ๐Ÿฅฑ
  8. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED #2 LOT

    OF TIME, I KNOWโ€ฆ ๐Ÿฅฑ
  9. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED #3 ๐Ÿคฏ

    = DEEP DIVE, FURTHER DISCUSSIONS AFTER THE SESSION
  10. Why am I here? WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T

    KNOW EXISTED
  11. WEB PERFORMANCE APIS YOU (PROBABLY) DIDNโ€™T KNOW EXISTED MATHEUS ALBUQUERQUE

  12. WEB PERFORMANCE STUFF YOU ALREADY KNOW MATHEUS ALBUQUERQUE

  13. โ† HTTP/2 โ† COMPRESS JAVASCRIPT (E.G. WITH BROTLI) AND USE

    IMAGE CDNS (40โ€“80% SAVINGS) โ† OPTIMIZE THIRD-PARTIES (DEFER/REPLACE/ UPDATE THEM) โ† WORKERS TO OFF-LOAD THE MAIN THREAD YOU ALREADY KNOWโ€ฆ
  14. โ€” HTTPS://WWW.PATTERNS.DEV YOU ALREADY KNOWโ€ฆ

  15. โ€” HTTPS://WWW.PATTERNS.DEV YOU ALREADY KNOWโ€ฆ

  16. #QUESTION ๐Ÿค” We're all already doing (some of) these, right?

  17. None
  18. ร…

  19. ร… โ€”โ€‰APP DYNAMICS REPORT, LAST THREE MONTHS

  20. ร… โ€”โ€‰APP DYNAMICS REPORT, LAST THREE MONTHS

  21. ร… โ€”โ€‰APP DYNAMICS REPORT, LAST THREE MONTHS

  22. ร… FIXING WEB PERFORMANCE

  23. ร… FIXING WEB PERFORMANCE

  24. This talk presents Why am I here? Measuring Measuring (with

    the platform) Optimizing (with the platform) Why are we here? Closing thoughts
  25. This talk presents Why am I here? Measuring Measuring (with

    the platform) Optimizing (with the platform) Why are we here? Closing thoughts
  26. Measuring WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  27. #QUESTION ๐Ÿค” What does it mean to be fast?

  28. #QUESTION ๐Ÿค” What does it mean to be fast? If

    you were to summarize web performance in one metric, whatโ€™d be your pick?
  29. #QUESTION ๐Ÿค” What does it mean to be fast? If

    you were to summarize web performance in one metric, whatโ€™d be your pick? e.g. load time, responsiveness, etc.
  30. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED If you

    were to summarize web performance in one metric, whatโ€™d be your pick?
  31. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED If you

    were to summarize web performance in one metric, whatโ€™d be your pick? 1st/2nd/3rd ANSWERS โ† REACT BRUSSELS DISCOUNT CODE ๐Ÿ‡ง๐Ÿ‡ช OTHERS โ† STICKERS ๐Ÿ’…
  32. None
  33. ร…

  34. #PROTIP๐Ÿ’ก A lot of loading metrics don't capture user experience.

    We need to think about our metrics in terms of what matters.
  35. #QUOTE ๐Ÿฆ„ "My app loads in n secondsโ€ฆ" โ€”โ€‰Front-End Engineers,

    ca. 2022
  36. None
  37. #PROTIP๐Ÿ’ก Load metrics are not a single number.

  38. #QUESTION ๐Ÿค” What does it mean to be fast? If

    you were to summarize web performance in one metric, whatโ€™d be your pick?
  39. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED If you

    were to summarize web performance in one metric, whatโ€™d be your pick?
  40. MEASURING PERCEIVED LOAD SPEED HOW QUICKLY A PAGE CAN LOAD

