Khan Academy

Topic Badges For Great Justice!

Wed, 23 May 2012 20:45:14 -0400

Hi there, i’m marcos ojeda, a designer at Khan Academy. Let me tell you about Topic Badges.

A while back, Ben and Jason started work on revamping our exercise framework to allow multiple exercises to be grouped under the umbrella of a Topic. Jason asked me if i’d be interested in making some badges for these new higher-level topics and i eagerly agreed.

The task is pretty amazing when you first hear it: “make some icons that represent math topics like ‘addition and subtraction’ or ‘functions.’” I immediately turned to some of my favorite representational gotos, namely isotypes, Japanese Mon and Brian Eno. And naturally there’s a whole history of people trying to synthesize a concept into a single icon, so prehistoric cave painter, i tip my hat to you.

Starting points

For my attempt, i basically started doodling until a workable concept began to ossify. The standard i set for myself was something between the golden record

whose goal was to be a sort of message in a bottle to far-off lifeforms. The cover, shown above, is a sort of puzzle-explanation which, when decoded, explain how to use a cartridge (included!), as well as showing the location of earth. All without words. An explanation of the record shows exactly how much information is embedded within it.

Additionally, i took as inspiration the sorts of reference diagrams you tend to find in pre-war textbooks

for example, this book cover shows a concise representation of the Munsell color system whose core units are hue, chroma and value.

Additionally, i love the genre of “this coincidentally heraldic diagram represents everything about this course” that you tend to find in math and science classes, like this classic one which sneaks in a fixed point combinator alongside a supremely visual description of recursion:

or this gem from the back of Strang’s linear algebra textbook

whose true intention and significance only really makes sense towards the end of your first linear algebra course.

The common thread between all of these is that the symbol itself is grokkable, you can get it as a thing, but its true meaning is somewhat opaque until you understand enough of the subject for the icon to represent the relevant salient details. Since we are in the business of helping folks learn concepts, it seemed right to have badges which became more interesting the more you learned.

Topic badges

As it happens, here’s what ended up happening for, addition and subtraction exercises (q.v. the addition and subtraction topic page).

Notice that it spans the gamut between visual puns representing addition and subtraction to literal visual representations of dots being grouped and so forth.

For a topic like exponents (which isn’t yet available), you end up getting the more out of the box style treatments that begin to have that sense of mystery to them (some of them even making no direct connection to exponents at all.)

The not-so-obvious-to-me lesson here, is that sometimes trying to distill a topic will fail if the topic is too broadly specified. This is also, exactly why things like the noun project succeed at things like sasquatch but do less stellar with things like blog.

Go back and take a look at the visual solutions for Addition and Subtraction, a topic that is incredibly broad, and contrast that with the sorts of visual treatment for Exponents. As a secondary check, i think, if it becomes difficult to distill a topic without resorting to using its dominant operators, then the topic is probably too broadly specified (maybe we should have an addition topic? or grouping? who knows!)

All the badges

The result of all this topic-level navel-gazing was, at present count, 45 separate badges (of which only 28 are currently deployed):

and at a glance, all the badges here:

For each topic, there’s a regular badge and then there’s a completed badge which is rendered as a gloriously shiny button or token.

Some technical details

Despite the fact that this seems like a straightforward doodling project, there were some technical issues to deal with:

the round badge shape was not predestined, for quite a while i assumed we would crop the square to a circle using css rounded corners as a lo-fi mask, but for various reasons it eventually made sense to actually generate circular images
i am using illustrator’s artboards liberally
illustrator files don’t play nicely with most code review systems or git/hg/whatever and make it difficult to get code reviews.

Round files are a delicious curse

Illustrator files (namely their artboards) are transparent. When exporting (or saving for web) you have the option to mark the artboard as transparent, which would make round pngs trivial, right?

Lamentably, save for web is a sort of painful mouse-heavy rigamarole and if you’re trying to batch-export a bunch of badges at, say, a new size, i would rather not be on the hook for clicking over and over again. (would you?)

