Designing the Firefox Performance Monitor (2): Monitoring Add-ons and Webpages

November 6, 2015 § Leave a comment

In part 1, we discussed the design of time measurement within the Firefox Performance Monitor. Despite the intuition, the Performance Monitor had neither the same set of objectives as the Gecko Profiler, nor the same set of constraints, and we ended up picking a design that was not a sampling profiler. In particular, instead of capturing performance data on stacks, the Monitor captures performance data on Groups, a notion that we have not discussed yet. In this part, we will focus on bridging the gap between our low-level instrumentation and actual add-ons and webpages, as may be seen by the user.

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Designing the Firefox Performance Stats Monitor, part 1: Measuring time without killing battery or performance

October 27, 2015 § Leave a comment

For a few versions, Firefox Nightly has been monitoring the performance of add-ons, thanks to the Performance Stats API. While we are waiting for the greenlight to let it graduate to Firefox Aurora, as well as investigating a few lingering false-positives, and while v2 is approaching steadily, it is time for a brain dump on this toolbox and its design.

The initial objective of this monitor is to be able to flag both add-ons and webpages that cause noticeable slowdowns, so as to let users disable/close whatever is making their use of Firefox miserable. We also envision more advanced uses that could let us find out if features of webpages cause slowdowns on specific OS/hardware combinations.

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What have I done since last July?

July 16, 2015 § Leave a comment

School year 2014-2015 is ending. It’s time for a brief report.

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Living in a Go Faster, post-XUL world

July 13, 2015 § 31 Comments

A long time ago, XUL was an extraordinary component of Firefox. It meant that front-end and add-on developers could deliver user interfaces in a single, mostly-declarative, language, and see them adapt automatically to the look and feel of each OS. Ten years later, XUL has become a burden: most of its features have been ported to HTML5, often with slightly different semantics – which makes Gecko needlessly complex – and nobody understands XUL – which makes contributions harder than they should be. So, we have reached a stage at which we basically agree that, in a not-too-distant future, Firefox should not rely upon XUL anymore.

But wait, it’s not the only thing that needs to change. We also want to support piecewise updates for Firefox. We want Firefox to start fast. We want the UI to remain responsive. We want to keep supporting add-ons. Oh, and we want contributors, too. And we don’t want to lose internationalization.

Mmmh… and perhaps we don’t want to restart Firefox from bare Gecko.

All of the above are worthy objectives, but getting them all will require some careful thought.

So I’d like to put together a list of all our requirements, against which we could evaluate potential solutions, re-architectures, etc. for the front-end:


  • Get rid of the deprecated (XUL) bits of Gecko in a finite time.
  • Don’t break Firefox [1].

User-oriented goals

  • Firefox should start fast.
  • The UI should not suffer from jank.
  • The UI should not cause jank.
  • Look and feel like a native app, even with add-ons.
  • Keep supporting internationalization.
  • Keep supporting lightweight themes.
  • Keep supporting acccessibility.

Contributor/dev-oriented goals

  • Use technologies that the world understands.
  • Use technologies that are useful to add-on authors.
  • Support piece-wise, restart-less front-end updates.
  • Provide an add-ons API that won’t break.
  • Code most of the front-end with the add-ons API.

[1] I have heard this claim contested. Some apparently suggest that we should actually break Firefox and base all our XUL-less, Go Faster initiatives on a clean slate from e.g. Browser.html or Servo. If you wish to defend this, please step forward :)

Does this sound like a correct list for all of you?

Re-dreaming Firefox (3): Identities

June 5, 2015 § 8 Comments

Gerv’s recent post on the Jeeves Test got me thinking of the Firefox of my dreams. So I decided to write down a few ideas on how I would like to experience the web. Today: Identities. Let me emphasise that the features described in this blog post do not exist.

Sacha has a Facebook account, plus two Gmail accounts and one Microsoft Live identity. Sacha is also present on Twitter, both with a personal account, and as the current owner of his company’s account. Sacha also has an account on his bank, another one on Paypal, and one on Amazon. With any browser other than Firefox, Sacha’s online life would be a bit complicated.

For one thing, Sacha is logged to several of these accounts most of the time. Sacha has been told that this makes him easy to track, not just when he’s on Facebook, but also when he visits blogs, or news sites, or even shopping sites, but really, who has time to log off from any account? With any other browser, or with an older version of Firefox, Sacha would have no online privacy. Fortunately, Sacha is using Firefox, which has grown pretty good at handling identities.

