Abstract Sequential Stephanie Hobson's abstract thoughts in the sequence she has them.


This article was originally published on the Mozilla Marketing Engineering & Operations blog.

We enabled HTTP/2 on MDN’s CDN.

We didn’t do anything to optimize for HTTP/2, we just enabled it.

We’re seeing performance improvements.

You don’t have to get ready before you start using HTTP/2

While doing research to see if turning it on without doing any optimizations was a good idea I read things like:

“It also means that all of those HTTP1 performance techniques are harmful. They will make a HTTP2 website slower, not faster – don’t use them.” – HTTP2 for front-end web developers


“However, many of the things you think of as being best practices can be detrimental to performance under HTTP/2.” – Getting Ready For HTTP2: A Guide For Web Designers And Developers

Which suggest that enabling HTTP/2 on a site optimized for HTTP/1.1 could result in a slower site.

A better way to interpret those quotes is:

If you optimize for HTTP/1.1 and turn on HTTP/2 your site will not be as fast as it could be – but it might still be faster!

On MDN we concatenate a lot of our files but we don’t concatenate all of them. For example, our article pages have 9 different files coming from our CDN. I thought we could benefit from a bit of HTTP/2’s multiplexing and header compression. And we did. You can see the DNS lookup time drop off in this waterfall from Pingdom:

Waterfall showing over 0.3s of DNS look up for each request.

Waterfall showing DNS lookup for only first asset requested.

Some numbers

Overall, our tests don’t show a huge improvement in page load speed but there are small improvements for everyone, and a real improvement for users located far away from our servers. (Hi Australia and China!)

Service Location Browser HTTP/1.1 HTTP/2 Change
Pingdom Dallas Chrome 1.54s 1.34s 0.2s
Pingdom Melbourne Chrome 2.94s 2.80s 0.14s
WebPageTest London IE11 2.39s 2.37s 0.02s
WebPageTest Australia Firefox 5.61s 5.17s 0.44s
Google Analytics All Chrome 3.74s 3.04s 0.7s
Google Analytics All Firefox 3.99s 3.71s 0.28s
Google Analytics Australia All 3.01s 1.69s 1.32s
Google Analytics China All 8.10s 6.69s 1.41s

I tried to segment our users in Google Analytics to make sure we did not have a negative impact on users relying on HTTP/1.1 and… I couldn’t find enough users to draw any conclusions. MDN is lucky like that. (It’s possible the IE11 test in the table above is on Windows 7 and does not support HTTP/2, but WebPageTest doesn’t identify the OS.) In theory, older browsers should not be affected because the protocol falls back to HTTP/1.1.

There was a lot of variation in the page speed data I examined. I recommend running your before and after benchmark tests multiple times on multiple days so you can take an average. Try to wait a week before drawing conclusions from your analytics data as well.

In a perfect world you don’t increase the amount of code on your site or invalidate anyone’s caches in the sample time period, but we don’t develop in a perfect world.

Read more on HTTP/2


Get our pages into data centres around the world.

This involves changing our hosting services, not a small task, and changing our pages to serve the same content to all logged out users.

Decrease asset size by removing support for older browsers.

If you think working on MDN was a great job because we have very modern browser support requirements, remember we’re also working on a 10 year old code base.

Thanks for using MDN!

Flipping More Tables

A few weeks ago I gave my talk on displaying data tables on small screens at Cascadia Fest. Which is a super awesome 3 days conference in the Pacific North West focusing on CSS and JavaScript (Browser and Server side!)

The video of my talk has been posted:

And my slides are available here.

Google Analytics, Privacy, and Event Tracking

This article was originally published on the Mozilla Hacks blog.

Many of us use Google Analytics (GA) or similar third-party services to keep track of how people interact with our websites; telling us things like when people visit and what they click. This data can help us make important decisions, such as when to schedule maintenance or if a feature can be removed.

Because these services are installed on multiple websites these third-parties can collect a lot of information about people as they move around the internet. Not everyone is comfortable with that. Some people have started taking steps to protect their privacy by installing ad blockers like Ghostery or enabling tracking protection in Firefox.

I think this is great!

Sometimes this breaks things

When code depends on these third-party services and they’re not there stuff goes wrong.

I’m going to use tracking external links as my example because it’s a common use case, but I started investigating this problem because we accidentally broke the ability to navigate within our website for users who were choosing not to load the GA script.