To that end, i wrote a small script to control graphicsmagick with ghostscript to render illustrator files at arbitrary resolution. How? It turns out illustrator files are almost entirely pdf files but with extra information for storing illustrator metadata.

Artboards are great!!

Since CS4, artboards in Illustrator are the best feature. Remember how i mentioned that illustrator files are basically pdfs in hiding? You can leverage this in order to both save divergent copies of a given illustration in the same file and also to share this information with others.

Artboards in illustrator are represented as pdf pages with their own dimensions, so this makes it trivial to share illustrator files once people know to open them with a pdf-compatible application and comment on a given page.

This also means that the first illustrator rendering script can be amended to know about artboards and what they contain. So the file has evolved somewhat to include this functionality. There’s a json file which marks which artboards are for what purpose and somebody without illustrator could actually pull down the repo and generate badges if they felt like it.

But what about code reviews?

It’s no fun to do work but not get any good feedback. You can get stuck in a rut and it’s always good to have a separate pair of eyes, but unless you want to be a hovering art director, the process of providing crit for files which are clearly works in progress is a bit awkward.

In order to get around this, I used the Mac FSEvents python library to watch over my project folder and commit the whole directory each time I hit save from within illustrator. The script which does this also lives in kiln and is called artboard.py. The result, though is that instead of obtuse commit messages, it provides some context of what changed from commit to commit.

and more interestingly, since i can have the script render on each save as well, i can take advantage of kiln’s visual diff tools, so that i actually can get valuable feedback on a given changeset or just share some changes with anyone who’s interested.

There are a bunch of small hacks between the different rendering scripts to improve edge rasterization with transparency (involving some absurd downsampling) and to create fast previews depending on what the image is for. The tangible result ends up being that it was possible to open up the design and production process to be both flexible and open.

Final points!

I know many people have reservations about using Illustrator for icon design when it gets rendered down to a tiny image. Fair enough, but also, there’s something to be said for balance benefit and cost. For now it’s an acceptable loss, but it would be nice if vector artwork could be hinted like typefaces are. In some ways, a consistent badge family shares lots of the same design properties a typeface does, so maybe type design is a better way to go about thinking about things like…

i did not obey whatever golden rule that says that the smallest stroke in an icon should be 1/20th the width of the icon’s bounding box, but i should have, because it would have made them all uniformly legible.

It was a great process and I look forward to tuning, revising and creating new badges as we work to refine the size and design of our topics this summer. Thanks for making it this far!

Share your Khan Academy badges on Facebook in style

Mon, 14 May 2012 20:19:00 -0400

As of today, you can now share your Khan Academy badges on Facebook using the new Open Graph protocol. In normal speak, it means that you’ll get richer, more interesting displays of your badges on Facebook if you choose to share them, like so:

So, how does it work?

Say your name is Mary Littlelamb, and you earn a couple of badges:

If you click on the “Share” button,

This dialog will pop up asking for you to grant us permission to post on your behalf. In order to share the badge on Facebook, you must click “Allow”. Otherwise, we can’t share it. =(

After a short delay (hopefully not too long; we have to wait for Facebook to confirm that the publish action went through), the badge will appear in your Facebook Timeline!

If you miss the opportunity to share from a badge notification dialog, you can also share from the “Recently Completed Activity” section of your Khan Academy profile page.

Just hover over the badge you want to share, and the same share links will appear in gray:

After sharing several badges, a neat Khan Academy “Badges earned” section will appear in your Facebook timeline:

You can edit or remove this view.

If you’ve shared more badges than can fit in the display case, you can customize which ones get shown by clicking on “View Individual Stories”.

On the resulting page, you can change the settings for individual badges.

Here, Mary wants to make sure “Addition and subtraction” shows up in her Timeline.

Back on Mary’s Timeline, we can see the changes were put into effect. Woohoo!

At the end of it all, Mary’s friends will be able to see her activity in their Facebook Newsfeed. Way to go, Mary!

If you click on a badge, you’ll end up at a page more info about what it takes to earn the badge, as well as a ginormous list of all the badges you can earn on Khan Academy.