    AND RENDER ALL OF ITS VISUAL ELEMENTS TO THE SCREEN LOAD RESPONSIVENESS HOW QUICKLY A PAGE CAN LOAD/RUN ANY REQUIRED JS IN ORDER FOR COMPONENTS TO RESPOND TO USER INTERACTION RUNTIME RESPONSIVENESS AFTER THE PAGE LOAD, HOW QUICKLY CAN THE PAGE RESPOND TO USER INTERACTION? SMOOTHNESS DO TRANSITIONS & ANIMATIONS RENDER AT A CONSISTENT FRAME RATE AND FLOW FLUIDLY?
  41. #PROTIP๐Ÿ’ก The only way to truly know how your site

    performs for your users is to actually measure its performance as those users are loading and interacting with it.
  42. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Jean-Antoine Nollet

  43. โ† THE FIRST EVER RUM EXPERIMENT IN 1746 โ† HE

    GATHERED หœ200 MONKS IN CIRCUMFERENCE, WIRED USING IRON, AND DISCHARGED A BATTERY THROUGH THE HUMAN CHAIN โ† HE WAS TESTING THE LATENCY OF AN ELECTRIC SIGNAL WITH REAL USERS JEAN-ANTOINE NOLLET
  44. #PROTIP๐Ÿ’ก Browsers now provide us with many apis to fetch

    performance metrics that help site owners make sites faster.
  45. WEB PERFORMANCE STUFF YOU ALREADY KNOW MATHEUS ALBUQUERQUE

  46. WEB PLATFORM PERF APIS I DIDNโ€™T KNOW EXISTED MATHEUS ALBUQUERQUE

  47. Measuring with the platform WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T

    KNOW EXISTED
  48. MEASUREMENT APIS GENERAL STUFF DOMHighResTimeStamp, PerformanceObserver, PAGE VISIBILITY API &

    LAYOUT INSTABILITY API PROFILING LONG TASKS API, UserAgentSpecificMemory & JS SELF- PROFILING API TIMING USER TIMING, ELEMENT TIMING. EVENT TIMING, RESOURCE TIMING, NAVIGATION TIMING & SERVER TIMING SENSORS BATTERY STATUS & NETWORK INFORMATION
  49. document.hidden; document.visibilityState; document.addEventListener("visibilitychange",() = > { if(document.visibilityState==="hidden"){ console.log("This window is

    hidden") } else{ console.log("This window is visible") } }) PAGE VISIBILITY
  50. โ† CANCEL NETWORK REQUESTS AND OTHER TIME- BASED EVENTS โ†

    FETCH INCOMPLETE MEDIA OR DOWNLOAD THE REST OF YOUR BUNDLES USING DYNAMIC IMPORTS โ† PAUSE VIDEOS AND CAROUSELS, IF THE USER IS NOT WATCHING THEM PAGE VISIBILITY
  51. โ† SUBSCRIBE TO PERFORMANCE-RELATED EVENTS โ† CALLBACKS ARE GENERALLY FIRED

    DURING IDLE PERIODS โ† YOU TELL THE OBSERVER WHAT TYPES OF ENTRIES TO LISTEN FOR PerformanceObserver
  52. const observer = new PerformanceObserver((list) = > { for (const

    entry of list.getEntries()) { console.log(entry.toJSON()); } }); observer.observe({type: 'some-entry-type'}); PerformanceObserver
  53. โ† MANY WEBSITES HAVE DOM ELEMENTS SHIFTING AROUND DUE TO

    CONTENT LOADING ASYNCHRONOUSLY โ† THIS API GIVES US A LIST OF ALL LAYOUT SHIFT EVENTS ON A PAGE LAYOUT INSTABILITY
  54. const observer = new PerformanceObserver((list) = > { const entries

    = list.getEntries(); / / Shifts that are not preceded by input events const nonInputEntries = entries.filter((entry) = > !entry.hadRecentInput); for (const entry of nonInputEntries) { console.log(entry); } }); observer.observe({type: 'layout-shift'}); LAYOUT INSTABILITY
  55. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  56. ร… LAYOUT INSTABILITY