Indeed, Firefox knows the difference between Facebook’s (and Google’s, etc.) main sites, for which Sacha may need to be logged, and the tracking devices installed on other sites through ads, or through the Like button (and Google +1, etc.), which are pure nuisances. So, even when Sacha is logged on Facebook, his identity remains hidden from the tracking devices. To put it differently, Sacha is logged to Facebook only on Facebook tabs, and only while he’s using Facebook in these tabs. And since Sacha has two GMail accounts, his logging on each account doesn’t interact with the other account. This feature is good not only for privacy, but also for security, as it considerably mitigates the danger of Cross-Site Scripting attacks. Conversely, if a third-party website uses Facebook as an identity provider, Firefox can detect this automatically, and handle the log-in.

Privacy doesn’t stop there. Firefox has a database of Terms of Service for most websites. Whenever Firefox detects that Sacha is entering his e-mail address, or his phone number, or his physical address, Firefox can tell Sacha if he’s signing up for spam or telemarketing – and take measures to avoid it. If Sacha is signing up for spam, Firefox can automatically create an e-mail alias specific to this website, valid either for a few days, or forever. If Sacha has a provider of phone aliases, Firefox can similarly create a phone alias specific to the website, valid either for a few days, or forever. Similarly, if Sacha’s bank offers temporary credit card numbers, Firefox can automatically create a single-transaction credit card number.

Firefox offers an Identity Panel (if we release this feature, it will, of course, be called Persona) that lets Sacha find out exactly which site is linked to which identity, and grant or revoke authorizations to log-in automatically when visiting such sites, as well as log in or out from a single place. In effect, this behaves as a Internet-wide Single Sign On across identities. With a little help, Firefox can even be taught about lesser known identity providers, such as Sacha’s company’s Single Sign On, and handle them from the same panel. That Identity Panel also keeps track of e-mail aliases, and can be used to revoke spam- and telemarketing-inducing aliases in just two clicks.

Also, security has improved a lot. Firefox can automatically generate strong passwords – it even has a database of sites which accept accept passphrases, or are restricted to 8 characters, etc. Firefox can also detect when Sacha uses the same password on two unrelated sites, and explain him why this is a bad idea. Since Firefox can safely and securely share passwords with other devices and back them up into the cloud, or to encrypted QR Codes that Sacha can safely keep in his wallet, Sacha doesn’t even need to see passwords. Since Firefox handles the passwords, it can download every day a list of websites that are known to have been hacked, and use it to change passwords semi-automatically if necessary.

Security doesn’t stop there. The Identity Panel knows not only about passwords and identity providers, but also about the kind of information that Sacha has provided to each website. This includes Sacha’s e-mail address and physical address, Sacha’s phone number, and also Sacha’s credit card number. So when Firefox finds out that a website to which Sacha subscribes has been hacked, Sacha is informed immediately of the risks. This extends to less material information, such as Sacha’s personal blog of vacation pictures, which Sacha needs to check immediately to find out whether they have been defaced.

What now?

I would like to browse with this Firefox. Would you?

Re-dreaming Firefox (2): Beyond Bookmarks

June 3, 2015 § 17 Comments

Gerv’s recent post on the Jeeves Test got me thinking of the Firefox of my dreams. So I decided to write down a few ideas on how I would like to experience the web. Today: Beyond Bookmarks. Let me emphasize that the features described in this blog post do not exist.

« Look, here is an interesting website. I want to read that content (or watch that video, or play that game), just not immediately. » So, what am I going to do to remember that I wish to read it later:

  1. Bookmark it?
  2. Save it to disk?
  3. Pocket it?
  4. Remember that I saw it and find it in my history later?
  5. Remember that I saw it and find it in my Awesome Bar later?
  6. Hope that it shows up in the New Tab page?
  7. Open a tab?
  8. Install the Open Web App for that website?
  9. Open a tab and put that tab in a tab group?

Wow, that’s 9 ways of fulfilling the same task. Having so many ways of doing the same thing is not a very good sign, so let’s see if we can find a way to unify a few of these abstractions into something more generic and powerful.

Bookmarking is saving is reading later

What are the differences between Bookmarking and Saving?

  1. Bookmarking keeps a URL, while Saving keeps a snapshot.
  2. Bookmarks can be used only from within the browser, while Saved files can be used only from without.

Merging these two features is actually quite easy. Let’s introduce a new button, the Awesome Bookmarks which will serve as a replacement for both the Bookmark button and Save As.