Happy sharing!

Stephanie, Desmond, and Marcos

Trying out new features

Mon, 07 May 2012 15:25:00 -0400

Developer Tom Yedwab writes here about using “A/B” testing to compare the effectiveness of changes we make to the site.

“Data is easy to collect but hard to interpret, never giving you a clear result that confirms your hypotheses. However, even noisy and confusing data is invaluable in forming and testing hypotheses about user behavior.”

Our most recent tests were for our new “Watch” menu:

and our new “topic pages”:

We hope the menu and new pages are making it easier for you to find great videos!

Khan Academy and 23andMe

Wed, 02 May 2012 13:02:12 -0400

To celebrate DNA Day (April 20), Khan Academy and 23andMe partnered together to make the 23andMe video series Human Prehistory 101 and Genetics 101 available on Khan Academy.

DNA Day commemorates the day in 1953 when James Watson, Francis Crick, and colleagues published papers in the journal Nature on the structure of DNA.

Press release from 23andMe

Collaboration with MIT+K12

Wed, 25 Apr 2012 07:01:06 -0400

We are excited to announce our collaboration with MIT to develop more videos on science and engineering projects. Through a new initiative called MIT+K12, MIT students have produced videos focused on hands-on projects, simulations and historic experiments.

A selection of these videos are showcased on the MIT+K12 playlist. Videos include

- A Crash Course on Indoor Flying Robots

- The Invention of the Battery

- The Forces on an Airplane

- Flocculation: Making Clean Water

- A Voyage to Mars: Bone Loss in Space

- Bread Mold Kills Bacteria

- Bouncing Droplets

More information on the MIT+K12 initiative can be found in this press release. Let us know what you think!

Happy Easter from Khan Academy

Sun, 08 Apr 2012 12:04:00 -0400

from designer Kitt Hirasaki:

Learn more about pysanky, Ukranian Easter Eggs!

Show and Tell: Hovercards

Wed, 04 Apr 2012 21:25:14 -0400

From developer Marcia Lee:

about a week ago, we released hovercards (not to be confused with hoverboards). the next time you watch a video on ka, mouse over the name of someone who has posted a comment, question, or answer!

the observant ka user will recognize that hovercards are mini versions of a user’s public profile, with her avatar, name, five hand-picked badges, and some stats hinting towards her commitment to the site.

discussing a video on ka is intellectually fruitful, and the hope is that hovercards make the experience more joyful and more human. human in that you can imagine the other people who also mulled over which five badges to share, who also played around with their arrangement until their display case looked just right, and who are embarking on educational journeys that cross paths with your own.

give it a try and let us know how you feel!

check out more screenshots chronicling this feature’s development.

Khan Academy and the Google Art Project

Tue, 03 Apr 2012 10:01:00 -0400

From Khan Academy Co-Deans for Art and History, Beth Harris and Steven Zucker:

You may have been wondering what Smarthistory has been up to since we joined Khan Academy in October. We’ve had to keep this hush-hush…but we can now announce that we have contributed more than 100 videos to the unbelievably great, second iteration of the Google Art Project:

We’ve made 90 Khan Academy videos expressly for version 2, which launched today, April 3rd, at the Musée d’Orsay, the Art Institute of Chicago, and museums in many other countries. We’ve also contributed 26 pre-existing videos to the Art Project. Finally, we worked closely with Sandbox Studios to create an engaging introduction to looking at art:

Our videos can be seen in the education section (the playlist is embedded at the bottom of the first page) and on the specific object “detail” pages.

We jumped at this opportunity because the Art Project has such enormous educational potential. It is critical to gather works of art from different institutions to tell the nuanced stories of art history. The Art Project brings together works of art from 151 museums in 40 countries within a cohesive visual environment. The high resolution images, powerful zoom function, “Museum View” (an interior version of “Street View”) and the ability to collect and annotate images, are all features that are ideal for teaching and learning.