I’m also going to use the universal analytics tracking code (analytics.js) for my examples here, not the classic analytics code (ga.js), so if you notice some differences between my code and yours that might be why.

What goes wrong?

The current method (Jan 2016) for tracking outbound links as recommended by Google looks like this:

<a href="http://www.example.com"
   onclick="trackOutboundLink('http://www.example.com'); return false;">
        Check out example.com
var trackOutboundLink = function(url) {
    ga('send', 'event', 'outbound', 'click', url, {
        'transport': 'beacon',
        'hitCallback': function(){document.location = url;}

What Google is recommending here is:

  1. add return false to your links so that clicking on them doesn’t take the user off the page
  2. when a user clicks a link, add that click to the GA queue of events to track and tell GA to take the user to the new page after that is done
  3. GA processes the event
  4. GA triggers the callback, taking the user to the new page

This guarantees that the user doesn’t leave the site before their action is recorded. However, if GA fails to process the event… it never triggers the callback, breaking all links off the website. :(

We are relying on GA to send the user to the new page, but what if the GA code never executes?

How we can avoid problems

If you’re using the current recommended method of adding GA to your site you’re including something like this on all your pages:

(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)})(window,document,'script','//www.google-analytics.com/analytics.js','ga');

ga('create', 'UA-xxxxx-x', 'auto');
ga('send', 'pageview');

This snippet creates a global ga object. The ga object is available in JavaScript whether the rest of the script successfully loads from Google or not.

This means two things:

  1. It is possible to add events to the queue before GA has loaded. (Cool! This is handy for tracking events that happen really quickly.)
  2. We can’t check if GA has loaded by checking for the existence of the ga object like we used to because it’s always there.

So how do we know if GA has loaded? Well, clever people have figured out that when it initializes, GA alters the global ga object in a few different ways. None of these changes are officially documented by Google which means any of them could break in the long term.

In Tracking outbound links with Google Analytics, Andreas Veithen (who works at Google but was writing on his personal blog) suggests that the most reliable check is to see if the ga object still has the q array. The array is removed after GA initializes and processes all the events waiting in the ga.q queue. Because ga.q is created by the snippet we paste on our sites, changing it would require us to make changes to our websites and so would be a major change for Google to undertake. On the other hand, it would also be possible for Google to change their code to not remove ga.q so I’m not sure this is more reliable than any other method.

In Google Analytics, Ghostery, and Event Tracking John Morton suggests checking for the create property on the ga object. This technique has been around the longest and is probably the most widely used (I say this after a quick informal glance at GitHub).

In Workaround for when the hitCallback function does not receive a response (analytics.js), Dom Sammut observes that we can check for the loaded property on the ga object. This is a method used informally in some Google documentation so it’s probably also somewhat reliable. I like this one because it is obvious what we’re checking for.

Opting for the last method, we alter Google’s suggested code like so:

var trackOutboundLink = function(url) {
    // check if the GA object exists and that it has initialized
    if(window.ga && ga.loaded) { {
        // if yes, rely on GA to follow link
        ga('send', 'event', 'outbound', 'click', url, {
            'transport': 'beacon',
            'hitCallback': function(){document.location = url;}
    } else {
        // if not, follow link ourselves
        document.location = url;

Making this kind of check before relying on any third-party script is good practice. You should also be including a local fallback for any script that is not coming from your own domain – including CDNs.

Respecting our users’ privacy

Most users care about their privacy and there are more steps we can take to protect it. Depending on where you work you may also be required by your country’s laws or your company’s privacy policy to take extra care with users’ data.

Configuring Google Analytics for privacy

If Google Analytics is your analytics platform of choice, there are a number of steps you can take to make it more private.

One of these is an easy configuration option to request anonymized user IP addresses. Essentially, Google Analytics changes the last octet of the user’s IP address to 0 before recording it.

This is triggered by adding an additional line to your tracking snippet after ga('send', 'pageview');.

ga('set', 'anonymizeIp', true);

Of course, Google still gets the users’ IP address (that’s the way the web works), we’re just trusting them not to store it.

Respecting Do Not Track (DNT)

It’s also possible to detect when a user has enabled Do Not Track and be pro-active about what scripts you choose to load.

