This document discusses evaluating the performance of third-party scripts on websites. It begins by defining third-party scripts as anything served to the client from an external organization, not the website itself. Common types are then listed, with Google scripts comprising 71% of the top used scripts. The document goes on to discuss issues third-party scripts can cause including negative performance impacts, creating single points of failure, and privacy concerns. Potential solutions explored are using asynchronous loading, hosted libraries, and tools to monitor and measure third-party scripts.

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3rd Party Footprint
EVALUATING THE PERFORMANCE OF EXTERNAL SCRIPTS
BARBARA BERMES /bbinto

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3rd Party Footprint
EVALUATING THE PERFORMANCE OF EXTERNAL SCRIPTS
BARBARA BERMES /bbinto

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I live in Toronto, Canada

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I love burritos

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I’m passionate about
web perf

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Let’s get this 3rd party started!

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In the strictest sense, anything served to
the client that’s provided by an
organization that’s not the website
provider is considered to be third-party
“
”–Ben Vinegar, Author of “Third-Party Script”
What is a 3rd party script?

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Types of 3rd party scripts
Advertising
Tracking and Analytics
Fonts
Social Media
Libraries and Frameworks

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What’s the #1 used
3rd Party script?

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Stats from Big Query

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AKAMAI (FB)
14%
TWITTER
5%
FACEBOOK
10%
GOOGLE
71%
Top 10

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Visualize the impact of
3rd party scripts

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Foreign content overload

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Example: Wired
• Body Level One
• Body Level Two
• Body Level Three
• Body Level Four
• Body Level Five

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But what’s the issue?

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The Issues and Negative Impacts
Performance
Front-end Single Point of Failure (SPOF)
Privacy

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Potential Solutions
Safe Snippets
Caching and Hosted Libraries
Tools and Initiatives

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Performance

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- John Hjelmstad
Google I/O 2012 (How we Make JavaScript Widgets Scream)
The value you get out of the widget needs to be
greater than the performance hit you are taking
Rule of Thumb

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A user who has to endure an 8-second download delay
spends only 1% of their total viewing time looking at the featured
promotional space on a landing page.
In contrast, a user who receives instantaneous page rendering
spends 20% of viewing time within the promotional area
(source: Jakob Nielsen)
“
”
Perception of promotional space

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A website without ads?

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The performance impact of ads
• Body Level One
• Body Level Two
• Body Level Three
• Body Level Four
• Body Level Five

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40%
Using no (client-side) ad code reduced
CBC’s page load time by 40%
<script/>

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Monitor foreign
content, constantly!

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ArithmeticMeanins
0
2.5
5
7.5
10
10/4/12 10/31/12
Bad 3rd parties (CBC mobile Site)
Smooth sailing
Client-side Ads
Ads turned off
Server-side Ads
Source: Keynote Daily Reports
We noticed a spike

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Single point of failure

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A single point of failure (SPOF) is a part of a
system that, if it fails, will stop the entire system
from working
–Wikipedia
SPOF

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The Offender
It will block rendering anything after this line

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Yeah…whatever
3rd providers don’t really go down…

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Oh yes, they do!

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Title Text
Title Text

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The Great Firewall of China

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Simulating SPOF
on TechCrunch

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SPOF-O-Matic

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SPOF WIRED
Without SPOF
With SPOF: Visually complete 40s

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Let’s crash this party

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Title Text
Title Text
#webrebels

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Initializing
client-side scripts

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Safest (previous) way:
Dynamic script tag (to cover most of the browsers)

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http://www.phpied.com/social-button-bffs/
Asynchronous Loading

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Title Text
Asynchronous Loading

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Title Text
Asynchronous Loading

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Title Text
Asynchronous Loading

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Title Text
Asynchronous Loading

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Title Text
Asynchronous Loading

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Title Text
Asynchronous Loading

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Before

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5 seconds 25 seconds
#webrebels

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After

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AFTER
5 seconds
#webrebels

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The Future

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Async or Defer JS

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Async or Defer JS

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Async and Defer JS

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Protect yourself with the help of tools
Ad-hoc browser tools
Continuous integration and deployment tools

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Caching?
Don’t always rely on it!

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30min
3 min
Cache Policies
20 min
30 min
1 hr
20 min

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What about hosted libraries?

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Pages using Google CDN
(Top Alexa Websites)
0%
0.25%
0.5%
Jan '11 Jan '13 Jan '13 Jan '14 Jan '15
11%
17%
26%
37%
47%
Percentage
Google Hosted Libraries
PAGES USING GOOGLE
LIBRARIES API
52%
48%

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Anywhere?
Don’t just copy and paste

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SPOF Alert!

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Don’t do this….

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Rather do this: Silent Fail

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Source: May 2015, Big Query result on jQuery from Google CDNs
Google’s hostest jQuery fragmentation
OTHER
30%
1.4.2
5%1.11.0
6%1.8.2
6%
1.11.1
7%
1.9.1
8%
1.8.3
8%
1.10.2
8%
1.7.1
10%
1.7.2
12%

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So, whats the verdict:
Hosted Libraries or not?

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Privacy

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Title Texthttps://developers.facebook.com/docs/plugins/like-button/

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Title Text
What they don’t really tell you that they maybe….
track the visited website, your IP, and more….????
Did you agree to that?

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Open Source Initiatives
and Resources

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Privacy Hero heise’s
Opt-in Solution

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Measuring 3rd party content on your site
Navigation Timing API
Resource Timing API

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0
120
240
Jan '14 Feb '14 Mar '14 Apr '14 May '14 Jun '14 Jul '14 May '15
82 86 86
99
130
157
168
232
Fastly Optimizely
Instagram Cedexis Twitter TypeKit
CDNPlanet Walmart Tumblr Disqus
Adoption of Timing-Allow-Origin
Header (Top Alexa Websites)

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Title Text
jsmanners

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Title Text
https://github.com/triblondon/
Contribute on Github!

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Next time before
you copy and paste

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• Refuse 3rd party content that doesn’t provide async
options or is not minified
• Put the risk in the SLA (uptime etc.)
• Review jsmanners
• Educate other (junior) developers
• Test it via navigation and resource timing where applicable
What to do as a Publisher & Developer

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• Ask for server-side options
• Evaluate tag managers
• Investigate hosted libraries (if no own CDN is available)
• Monitor, monitor, ….and monitor
• Evaluate the need of the script with marketing and
sales
What to do as a Publisher & Developer

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What to do as a Script Provider
• Provide non-blocking code samples and snippets
• Educate developers, and verify the integration of
your script (proof-check)

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The Party’s Over
Thank you

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Questions?
bit.ly/webrebels
Shameless Plug: I wrote a book
“Lean Websites” (SitePoint)
Release: end of May 2015