Museums of art safeguard, make accessible, and interpret our shared cultural history even as they help to define the civic aspirations of their communities. Museums have always been defined by place, although traveling exhibitions and, more recently, museum websites have helped to “jail break” the art. André Malraux famously identified this new ability to see across institutional collections in his essay, the “Museum Without Walls.”

For a “Museum Without Walls” is coming into being, and…it will carry infinitely farther that revelation of the world of art…which the “real” museums offer us within their walls.

——André Malraux, The Voices of Silence

As always, all Smarthistory.khanacademy.org content is free and open. If you’re an art historian, museum educator, or curator, and you’re interested in contributing to the work we’re doing, please contact us.

We especially want to thank Colleen Brogan and Rachel Ropeik for coming through in a pinch and for their uncanny ability to make complex ideas clear.

You can browse our full playlist of videos for the Art Project here:

Khan Academy Labs: Exploratory Exercises

Fri, 30 Mar 2012 13:18:00 -0400

From instructor Brit Cruise:

One of the most exciting aspects of joining the Khan Academy team was the potential to explore new ways of integrating video and software. As a new faculty member, I hope to deliver mini-courses as journeys. These journeys expose a user to a chain of concepts, ultimately leading to a field of study they will be encouraged to explore!

Instead of having the user answer questions after each video, I realized it would be beneficial to have them visually explore key concepts in real-time through exploratory exercises (Brett Victor does this brilliantly). I see this as a vital analysis phase in the experience; the salient aspects are a powerful learning mechanism.

Perhaps it’s because I grew up playing Will Wright’s video games that I was never a fan of right or wrong answers. Instead, the rewards are a result of your own discoveries:

With the help of David Sissitka (one of the many awesome volunteers who kick in @ Khan Academy), I was able to deliver some initial demos within 3 days of conceiving the idea:

Do you think you can mimic a coin flip?

and:

Have you ever seen your frequency fingerprint in real-time?

Check out these first two (of many) explorations that are intended to supplement the journey into cryptography series. This is just the first step in what I hope will be a long and exciting experiment in education:

Understanding Topic Mastery with Bayesian Networks

Wed, 28 Mar 2012 13:50:12 -0400

Jace Kohlmeier is the scientist studying our statistics to figure out how Khan Academy users learn best.

He’s working to answer questions like:

What are the underlying concepts that relate mastery of our hundreds of exercises to each other?
Can we predict the best ordering of topic for a user to minimize time spent and maximize success?
What instructional interventions can an intelligent learning system make to best aid the user?

To learn about the software behind answering these questions, check out Jace’s new post about building Bayesian networks in Python for Khan Academy.

Changing learning habits at Oakland Unity

Tue, 27 Mar 2012 01:51:00 -0400

Oakland Unity, a charter school located on the east side of Oakland, has been piloting Khan Academy this year by using a rotational learning lab model. On a recent test on systems of equations, the class average was double what it was last year, and a deeper dive into the data shows even more promise.

While they’ve seen impressive academic gains, the math teachers have started seeing something potentially more profound: students have been gaining confidence, putting more effort into their work, and taking responsibility over their own learning. According to Peter McIntosh, the Algebra teacher at Oakland Unity:

When we stopped worrying about whether Khan Academy videos were better than our own lectures or whether the exercises had the appropriate mix of concept vs. drill, we recognized that we had found a powerful tool that reached students and changed their habits in ways we had never even considered possible.

Read more about Oakland Unity’s academic gains and changes in students’ habits in this blog post. And in Oakland Unity’s second blog post, you can see how this change has impacted individual students.

David tells the story of his internship at Khan Academy

Thu, 05 Jan 2012 20:09:39 -0500

Fall ‘11 intern David Hu created this incredible video about his experience at Khan.

Teach ALL the Humans.

If you want to change the world like David, sign up at khanacademy.org/r/jobs

You can also read more about David’s work or the projects that were done by our previous class of Khan Academy interns.

Ready, set, subtitle!

Wed, 14 Dec 2011 14:48:29 -0500

Now if you visit www.khanacademy.org/contribute, you can pick a language, click a button and be taken to a video to subtitle! You can also filter by language and subject and select a specific video. Help educate the world. Ready, set, subtitle!