  • Clicking on the Awesome Bookmarks icon saves both the URL to the internal database and a snapshot to the Downloads directory (also accessible through the Downloads menu).
  • Opening an Awesome Bookmark, whether from the browser or from the OS both lead the user to (by default) the live version of the page, or (if the computer is not connected) to the snapshot.
  • Whenever visiting a page that has an Awesome Bookmark, the Awesome Bookmark icon changes color to offer the user the ability to switch between the live version or the snapshot.
  • The same page can be Awesome Bookmarked several times, offering the ability to switch between several snapshots.

By switching to Awesome Bookmarks, we have merged Saving, Bookmarking and the Read it Later list of Pocket. Actually, since Firefox already offers Sync and Social Sharing, we have just merged all the features of Pocket.

So we have removed collapsed items from our list into one.

Bookmarks are history are tiles

What are the differences between Bookmarks and History?

  1. History is recorded automatically, while Bookmarks need to be recorded manually.
  2. History is eventually forgotten, while Bookmarks are not.
  3. Bookmarks can be put in folders, History cannot.

Let’s keep doing almost that, but without segregating the views. Let us introduce a new view, the Awesome Pages, which will serve as a replacement for both Bookmarks Menu and the History Menu.

This view shows a grid of thumbnails of visited pages, iOS/Android/Firefox OS style.

  • first the pages visited most often during the past few hours (with the option of scrolling for all the pages visited during the past few hours);
  • then the Awesome Bookmarks (because, after all, the user has decided to mark these pages)/Awesome Bookmarks folders (with the option of scrolling for more favourites);
  • then, if the user has opted in for suggestions, a set of Awesome Suggested Tiles (with the option of scrolling for more suggestions);
  • then the pages visited the most often today (with the option of scrolling for the other pages visited today);
  • then the pages visited most often this week (with the option of scrolling for the other pages visited this week);

By default, clicking on an Awesome Bookmark (or history entry, or suggested page, etc.) for a page that is already opened switches to that page. Non-bookmarked pages can be turned into Awesome Bookmarks trivially, by starring them or putting them into folders.

An Awesome Bar at the top of this Awesome Pages lets users quickly search for pages and folders. This is the same Awesome Bar that is already at the top of tabs in today’s Firefox, just with the full-screen Awesome Pages replacing the current drop-down menu.

Oh, and by the way, this Awesome Pages is actually our new New Tab page.

By switching to the Awesome Pages, we have merged:

  • the history menu;
  • the bookmarks menu;
  • the new tab page;
  • the awesome bar.

Bookmarks are tabs are apps

What are the differences between Bookmarks and Tabs?

  1. Clicking on a bookmark opens the page by loading it, while clicking on a tab opens the page by switching to it.

That’s not much of a difference, is it?

So let’s make a few more changes to our UX:

  • Awesome Bookmarks record the state of the page, in the style of Session Restore, so clicking on an Awesome Bookmark actually restores that page, whenever possible, instead of reloading it;
  • The ribbon on top of the browser, which traditionally contains tabs, is actually a simplified display of the Awesome Pages, which shows, by default, the pages most often visited during the past few hours;
  • Whether clicking on a ribbon item switches to a page or restores it is an implementation detail, which depends on whether the browser has decided that unloading a page was a good idea for memory/CPU/battery usage;
  • Replace Panorama with the Awesome Page, without further change.

So, with a little imagination (and, I’ll admit, a little hand-waving), we have merged tabs and bookmarks. Interestingly, we have done that by moving to an Apps-like model, in which whether an application is loaded or not is for the OS to decide, rather than the user.

By the way, what are the differences between Tabs and Open Web Apps?

  1. Apps can be killed by the OS, while Tabs cannot.
  2. Apps are visible to the OS, while Tabs appear in the browser only.

Well, if we decide that Apps are just Bookmarks, since Bookmarks have been made visible to the OS in section 1., and since Bookmarks have just been merged with Tabs which have just been made killable by the browser, we have our Apps model.

We have just removed three more items from our list.

What’s left?

We are down to one higher-level abstraction (the Awesome Bookmark) and one view of it (the Awesome Page). Of course, if this is eventually released, we are certainly going to call both Persona.

This new Firefox is quite different from today’s Firefox. Actually, it looks much more like Firefox OS, which may be a good thing. While I realize that many of the details are handwavy (e.g. how do you open the same page twice simultaneously?), I believe that someone smarter than me can do great things with this preliminary exploration.

I would like to try that Firefox. Would you?