Schalk Neethling documents the process in Respect User Choice ~ Do Not Track. In a nutshell, we wrap the GA call with a check to see if the user has enabled DNT before executing the call to include the file.

function _dntEnabled() { 
    // include the helper function from https://github.com/schalkneethling/dnt-helper/blob/master/js/dnt-helper.js

// Check the value of DNT before including GA
if (!_dntEnabled()) {
    // include the Google Analytics snippet

This means that the ga object will not be added to the global scope for our page, but that’s okay, the code snippet above handles that case gracefully as well.

Do you have other techniques/suggestions for using analytics services while respecting the online privacy of visitors to your site? Feel free to share your experience.

Flipping Tables

I was very pleased to be invited back to Style and Class to give a talk about making data tables responsive. Style and Class is a great Vancouver meetup I can’t recommend enough.

Here are my slides, though the video and animated gifs don’t play :(

Flipping Tables: Displaying Data on Small Screens from Stephanie Hobson

Download the slides.

And the links I encouraged everyone to check out:

(Still) Making Websites Better for Everyone

In the next few weeks I’ll be speaking at JavaScript Open Day Calgary, View Source, and JavaScript Open Day Toronto giving an updated version of Web Accessibility: 
Making Websites Better for Everyone.

Edit: videos have been posted for View Source and JavaScript Open Day Toronto. I’m more on the ball for View Source but the JSOpenDay one has some demos.

In my talk I encourage people to try out different assistive technologies themselves:

Here are two demo pages that list server status for a fictional hosting company, you should compare the bad example to the good example with one of the technology options listed above.

And here are all the resources I mention in my talk:

Conference Debrief: An Event Apart Austin 2015

Last week, because working at Mozilla is awesome, I got to attend An Event Apart Austin, the conference put on by the A List Apart organization. It’s consistently one of the highest quality conferences for front-end/user experience talks. I try to go every other year.

The conference was great and the organizers did a good job making the speakers accessible, sitting them with us at lunch and keeping them around for the mixer. The caliber of the attendees is also consistently high. I have great conversations no matter who I sit with at lunch.

Most of these speakers are pros who have done their talks in multiple places so its usually possible to find videos of them online with a bit of Googling, and they might be speaking at a conference near you!

Conference overview

Designing for performance and designing with empathy were common themes this year and we got good overviews of some exciting CSS and HTML features that will be widely supported in the near future.

My Favourite Talk

A CSS geek at heart I enjoyed Jen Simmons’ “Modern Layouts: Getting Out of Our Ruts” the most. “We’re about to see a renaissance in design on the web,” she promised at one point and I, for one, will be excited to see more than rectangles on the web. She covered CSS Shapes, Regions, Grid Layout, and the new view-port units, illustrating wonderfully with some really unique examples of layout from *gasp* print which she advocated we translate (not transfer) to the web. A similar version of this talk online if I’ve piqued your interest.

Talk Summaries

Jeffrey Zeldman
The Fault, Dear Brutus (or: Career Advice From a Cranky Old Man)
Zeldman made a compelling argument for quitting your job regularly :P He had some anecdotes about how it is the easiest path to career advancement, and this resonated with my own experience. He said the same could be accomplished by switching teams within an organization and I am glad we have so much sideways movement at Mozilla.

Yesenia Perez-Cruz
Design Decisions Through the Lens of Performance
Yesenia made a clear case for designers needing to take a lot of responsibility for the performance of a website. Designers make decisions about some of the things that add the most weight to our pages: fonts, images, and functionality – before developers ever see them. She said performance budgets should be set and understood as part of the requirements process and designers can be educated to stay within them and enlisted to help communicate with clients about staying within them as well. Great talk +1 would watch again.

Cameron Moll
Unified UX
Cameron talked about how a brand’s presence covers more screens than just a desktop and said we should be unifying user experience across browsers, devices, apps, and accounts citing the fact that 40% of all online US users start an activity on one screen and finish on another. He said we should pay attention to form and function (making widgets look and work similarly, respecting our users mental models) and data symmetry (syncing shopping carts, reading places, etc).

Karen McGrane
Content in a Zombie Apocalypse
Like Cameron spoke about the need for a unified UX, Karen spoke about the need for unified content – as much for the organization’s benefit as the users’. She encouraged us to find ways to create and update content in one place to share across all platforms. She despaired about how poor a tool a WYSIWYG editor is at translating styling decisions into semantic information (It’s not a list of links floated to the right with a narrow max width – it’s a table of contents!) and hoped for a future with better tools for storing and updating structured text so content doesn’t have to be redesigned every time a site is.