  57. ร… LAYOUT INSTABILITY

  58. TIMING (1st ACT) USER TIMING ALLOWS YOU TO MARK POINTS

    IN TIME AND THEN MEASURE THE DURATION BETWEEN THOSE MARKS. EVENT TIMING EVENT PROCESSING TIME + TIME UNTIL THE NEXT FRAME CAN BE RENDERED. THE BASIS FOR THE FID METRIC. ELEMENT TIMING MEASURE THE RENDER TIME OF SPECIFIC ELEMENTS. THE BASIS FOR THE LCP METRIC.
  59. / / Record the time i m m ediately before

    running a task performance.mark('myTask:start'); await doMyTask(); / / Record the time i m m ediately after running a task performance.mark('myTask:end'); / / Measure the delta between the start and end of the task performance.measure('myTask', 'myTask:start', โ€˜myTask:end'); observer.observe({type: 'measure'}); USER TIMING
  60. USER TIMING

  61. USER TIMING + TOOLS โ€” "USER TIMING AND CUSTOM METRICS"

    BY STEVE SOUDERS
  62. USER TIMING + TOOLS โ€” "USER TIMING AND CUSTOM METRICS"

    BY STEVE SOUDERS
  63. โ† ALLOWS YOU TO MEASURE THE RENDER TIME OF SPECIFIC

    ELEMENTS โ† USEFUL FOR KNOWING WHEN THE LARGEST IMAGE OR TEXT BLOCK WAS PAINTED TO THE SCREEN โ† THE BASIS FOR THE LARGEST CONTENTFUL PAINT (LCP) METRIC ELEMENT TIMING
  64. <img elementtiming="hero-image" /> <p elementtiming="important-paragraph">This is text I care about.</p>

    observer.observe({type: 'element'}); ELEMENT TIMING
  65. ELEMENT TIMING + TOOLS โ€” "ELEMENT TIMING: ONE TRUE METRIC

    TO RULE THEM ALL?" BY ANDY DAVIES
  66. โ† USEFUL TO MEASURE THE EVENT PROCESSING TIME AS WELL

    AS THE TIME UNTIL THE NEXT FRAME CAN BE RENDERED โ† EXPOSES A NUMBER OF TIMESTAMPS IN THE EVENT LIFECYCLE โ† THE BASIS FOR THE FIRST INPUT DELAY METRIC EVENT TIMING
  67. const observer = new PerformanceObserver((entryList) = > { const firstInput

    = entryList.getEntries()[0]; const firstInputDelay = firstInput.processingStart - firstInput.startTime; / / Measure the time it takes to run all event handlers const firstInputProcessingTime = firstInput.processingEnd - firstInput.processingStart; / / Measure the entire duration of the event const firstInputDuration = firstInput.duration; }); observer.observe({type: 'first-input'}); EVENT TIMING
  68. MEASURE THE LATENCYโ€ฆ โ† FROM A CLICK UNTIL WE REORDER

    CONTENT ON A TABLE โ† TO DRAG A SLIDER TO FILTER SOME DATA โ† FOR A FLYOUT TO APPEAR WHEN HOVERING A MENU ITEM EVENT TIMING
  69. PROFILING LONG TASKS API REPORTS TASKS THAT TAKES LONGER THAN

    50 MS AND IT'S THE BASIS FOR TTI AND TBT METRICS JS SELF-PROFILING API PROFILE SPECIFIC COMPLEX OPERATIONS AND IDENTIFY HOT SPOTS USING A SAMPLING PROFILER UserAgentSpecificMemory DETECT MEMORY LEAKS IN APPS THAT HANDLE A HUGE VOLUME OF DATA
  70. LONG TASKS

  71. โ† REPORTS TASKS THAT TAKES LONGER THAN 50 MS โ†

    USEFUL TO TRACK WHEN THE BROWSER'S MAIN THREAD IS BLOCKED โ† THE BASIS FOR TIME TO INTERACTIVE (TTI) AND TOTAL BLOCKING TIME (TBT) METRICS LONG TASKS
  72. LONG TASKS

  73. observer.observe({type: 'longtask'}); LONG TASKS

  74. observer.observe({type: 'longtask'}); { name: "same-origin-descendant", entryType: "longtask", startTime: 1023.40999995591, duration:

    187.19000002602115, attribution: [ { name: "unknown", entryType: "taskattribution", startTime: 0, duration: 0, containerType: "iframe", containerSrc: "child.html", containerId: "", containerName: "child1" } ] }; LONG TASKS
  75. const profiler = new Profiler({ sampleInterval: 10, maxBufferSize: 10000 });