Re-dreaming Firefox (1): Firefox Agents

May 29, 2015 § 9 Comments

Gerv’s recent post on the Jeeves Test got me thinking of the Firefox of my dreams. So I decided to write down a few ideas on how I would like to experience the web. Today: Firefox Agents. Let me emphasise that the features described in this blog post do not exist.

Marcel uses Firefox every day, for quite a number of things.

  • He uses Firefox for fun, for watching videos and playing online games. For this purpose, he has installed a few tools for finding and downloading videos. Also, one of his main search engines is YouTube. Suggested movies? Sure, as long as they are fun.
  • He uses Firefox for social networks. He follows his friends, he searches on Facebook, or Twitter, or Google+. If anything looks fun, or useful, he’d like to be informed.
  • He uses Firefox for managing his bank accounts, his taxes, his health insurance. For this purpose, he has paranoid security settings – to avoid phishing, he can only browse to a few whitelisted websites – and no add-ons. He may be interested in getting information from these few websites, and in security updates, but that’s about it. Also, since Firefox handles all his passwords, it must itself be protected by a password.
  • He uses Firefox to read his Gmail account. And to read his other Gmail account. And he doesn’t want to leak privacy information by doing so on the same Firefox that he’s using for browsing.
  • Oh, and he may also be using Firefox for browsing websites that are sensitive for any kind of reason, whether he’s hunting for gifts for his close family, dating online, chatting with hackers, discussing politics, helping NGOs in sensitive parts of the globe, visiting BitTorrent trackers, consulting a physician through some online service, or, well, anything else that requires privacy. He’d like to perform such browsing with additional anonymity guarantees. This also means locking Firefox with a password.
  • Sometimes, his children or friends borrow his computer and use Firefox, too.

Of course, since Marcel brings his own device at (or from) work, that’s the same Firefox that he’s using for all of these tasks, and he’s probably even doing several of these tasks at the same time.

So, Marcel has a set of contradictory requirements, not to mention that each of his uses of Firefox needs to pass a distinct Jeeves Test. How do we keep him happy nevertheless?

Introducing Firefox Agents

In the rest of this post, I will be calling each of these uses of Firefox an Agent (if we ever implement this feature, it will, of course, be called Persona). Each Agent matches one way you use Firefox. While Firefox may be delivered with a predefined set of Agents, users can easily create new Agents. In the example, Marcel has his “Fun Agent”, his “Social Agent”, his “Work Agent”, etc.

Each Agent is unique and separate:

  • Each Agent has its own icon on Marcel’s menu/desktop/tablet/phone and task list.
  • Each Agent has its own visual identity, to make sure that work-related stuff doesn’t end up accidentally in the Fun Agent.
  • Each Agent has its own set of preferences, bookmarks, remembered passwords, cookies, cache, and add-ons.
  • Each website may be connected to a given Agent, so that links received through Gmail or through Thunderbird, for instance, automatically open with the right Agent.

As a consequence, any technology that can come bundled with Firefox to, for instance, provide search suggestions or any other kind of website suggestions is tied to an Agent. For instance, Marcel’s browsing a dating site, or shopping for shoes, or having religious activities will not be visible to any of his colleagues looking above his shoulder at his Work Agent, nor will it be tied to either of Marcel’s Gmail accounts. This greatly increases the chances of suggestion technologies passing the Jeeves Test.

Agents are also connected:

  • A menu in each Agent, as well as a keyboard shortcut, lets users quickly open/switch to other Agents.
  • When an Agent follows a link to a website that belongs to another Agent, the relevant Agent opens automatically.
  • Bookmarks may be pushed, on demand, from one Agent to another one.
  • Passwords may be pulled, on demand, from one Agent to another one.

How far are we from Agents?

Technologically speaking, Firefox Agents almost exist. Indeed, Firefox has supported Profiles forever, since way before Firefox 1.0. I generally have three instances of Firefox opened at the same time (four when I’m doing web development), and it works nicely.

With a few add-ons, you can get almost everything, although not entirely connected together:

  • Profilist helps a lot with switching between profiles, and the dev version adds distinct icons;
  • Firefox Themes implement distinct appearances;
  • there are add-ons implementing whitelist browsing;
  • there are add-ons implementing password-protected Firefox.

A few features are missing, but as you can see, the list is actually quite short:

  • Pushing/pulling passwords and bookmarks between Agents (although that’s a subset of what Firefox Accounts can do).
  • Attaching specific websites to specific Agents (although this doesn’t seem too difficult to implement).
  • Connecting this all together.

What now?

I would like to browse with this Firefox. Would you?

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