Adblock Plus:
Working on a successful extension

Wladimir Palant

Some facts on Adblock Plus

• Main purpose: blocking ads
• First release in January 2006
• Successor to the Adblock extension
• Most popular extension on addons.mozilla.org
• More than 5 million daily active users

Inner workings

• Hard work is done by the browser: content policies
• Decides, what should be blocked - filters
• Assists the user in filter creation and management
• Updates filter lists automatically

How does an extension get popular?

• I don't really know, only guessing
• Good idea
• Usable implementation
• Involving community
• Luck
• Wrong way: write once, update never

Why community?

• Somebody needs to spread the word
• Many more points of view
• Share responsibilities
• You won't stay with the project forever

Getting community feedback (1)

• Addons.mozilla.org reviews
  • Require registration
  • Not supposed to be used for feedback
  • No notifications about new reviews
  • No way to get more information from user
• Bugzilla
  • Requires registration
  • Confusing
  • E-mail address visible to everybody
  • Encourages one-to-one communication

Getting community feedback (2)

• Mailing list
  • Requires subscribing
  • E-mail address visible to everybody
• Blog
  • Good for introducing upcoming changes
  • Can be used to get community opinion
  • Not suitable for longer discussions

Getting community feedback (3)

• E-mail
  • One-on-one communication
  • Shows a face behind the project, more personal
  • High pressure to answer
• Forum
  • Registration can be made optional
  • Participation is easy
  • Perfect for end-user support
  • Hard to filter out valid bug reports

Developing in the open

• Source code is open - but only few will look at it
• Clean up and document code, encourage participation
• Announcements for new features
• Open discussion about changes
• Publish useful development milestones
  • Early feedback
  • Testing of new functionality

Filtering feedback

• Everybody has an opinion
• A loud opinion isn't necessarily a good opinion
• Most participants in discussions are technically savvy, not representative
• Important questions:
  • How many users will benefit from this improvement?
  • Which new problems or inconsistencies are introduced?
  • How much development time is required?
  • What is the maintaining cost of the feature?
• Keep an eye on support questions

User interface design for masses

• Early adopters like choice
• Average users hate having to choose
• Finding the right balance is hard
• Delegating decisions to users is not a good strategy
• Sane defaults are crucial, extension needs work out of the box
• Commonly required options should be easy to find

Options dialog example (1)

Options dialog example (2)

Providing localizations (1)

• People like extensions in their native language
• Make sure extension can be fully translated
  • Use DTD files and string bundle for all language-sensitive information
  • No language-dependent information in icons
  • Don't forget that other languages have different grammar (multiple plural forms, different word order, complex conjugation)
• Make the work easier for localizers
  • String freeze

Providing localizations (2) - babelzilla.org

Dealing with Mozilla bugs

• New Firefox version only comes out once a year
• Still, work-arounds shouldn't be permanent
• Report bugs as early as possible (use nightly builds)
• Getting bugs fixed requires some effort
  • Make sure it is a bug
  • Create a minimized testcase
  • Provide detailed steps to reproduce
  • Find a regression range
  • Locate the cause of the bug
  • Test potential fixes

Security

• Most extension authors never have to deal with security issues
• When security vulnerabilities are published, it is bad both for the extension and Firefox
• Security issues should always be highest priority and never downplayed
• It is better to prevent security issues than to fix them
• Common problem sources: displaying remote content inside a chrome document (RSS readers), not validating data received from a web page, flawed update mechanisms

Questions?