    / / Do work . . . const trace = await profiler.stop(); sendProfile(trace); JS SELF-PROFILING
  76. โ† PROFILE SPECIFIC COMPLEX OPERATIONS โ† PROFILE THIRD-PARTY SCRIPTS โ†

    COMBINE WITH OTHER EVENTS/IMPORTANT METRICS, LIKE LONG TASKS OR EVENT TIMING APIS JS SELF-PROFILING
  77. โ† MEASURES THE MEMORY USAGE AND DETECTS MEMORY LEAKS โ†

    WAITS FOR THE NEXT GC AND THEN MEASURES MEMORY IMMEDIATELY AFTER THE UNNEEDED MEMORY HAS BEEN RELEASED โ† FORCES GC IF IT DOES NOT HAPPEN FOR 20S UserAgentSpecificMemory
  78. โ† FORGETTING TO UNREGISTER AN EVENT LISTENER โ† ACCIDENTALLY CAPTURING

    OBJECTS FROM AN IFRAME โ† NOT CLOSING A WORKER โ† ACCUMULATING OBJECTS IN ARRAYS MEMORY LEAKS
  79. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  80. const obj = { a: new Array(1000), b: new Array(2000)

    }; setInterval(() = > { console.log(obj.a); }, 1000); MEMORY LEAKS
  81. performance.measureUserAgentSpecificMemory() UserAgentSpecificMemory

  82. { name: "same-origin-descendant", entryType: "longtask", startTime: 1023.40999995591, duration: 187.19000002602115, attribution:

    [ { name: "unknown", entryType: "taskattribution", startTime: 0, duration: 0, containerType: "iframe", containerSrc: "child.html", containerId: "", containerName: "child1" } ] } { bytes: 1000000, breakdown: [ { bytes: 1000000, attribution: [ { url: "https://example.com", scope: "Window", }, ], types: ["JS", "DOM"], }, { bytes: 0, attribution: [], types: [], }, ], } { "frames": [ { "name": "Profiler" }, { "column": 0, "line": 100, "name": "", "resourceId": 0 }, { "name": "set innerHTML" }, { "column": 10, "line": 10, "name": "A", "resourceId": 1 } { "column": 20, "line": 20, "name": "B", "resourceId": 1 } ], "resources": [ "https://example.com/page", "https://example.com/app.js", ], "samples": [ { "stackId": 0, "timestamp": 161.99500000476837 }, { "stackId": 2, "timestamp": 182.43499994277954 }, { "timestamp": 197.43499994277954 }, { "timestamp": 213.32999992370605 }, { "stackId": 3, "timestamp": 228.59999990463257 }, ], "stacks": [ { "frameId": 0 }, { "frameId": 2 }, { "frameId": 3 }, { "frameId": 4, "parentId": 2 } ] } LONG TASKS SELF-PROFILING USERAGENT MEMORY ๐Ÿคฏ
  83. TIMING (2nd ACT) RESOURCE TIMING RETRIEVE AND ANALYZE DETAILED NETWORK

    TIMING DATA REGARDING THE LOADING SERVER TIMING COMMUNICATE PERFORMANCE METRICS ABOUT HOW TIME IS SPENT WHILE PROCESSING THE REQUEST NAVIGATION TIMING COMPLETE TIMING INFORMATION FOR NAVIGATION OF A DOCUMENT
  84. const observer = new PerformanceObserver((list) = > { for (const

    entry of list.getEntries()) { / / If transferSize is 0, the resource was fulfilled via the cache. console.log(entry.name, entry.transferSize === 0); } }); observer.observe({type: 'resource'}); RESOURCE TIMING
  85. NAVIGATION TIMING