Ethan Marcotte
Laziness in the Time of Responsive Design
Ethan, who invented the term responsive web design, encouraged us to avoid the f-word for our sites – frameworks – and encouraged us to solve problems in context, watching to see where content needs adjustments rather than blanket redesigning the experience at different sizes. And he didn’t miss the opportunity to tell us hamburger menus are still awful.

Lara Hogan
Designing for Performance
Where Yesenia talked about process improvements for better performance Lara talked about code improvements. She talked in-depth about image compression, font sub-setting (explaining how the infamous 4 and a horse stars review bug occurred), style guides and OOCSS, and ended talking about setting a public performance budget and how to make performance everyone’s concern rather than having performance cops.

Eric Meyer
Designing for Crisis
Based on his personal experience sitting in a stranger’s car barrelling down a highway, racing the med-evac helicopter carrying his young daughter to a hospital in an unfamiliar city, Eric implored us to add a new persona to our design toolbox: a user in crisis. We like to think we’re designing for cheerful, calm, with-it users living in the home of the future but we don’t get to decide when, where, or how a user will access our sites. He gave examples of how this persona could help the banking, hospital, airline, and insurance industries. And he gave some creative solutions to help us do user testing for these scenarios including using CSS to blur the page, JavaScript to transpose letters in words, or playing the Jeopardy theme song to testers. He encouraged us not to treat these users as edge cases, because defining edge cases defines the limits of what we care about, and we should care about these users. I don’t see much potential for an MDN user to be in crisis but it’s easy to imagine a Firefox user who just lost all their data or thinks an account of theirs has been hacked could be panicking and not thinking clearly.

Brad Frost
Atomic Design
Pioneer of style guides and pattern libraries, Brad reminded us what these look like and why they are valuable and demoed his open source tool patternlab.io for helping to create and maintain them. He has a great system, you can read about it here.

Matt Haughey
Empathy Is Good Business: How Front-Line Customer Support Can Make You A Better Designer
Continuing the empathic design theme Matt encouraged us all to spend a couple hours a week doing front-line customer support and explained how Slack is set up so that all employees must do that. It gives everyone a better idea of how users are using the product and what their pain points are. Rather than having personas to refer to designers have real people they could reference. They also don’t talk down to their users or judge the feedback they give them. It’s all data that makes the product better.

Jeremy Keith
Resilience: Building a Robust Web That Lasts
Jeremy praised the flexibility of HTML and CSS and encouraged us to embrace their resilience rather than fighting the inherent variability of the systems. He reminded us that we can build systems that work for everyone with very basi functionality and then layer enhancements on top of it. At it’s heart instagram should be a bunch of <img>s and a <input type=”file”> and there’s no reason to require JavaScript to see your friend’s images or add your own. Layout, fonts, file previews, filters, are all enhancements. “If you build pages with the idea that parts other than HTML are optional, you will create a better and stronger web page.” – gov.uk

How To Debug CSS

Some quick notes and links for the talk I gave at WordCamp Vancouver about Debugging CSS.

Edit: You can now watch a recording of Debugging CSS. Spot the three projector failures!


  1. Is the HTML valid?
  2. Is the CSS valid?
  3. Is the right CSS being applied?
    1. Is what you typed being applied?
    2. Is other stuff being applied?
    3. Is what’s being applied right?
  4. Does CSS support what you’re doing?
  5. Does the browser support it?
  6. Can you isolate the problem?
  7. Ask for help


Other resources

Mobile First Is Performance First

Tonight I spoke at Vancouver Web Performance Meetup and I promised to share my slides so here they are:

Mobile First Is Performance First from Stephanie Hobson

If what you’re really after are the links, let me save you a bit of time:

Conference Debrief: Smashing Conference Whistler 2014

A few weeks ago Smashing Conference came to Whistler. This caliber of conference comes to Canada infrequently so I couldn’t not go ;)

The conference

As good as I hoped it would be. A mix of strategy and near future technology examples.

My Favourite Talk

Talk Summaries

Marcin Wichary
Good is the enemy of great: On designing, and then undesigning, a perfect link underline
200 years of typographic history was lost when we moved from printing presses to the typewriter, Marcin Took us through some of what he did in his attempt to re-create the perfect underline.His ultimate point was that it’s important to find a balance between shipping and creating good code. Perfectionism is not the right balance but we should strive to make things good and not just improve the status quo.

