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Measuring Web Performance: Metrics & Tools
Michael Geers
March 25, 2017
Technology
2
350
Measuring Web Performance: Metrics & Tools
The talk was presented on JSUnconf.eu 2017 in Hamburg
Michael Geers
March 25, 2017
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Transcript
MEASURING WEB PERFORMANCE Michael Geers @naltatis JSUnconf.eu 2017
WHY MEASURE?
WHAT TO MEASURE?
PAGE RESOURCES
PAGE WEIGHT • Transferred data • Slow connectivity • Metered
contracts • Optimisation • Reduce assets • Minify JS & CSS • Active gzip Chrome DevTools
# REQUESTS • Number of assets • Browser only uses
8 parallel requests per domain • Optimisation • Domain sharding • Bundling & spriting • HTTP/2
CACHABILITY • Local browser cache • Reuse already loaded assets
• Optimisations • expires / max-age header with asset-hashing • etag / last-modified
TIMINGS
• Server processing time • Browser waits for HTML •
Optimisation • Streaming templates Time to First Byte / TTFB
Page Loaded? DOMContentLoaded • Browser finished processing the HTML document
Load • All referenced assets are loaded (img, fonts, ads, tracking, …)
Custom Metrics - User Timing API window.performance .mark('sell_page_interactive')
VISUAL METRICS
• First Visual Reaction • „Critical Path“ • Optimisation •
Prioritize assets Time to First Paint https://github.com/sitespeedio/browsertime/blob/master/ browserscripts/timings/firstPaint.js
• Primary Content is Visible • above-the-fold text • e.g.
product image • „Soft metric“ Time to First Meaningful Paint https://docs.google.com/document/d/ 1BR94tJdZLsin5poeet0XoTW60M0SjvOJQttKT-JK8HI/view#heading=h.yi0gbyc627x1
• Viewport is fully rendered • Depends on screen size
Time to Visually Complete
SpeedIndex https://sites.google.com/a/webpagetest.org/docs/using-webpagetest/metrics/speed-index
SpeedIndex https://sites.google.com/a/webpagetest.org/docs/using-webpagetest/metrics/speed-index lower is better
HOW TO MEASURE?
Network Throttling Chrome DevTools | Netwerk-Tab Firefox | Responsive Design
Mode Network Link Conditioner | Hardware IO Tools for Xcode
Chrome DevTools | Timeline-Tab Low-End Device Mode
5 METRIC TOOLS
Yahoo YSlow • Calculates a score based on best practices
• Focuses on network based metrics • Recommends improvements
Google PageSpeed Insights • Analyses rendering • Critical path •
SEO relevant • Cons • Not open source (any more) • Google API-Key required • Pre-RWD • Aggressive mobile rules
WebPageTest • Father of the SpeedIndex • Solid results •
Records video • Online results • Cons • Confusing user interface • Messy selfhosting (Windows) https://www.webpagetest.org/
sitespeed.io • Docker based (selfhosting) • Visual Metrics • Modular
• Accessibility Rules • CI & Metric Integration • Cons • might contain bugs https://www.sitespeed.io/
Google Lighthouse • Chrome Extension • Command Line Tool •
Visual Metrics • First Meaningful Paint • Interaction-Metrics • Estimated Input Latency • Progressive Enhancement https://developers.google.com/web/tools/lighthouse/
GETTING REAL
Real User Monitoring • Measuring inside the users browser •
real device distribution • real browser distribution • real connectivity situations
Navigation Timing API
Resource Timing API
https://github.com/WPO-Foundation/RUM-SpeedIndex • Google project • Combines viewport & resource timing
API • Experimental RUM-SpeedIndex
boomerang.js • Collects metrics in the browser • Started by
Yahoo! <script src="boomerang/boomerang.js" /> <script> BOOMR.init({ beacon_url: "/logging" }); </script> https://github.com/SOASTA/boomerang
browsertime • Part of sitespeed.io • Leverages browser APIs https://github.com/sitespeedio/browsertime/tree/master/browserscripts/timings
No OpenSource RUM Solution :(
TIPS
Performance Budgets https://timkadlec.com/2013/01/setting-a-performance-budget/
Continuous Integration & Visualisations
Facebook 2G Tuesday • Slowdown to 2G speed for 2
hours • Opt-in dialogue the Facebook app http://www.businessinsider.com/facebook-2g-tuesdays-to-slow-employee-internet-speeds-down-2015-10?IR=T
Show don’t tell webpagetest comparison
None
Thanks for watching! Michael Geers / naltatis