  86. const observer = new PerformanceObserver((list) = > { for (const

    entry of list.getEntries()) { console.log('Time to first byte', entry.responseStart); } }); observer.observe({type: 'navigation'}); NAVIGATION TIMING
  87. / / ServiceWorker startup time const workerStartupTime = entry.responseStart -

    entry.workerStart; / / Request time only (excluding redirects, DNS, and connection/TLS time) const requestTime = entry.responseStart - entry.requestStart; / / Response time only (download) const responseTime = entry.responseEnd - entry.responseStart; / / Request + response time const requestResponseTime = entry.responseEnd - entry.requestStart; NAVIGATION TIMING
  88. MEASURE ANY WORK THAT THE SERVER DOES TO COMPLETE A

    REQUEST: โ† ROUTING/AUTHENTICATING THE REQUEST โ† QUERYING DATABASES/API CALLS TO THIRD-PARTY SERVICES โ† RUNNING CONTENT THROUGH TEMPLATING SYSTEMS SERVER TIMING
  89. Server-Timing: database;dur=123;desc="Database", templating;dur=56;desc="Template processing" SERVER TIMING

  90. SERVER TIMING

  91. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  92. SENSORS BATTERY STATUS INFORMATION ABOUT THE POWER SOURCE, CHARGE LEVEL,

    AND OTHERS NETWORK INFORMATION ADAPT THE USERSโ€™ EXPERIENCE BASED ON THE QUALITY OF THEIR CONNECTION
  93. const batteryInfo = await navigator.getBattery(); batteryInfo.addEventListener("chargingchange", listener); batteryInfo.addEventListener("chargingtimechange", listener); batteryInfo.addEventListener("dischargingtimechange",

    listener); batteryInfo.addEventListener("levelchange", listener); BATTERY STATUS
  94. const networkInfo = navigator.connection; navigator.connection.addEventListener('change', onConnectionChange); NETWORK INFORMATION

  95. NETWORK INFORMATION const networkInfo effectiveType: "4g", rtt: 200, downlink: 1.65,

    saveData: false, }
  96. โ† SWITCH BETWEEN SERVING HIGH/LOW DEFINITION CONTENT BASED ON THE

    USER'S NETWORK โ† DECIDE WHETHER TO PRELOAD RESOURCES โ† DEFER UPLOADS/DOWNLOADS WHEN USERS ARE ON A SLOW CONNECTION โ† ADAPT TO SITUATIONS WHEN USERS ARE OFFLINE NETWORK INFORMATION
  97. switch (connectionType) { case "4g": return <Video src={videoSrc} />; case

    "3g": return <Image src={imageSrc.hiRes} alt={alt} />; default: return <Image src={imageSrc.lowRes} alt={alt} />; } NETWORK INFORMATION
  98. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  99. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  100. None
  101. Improving with the platform WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T

    KNOW EXISTED
  102. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Resource Hints

  103. โ† MANY PERFORMANCE OPTIMIZATIONS CAN BE MADE WHEN WE CAN

    PREDICT WHAT USERS MIGHT DO โ† RESOURCE HINTS ARE A SIMPLE BUT EFFECTIVE WAY TO ALLOW DEVELOPERS TO HELP THE BROWSER TO STAY ONE STEP AHEAD OF THE USER AND KEEP PAGES FAST RESOURCE HINTS
  104. < ! - - Preconnect - - > <link rel="preconnect"

    href="https://fonts.gstatic.com"> <link rel="preconnect" href="https://scripts.example.com"> < ! - - Preloading - - > <link rel="preload" href="https://example.com/fonts/font.woff"> < ! - - DNS Prefetch - - > <link rel="dns-prefetch" href="https://fonts.gstatic.com"> <link rel="dns-prefetch" href="https://images.example.com"> < ! - - Prefetch - - > <link rel="prefetch" href="/uploads/images/pic.png"> <link rel="prefetch" href="https://example.com/news/?page=2"> < ! - - Prerender - - > <link rel="prerender" href="https://example.com/news/?page=2"> RESOURCE HINTS
  105. < ! - - Preconnect - - > <link rel="preconnect"

    href="https://fonts.gstatic.com"> <link rel="preconnect" href="https://scripts.example.com"> < ! - - Preloading - - > <link rel="preload" href="https://example.com/fonts/font.woff"> < ! - - DNS Prefetch - - > <link rel="dns-prefetch" href="https://fonts.gstatic.com"> <link rel="dns-prefetch" href="https://images.example.com"> < ! - - Prefetch - - > <link rel="prefetch" href="/uploads/images/pic.png"> <link rel="prefetch" href="https://example.com/news/?page=2"> < ! - - Prerender - - > <link rel="prerender" href="https://example.com/news/?page=2"> RESOURCE HINTS
  106. โ† IT ALLOWS THE BROWSER TO SETUP EARLY CONNECTIONS BEFORE