Susan Robertson
Style Guides: Why bother?
Susan walked us through a long list of benefits to using a style guide. Highlights included: front-end speed, consistency, and performance. Lots of good resources here: styleguides.io

Yoav Weiss
Responsive Images are Coming to a Browser Near You
I have been hearing a lot about new picture element and srcset attributes but Yoav was the first to really get me excited about them. The potential image management problems these additions could create are huge but there is a lot of potential to be really neat things with them. is a solution for providing art direction of images on different screen sizes and srcset gets added to if you just want to provide a smaller/larger version of an identical image.

Marcy Sutton
A Web for Everybody
Accessibility is easier if you build it you build it in from the start. Ask, does it work: With the keyboard only? In a screen reader? Without sound? Without colour? In high contrast mode? “This stuff is not that hard.”

Jenn Lukas
The Developer’s Ampersandwich
Things to consider when implementing type on a website: if you haven’t been given design direction you can find the type by looking at what’s popular and already in use, separate presentation from content, be aware of performance issues with web fonts, add accessible fallbacks for a icon fonts, use tools like typecast to communicate with designers about general styles rather than content specific styles.

Zach Leatherman
Better @font-face with Font Load Events
Web fonts are rendered blocking. Zach proposes a JavaScript fix which prioritizes a FOIT for icon fonts and a FOUT for content fonts. Lots of good stuff from this excellent article of his.

Stephen Hay
Easing the Pain of Designing in the Browser
We need to stop thinking about layout first, we need to start thinking about structured content first. Begin by focusing on the small screen, and then focus on type and color.

John Allsopp
The Web’s future is offline
“We can’t keep building apps with the desktop mindset of permanent, fast connectivity, where a temporary disconnection or slow service is regarded as a problem and communicated as an error.”

Dave Shea
Rolling Your Own CSS Methodology
A CSS framework is not about syntax. It’s about discipline and optimizing for people. Ideals Mobify uses when building theirs: classes for everything, no IDs, no nesting, no !important.

That was one day. It was a really long day.

Johnathan Snook
Jonathan gave a very personal talk about the development of his career overtime and the importance of empathy. It touched a lot of people, but it is difficult to summarize in two sentences.

Brad Frost
Atomic Design
If we all use the same framework we all look alike. We should be building “Tiny Bootstraps, for every client.” – Dave Rupert. Brad demoed patternlab.io which is a really cool tool for breaking designs down into component parts.

Lyza D. Gardner
Soothing Web Weariness: Saving the Web by Doing as Little as Possible
Make projects smaller to begin with – increase your constraints – improve them iteratively and systematically instead of accepting complexity as the status quo.

Val Head
All the Right Moves: Putting your UIs in Motion
Animations needs to be designed with intent the same way you would design any other part of the site. Prototype animations. Test that they match your site’s style and feel fast.

Kyle Simpson
#CSS {Yawn: Yay!}
Kyle talked about some high-level concepts he’d like to see implemented in CSS templating. It was very much a talk about the next generation of CSS informed by some complex computing science principles. I can’t do it justice, his slides are here

Tim Kadlec
In Between
Like Val, Tim talked about designing animations with intent. He had lots of great examples and data.

Paul Irish
Getting to Fast
Not all pixels are created equal. Paul talked about why the first 14KB transferred are the most important to performance.

It was a great conference. I left feeling super excited about my job, which is how I always want to leave conferences :)

I also gave a ‘jam session’ talk on accessibility. They hosted it in a pub and I highly recommend pub audiences, they laugh at all your jokes! Accessibility was a theme running through all of the talks at Smashing and I am glad to see it being spoken about and incorporated into examples again I feel that, as an industry, we’ve sort of forgotten about it for a few years.

Making Websites Better for Everyone

There’s a few different versions of my talk floating around now. I’m really excited and humbled to hear that people have been making changes to the way the work in response to something I said.

The most detailed (and longest) version of my talk is available to watch on WordPress TV.

My first slide deck and links to the resources I recommend are part of an earlier blog post.

In the most recent version of my talk I used a demo of a fictional hosting company’s server status page. Follow these thinks to see the bad and good examples and I encourage you to compare the two right now using some assistive technology, or at the very least, using your nose or elbow on your mouse or trackpad.

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