Workshop: Getting up to speed

Wiki google doc

shell command traceroute to see the network llayers

set http connection to KeepAlive: On

HTTP hints

Can be in headers, html attributes, or dynamic JS

ex <link rel="preload" href="">

These are more useful for dynamically injected assets or assets below the fold of the page.

  • preload DNS, TCP, SSL & HTTP Request. (perfect for fonts) (current page)
  • prefetch DNS, TCP, SSL & HTTP Request. (to prefetch the next page) (next page)
  • dns-prefetch DNS only (current page)
  • preconnect DNS, TCP, SSL (can be combined with dns-prefetch)(current page)


CSS is render-blocking to avoid FOUC. It is possible to add a media attribute (print, media queries) to the <link>.

Critical Path CSS Render

  • load critical css inlined and minimized in the (determine it programatically critical-path-css-tools by Addy Osmani) aim for < 14kb so it transfers on the first trip in the HTTP request.
  • load the rest of the css dynamically with JS loadCSS. Set a cookie to flag that the css is already loaded.


JS is parsing blocking. <script> has the attribute async (downloads JS without parting) and defer (the same as async but waits to execute until DOM is ready).

Hidden Chrome dev tools experiment



  • Fires that piece of code when the browser is idle.
  • perfect for analytics events like Mixpanel


font-display to tell the browser how to treat your font loading.

  • auto
  • fallback
  • block
  • swap
  • optional

Use rel="preload" and crossorigin +

Variable fonts

  • has all the weights baked into one file


You can select the subset of the font that you need. Discard glyphs that you dont use like accents for other languages.

Subsetting can be done in the href as a query string param for example &text=Hello

Prefer woff2. Load: local(), woff2, or woff (in that order)

You can use unicode-range in @font-face to load specific subset of unicode ranges.

Audit tools

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