    THE REQUEST IS ACTUALLY SENT TO THE SERVER. THIS INCLUDES: โ€ข TLS NEGOTIATIONS โ€ข TCP HANDSHAKES โ† ELIMINATES ROUNDTRIP LATENCY PRECONNECT
  107. 100MS 200MS 300MS 400MS 500MS 600MS 700MS HTML CSS FONT

    1 FONT 2 FONTS START LOADING FONTS RENDERED
  108. 100MS 200MS 300MS 400MS 500MS 600MS 700MS HTML CSS FONT

    1 FONT 2 FONTS START LOADING FONTS RENDERED FONT 1 FONT 2
  109. โ† DNS PREFETCH โ‡ข WARNS THE BROWSER ABOUT THE DOMAINS

    ITโ€™S GOING TO NEED TO LOOK UP โ† PREFETCH โ‡ข FETCH RESOURCES IN THE BACKGROUND AND STORE THEM IN CACHE โ† PRERENDER โ‡ข IT GOES ONE STEP FURTHER AND EXECUTES THE FILES โ€ฆAND MUCH MORE!
  110. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Priority Hints

  111. โ† INCREASE THE PRIORITY OF THE LCP IMAGE โ† LOWER

    THE PRIORITY OF ABOVE-THE-FOLD IMAGES AND PRELOADED RESOURCES โ† LOWER THE PRIORITY FOR NON-CRITICAL DATA FETCHES โ† REPRIORITIZE SCRIPTS PRIORITY HINTS
  112. < ! - - Increase the priority of the LCP

    image - - > <img src="image.jpg" fetchpriority="high" /> < ! - - Lower the priority of above-the-fold images - - > <ul class="carousel"> <img src="img/carousel-1.jpg" fetchpriority="high" /> <img src="img/carousel-2.jpg" fetchpriority="low" /> <img src="img/carousel-3.jpg" fetchpriority="low" /> </ul> < ! - - Reprioritize scripts - - > <script src="async_but_important.js" async fetchpriority="high"></script> <script src="blocking_but_unimportant.js" fetchpriority="low"></script> PRIORITY HINTS
  113. < ! - - Increase the priority of the LCP

    image - - > <img src="image.jpg" fetchpriority="high" /> < ! - - Lower the priority of above-the-fold images - - > <ul class="carousel"> <img src="img/carousel-1.jpg" fetchpriority="high" /> <img src="img/carousel-2.jpg" fetchpriority="low" /> <img src="img/carousel-3.jpg" fetchpriority="low" /> </ul> < ! - - Reprioritize scripts - - > <script src="async_but_important.js" async fetchpriority="high"></script> <script src="blocking_but_unimportant.js" fetchpriority="low"></script> PRIORITY HINTS
  114. / / Important validation data const user = await fetch("/user");

    / / Less important content data const relatedPosts = await fetch("/posts/suggested", { priority: "low" }); PRIORITY HINTS
  115. / / Important validation data const user = await fetch("/user");

    / / Less important content data const relatedPosts = await fetch("/posts/suggested", { priority: "low" }); PRIORITY HINTS
  116. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Responsive Images

  117. โ† IMAGES FOR DESKTOP AND TABLET CAN BE หœ2-4X LARGER

    THAN THE MOBILE ONES. โ† WITH srcset, THE BROWSER WON'T DOWNLOAD THE LARGER IMAGES UNLESS THEY'RE NEEDED. THAT SAVES BANDWIDTH. RESPONSIVE IMAGES
  118. <img src="frontmania.png" srcset=" frontmania-300.png 300w, frontmania-600.png 600w, frontmania-1200.png 1200w "