Khan Academy teaming up with Renren to bring free online education to China

Wed, 14 Dec 2011 14:40:00 -0500

With nearly 500 million Internet users, China is the largest online population in the world. Our video lessons will be hosted at khan.56.com for free by Renren Inc. (NYSE: RENN), one of China’s leading social networking internet platforms, through its online video subsidiary 56.com. We’re excited about cooperating with Renren to further expand our education model outside the United States and continue to realize our mission to makeworld-class education available for free to anyone anywhere.

Making education more accessible around the world

Mon, 12 Dec 2011 23:36:00 -0500

We often get emails from people around the world who use Khan Academy. There are now over 2.4 million visits per month coming from outside the US (hurray!). Much of this usage is from people who heard or stumbled upon our resources and just started using it for themselves. However, there are also many schools and organizations in countries such as India, Brazil, South Africa and Ghana that are experimenting and using our materials as a core element of how they educate their students.

One such organization that is using Khan Academy is the African School for Excellence (ASE), in Accra, Ghana. Despite being constrained by the limited number of computers and broadband access, the teachers at ASE incorporated Khan Academy as their Math curriculum in a 4-week pilot. What is exciting how they managed to innovate around their infrastructure constraints, and ASE’s CEO has written a thoughtful article about the creative fixes they used. ASE plans to run a few more pilots early next year in Ghana and South Africa and will continue to find new ways to work with the resources that they have available.

It is amazing to hear about how these organizations (and more that we have not even heard about) are innovating to bring world-class education to their students — especially in regions where getting basic education is a hurdle for many children. There’s a magic that happens when high quality content is available for free to the world, and it is exciting to see what happens when people are inspired to take action and change the world one step at a time.

We love hearing these stories, so if you are helping bring Khan Academy to other parts of the world — let us know by posting a comment below!

How Khan Academy is using Machine Learning to Assess Student Mastery

Wed, 02 Nov 2011 16:56:59 -0400

Khan Academy developer David Hu writes a very interesting piece about how we’re running a number of experiments to improve our understanding of student mastery and encourage more learning from our students:

In high level terms, we increased overall interest — more new exercises attempted, fewer problems done per proficiency — without lowering the bar for proficiency — P(next problem correct | just gained proficiency) was roughly the same for both groups. Further, it seemed that overall learning, as measured by the distribution of accuracies obtained, went up slightly under the new model.

Optimistically, we hypothesise that our gains are from moving students quicker off exercises they’re good at, while making them spend more time on concepts in which they need more practice.

Read more…

Khan Academy expands to Art History

Wed, 19 Oct 2011 18:42:00 -0400

Khan Academy is best known for our Math and Science content, but our goal has always been to provide a free world-class education on as many subjects as possible. However, we knew that other subjects, particularly Art and History, require a different take on how to present the topics.

We were thrilled to find Dr. Beth Harris and Dr. Steven Zucker, the creators of SmartHistory. Their style of spontaneous conversations, where speakers are not afraid to disagree and challenge each other, really resonated with us. Their videos are short, casual, approachable, interesting, and thought-provoking, and they bring many of the same sensibilities that have really resonated with our audience.

We are pleased to announce that we are joining forces. Dr. Beth Harris and Dr. Steven Zucker will join our faculty and lead the creation of Art, History, Architecture, and other content in the humanities.

They have already created over 300 videos, and you can see them all at: http://smarthistory.khanacademy.org. Over time, expect to see tighter integration of their content on http://www.khanacademy.org.

We think this is the beginning of a tremendous collaboration, and we are incredibly excited to push the frontier on freely available content in the Arts and Humanities.

Impact from using Khan Academy

Thu, 15 Sep 2011 13:30:00 -0400

by Shantanu Sinha

We received an email a couple of months ago from a young man named Mark Halberstadt. In true Khan Academy style, he recorded a YouTube video for us to watch.

