Best viewed with...

Best viewed with... - Adam Onishi

  • the "Browser War" is bigger than ever, with more major players
  • end up with a bad situation where you have a feature that many browsers are missing
  • developer-first development?
    • pick the latest and greatest just for fun
  • progressive enhancement
  • "vague, but exciting"
  • make fewer assumptions, focus on the user's tasks and goals
  • control
    • once it's down the network it's out of our control
  • progressive enhancement ~ defensive enhancement
  • what do we know?
    • at least one request was successful
  • baseline
    • we send them one file, a starting point from which to enhance
    • performance
    • first render within a single file
  • perceived performance
    • make it feel much quicker than it actually is

Progressively enhanced performance

Render blocking content


  • you have to download it
  • must parse the whole cascade before it can start to render
  • is still an enhancement
  • critical path CSS
    • a small amount inline in the head
    • async the rest with JS
  • tooling
    • addyosmanni/critical
    • filamentgroup/loadCSS


  • some browsers wait for full font download before rendering text
  • async font loading available for TypeKit now
  • font loading API
    • giving control to the developer
    • choice of timeouts
    • choose to show text or not before font is downloaded
    • browser support is "alright"
  • CSS font rendering spec draft


  • "1.1% of people aren't getting JavaScript enhancements (1 in 93)"
  • not always needed, what reason do you have for your content to rely on JS
  • is there a better way?
    • universal JavaScript (isomorphic)
    • rendering with a Node.js server
  • React
    • React.renderToString() - doesn't require a DOM
  • Ember's fastboot (not yet production ready)
  • checkout GoCardless' splash pages
  • this gives us back control

The network

  • assumption
    • you don't have to have access to the web to get online
  • Service Worker
    • web vs native
    • parts of the web will be offline
    • can cache things for performance
    • Development flow
      • important to know how to refresh your service worker
    • https only
    • how much can I cache?
      • as much as the browser will let you
      • browser can clean it up as and when it pleases


Is it the return of the browser wars? Well no, not really. Use progressive enhancements to only do things when they're supported.