    /> <img src="frontmania.png" srcset=" frontmania-1x.png 1x, frontmania-2x.png 2x, frontmania-3x.png 3x " /> RESPONSIVE IMAGES
  119. RESPONSIVE IMAGES <img src="frontmania.png" srcset=" frontmania-300.png 300w, frontmania-600.png 600w, frontmania-1200.png

    1200w " /> <img src="frontmania.png" srcset=" frontmania-1x.png 1x, frontmania-2x.png 2x, frontmania-3x.png 3x " />
  120. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Native Lazy-

    Loading
  121. NATIVE LAZY-LOADING <img src="image.png" loading="lazy" alt="โ€ฆ" width="200" height="200"> <iframe src="https://example.com"

    loading="lazy" width="600" height="400"></iframe>
  122. <img src="image.png" loading="lazy" alt="โ€ฆ" width="200" height="200"> <iframe src="https://example.com" loading="lazy" width="600"

    height="400"></iframe> NATIVE LAZY-LOADING
  123. #PROTIP ๐Ÿ’ก Lazy-loading iframes can lead to 2-3% median data

    savings, 1-2% FCP reductions, and 2% FID improvements at the 95th percentile. โ€”โ€‰Chrome teamโ€™s research, 2019
  124. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Native Scheduler

  125. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  126. scheduler.postTask() SCHEDULE AND CONTROL PRIORITIZING TASKS. scheduler.wait() YIELD AND RESUME

    AFTER SOME AMOUNT OF TIME OR PERHAPS AFTER AN EVENT HAS OCCURRED. scheduler.yield() BREAK UP LONG TASKS BY YIELDING TO THE BROWSER AND CONTINUING AFTER BEING RESCHEDULED. isInputPending() DETERMINE IF THE CURRENT TASK IS BLOCKING INPUT EVENTS. NATIVE SCHEDULER
  127. NATIVE SCHEDULER

  128. None
  129. โ† CSS TRICKS (E.G. font-display: swap AND will-change) โ† IMPORT

    ON VISIBILITY (USING AN IntersectionObserver) โ† CANVAS + WORKERS = OffscreenCanvas โ€ฆAND MUCH MORE!
  130. โ† AVOID THE INITIAL HTTP TO HTTPS REDIRECTS SO THAT

    PAGES LOAD FASTER USING HTTP STRICT TRANSPORT SECURITY (HSTS) โ† SEND DATA WITHOUT EXTRA ROUND TRIPS WITH QUIC โ€ฆAND MUCH MORE!
  131. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  132. SERVICES & OSS

  133. #PROTIP ๐Ÿ’ก Start with observability services or libraries like web-vitals.

    Then create your own abstractions on top of the web (e.g. React hooks).
  134. Move Fast & Break Nothing โ„ข WEB PERFORMANCE APIS YOU

    (PROBABLY) DIDN'T KNOW EXISTED
  135. BROWSER COMPATIBILITY PERFORMANCE OBSERVER USER TIMING LONG TASKS ELEMENT TIMING

    RESOURCE TIMING NAVIGATION TIMING
  136. BROWSER COMPATIBILITY SERVER TIMING LAYOUT INSTABILITY JS SELF-PROFILING PAGE VISIBILITY

    BATTERY STATUS NETWORK INFORMATION
  137. None
  138. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  139. const Video = lazy(() = > import("./Video")); const Preview =

    lazy(() = > import("./Preview")); const networkInfo = useNetworkStatus(); const { With, Switch, Otherwise } = usePatternMatch(networkInfo); MOVE FAST & BREAK NOTHING โ„ข
  140. <Suspense fallback={<div>Loading . . . </div>}> <With unsupported> <NetworkStatus networkInfo="unsupported"

    /> <Video /> </With> <With effectiveConnectionType="2g"> <NetworkStatus networkInfo="2g" /> <Preview /> </With> </Suspense> MOVE FAST & BREAK NOTHING โ„ข
  141. None
  142. None
  143. None
  144. None
  145. None
  146. Why are we here? WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T

    KNOW EXISTED
  147. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Browsers

  148. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Which browsers

    are visiting our app? โ€”โ€‰APP DYNAMICS REPORT, LAST THREE MONTHS
  149. BROWSER TOTAL

  150. None
  151. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Devices &

    Connection
  152. #REALITYCHECK ๐Ÿ˜ณ Phone users experience slow First Input Delay on

    7x more websites. โ€”โ€‰Web Almanac By HTTP Archive, 2021
  153. BANDWIDTH MIX โ€”โ€‰GSM ASSOCIATION, 2022

  154. 6.07 (MBPS) 44.31 (MBPS) โ€”โ€‰THE STATE OF LTE BY OPEN

    SIGNAL, 2018 THE GLOBAL LTE PICTURE
  155. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED People

  156. THE TIME IT TAKES TO LOAD A PAGE HOW EASY

    IT IS TO FIND WHAT I'M LOOKING FOR HOW WELL THE SITE FITS MY SCREEN HOW SIMPLE THE SITE IS TO USE HOW ATTRACTIVE THE SITE LOOKS โ€”โ€‰SPEED MATTERS, VOL. 3 HOW IMPORTANT IS SPEED?
  157. #RESEARCH ๐Ÿ“š 40% of Brits reported that they had become

    physically violent toward their computers. โ€”โ€‰British Psychology Society, 2009
  158. #RESEARCH ๐Ÿ“š A 500ms delay resulted in up to a

    26% increase in frustration and up to an 8% decrease in engagement. โ€”โ€‰Radware research, 2013
  159. #RESEARCH ๐Ÿ“š Delayed web pages caused a 38% rise in

    mobile users' heart rates โ€” equivalent to the anxiety of watching a horror movie alone. โ€”โ€‰Ericsson ConsumerLab neuro research, 2015
  160. #RESEARCH ๐Ÿ“š 53% of mobile users abandon sites that take

    over 3 seconds to load. โ€”โ€‰DoubleClick, 2020
  161. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Business

  162. โ† LONG TASKS DELAYED TTI โ† AS FIRST-PAGE LONG TASK

    TIME INCREASED, OVERALL CONVERSION RATES DECREASED โ† MOBILE HAD UP TO หœ12X LONGER LONG TASKS โ† OLDER DEVICES COULD BE SPENDING HALF OF THEIR LOAD-TIME ON LONG TASKS BUSINESS OUTCOMES โ€”โ€‰AKAMAI AND CHROME RESEARCH, 2017
  163. BUSINESS OUTCOMES โ€”โ€‰AKAMAI AND CHROME RESEARCH, 2017

  164. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED Closing Notes

  165. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED ALWAYS TRY

    TO CORRELATE BUSINESS METRICS WITH PERFORMANCE. #1
  166. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED DON'T TAKE

    FAST NETWORKS, CPUS AND RAM FOR GRANTED. #2
  167. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED TEST ON

    REAL PHONES AND NETWORKS. #3
  168. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED AVOID THE

    OBSERVER EFFECT. #4
  169. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED GET RID

    OF THE NOISE IN YOUR METRICS. #5
  170. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED THERE'S NO

    SILVER BULLET. IDENTIFY YOUR CORE METRICS. #6
  171. Weโ€™re hiring! ๐Ÿ—บ Mostly inโ€ฆ ๐Ÿ‡บ๐Ÿ‡ธ๐Ÿ‡ฒ๐Ÿ‡ฝ๐Ÿ‡ฆ๐Ÿ‡ท๐Ÿ‡บ๐Ÿ‡พ๐Ÿ‡ช๐Ÿ‡ธ๐Ÿ‡จ๐Ÿ‡ฟ๐Ÿ‡ฎ๐Ÿ‡ฑ๐Ÿ‡ฎ๐Ÿ‡ณ

  172. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  173. WEB PERFORMANCE APIS YOU (PROBABLY) DIDN'T KNOW EXISTED

  174. ร…

  175. THATโ€™S ALL, FOLKS! THANKS! QUESTIONS? MATHEUS ALBUQUERQUE