His story is quite inspirational. Mark is a student who had given up on Math and Science and thought he was incapable of ever pursuing a career in a related field. He claims he was always a “C” student growing up and never had a channel to understand topics that interested him in engineering. He found the Khan Academy in 2007 and started watching videos on Trigonometry, Calculus, and even Arithmetic. He decided to go back to school last year to get a Bachelors degree in Electrical Engineering. He finished his first year in college with a 4.0 GPA for the entire year, including perfect scores on his Calculus and Chemistry final exams. He says, “coming from a background where my GPA graduating from high school was in the 2.0 range. That never would have happened — getting a 4.0 GPA would never have happened without the help I got from the Khan Academy.” He goes on to say, “It has helped me immensely. The impact for me in my life…I see it growing exponentially over the next 20 or 30 years.”

Students have always liked Khan Academy. The YouTube comments Sal received when he posted his first videos in 2006 are what motivated him to keep going (creating over 2400 as of today). However, it is still astonishing to see the impact our resources can have. Of course, while Mark is thanking us, he deserves 100% of the credit. He did all the work and took control of his own learning after the educational system left him behind. We just played a small role in enabling him.

If there were only 1 student like Mark Halberstadt in the world, it would have been worth creating Khan Academy. The fact that this could so easily scale to millions is what makes Khan Academy special.

Khan Academy seems to work well with supplemental learners like Mark, but how well does it work in schools? We have always believed that a great teacher can take our resources and push learning to new heights, by better focusing on the individual needs of each student. With the student mastering core skills on the computer, the teacher can leverage the classroom time for more engaging and dynamic activities such as project-based learning, peer tutoring, or lively discussion.

Last school year, we started piloting our platform in a few schools in Los Altos, California. Our goal was to create better tools by directly observing how teachers and students interacted with our product. Los Altos was a fantastic partner, and our team built out many significant features based on their feedback (e.g., student knowledge map, teacher dashboards, badging infrastructure, new exercises).

At the end of the school year, we all knew it was a success. Teachers could see a dramatic change in their students’ excitement and enthusiasm towards Math. Students who traditionally struggled with the material were more confident and engaged. Other students were challenging themselves to levels we never thought possible. Common sense told everyone involved that we were on to something.

We did not do a controlled research study. In part, because our organization was only 5 people for most of the school year, and we were just trying to build something worth researching. Things changed fast for us, and the system the students were using at the end of the school year was very different from the system they started using in November.

However, we were curious to see how they did on traditional assessments like the end of year CST exam. It is not the ideal exam since it only tests performance on a narrow set of grade-level skills. Many of our students were remediating topics they should have learned years ago, or challenging themselves with much more advanced topics. None of these gains would be captured. However, the CST clearly matters, so it is worth understanding how our students performed.

The initial results were quite promising. Our pilot included a couple of 7th grade classrooms with students who typically struggled in Math. We saw a significant improvement in this group. The number of Advanced or Proficient students increased dramatically, from 23% to 41%

This was very heartening. Usually, the performance gap widens with students who struggle in Math, particularly when they get to more advanced topics like Pre-algebra. The fact that these students were closing the gap (non-pilot classrooms saw no significant change in their CST performance) was very promising.

Our pilot also included a few 5th grade classrooms. Los Altos is a high performing district, and these students typically do very well on the CST. This year was no different, with 96% of the students in pilot classrooms scoring Advanced or Proficient. While these are great results, they are not statistically different from the non-pilot classrooms in the district. It turns out, in both pilot and non-pilot classrooms, the students were doing great on the exam and didn’t have much room for improvement.

However, we could see amazing things happening with the 5th graders. A majority of students were attempting early Algebra, and many students were experimenting with Trigonometry and Calculus. These students were excited, engaged, and loved being challenged. Inadvertently, we highlighted a distinct but not often discussed problem with standardized, age-focused education. Students performing at high levels are often not sufficiently challenged. Teachers shouldn’t take kids who already know the material, and make sure they already know the material. Teachers should be pushing and challenging the students to their full abilities. Los Altos didn’t think everything was perfect because their students were scoring well on standardized exams; they saw significant value in creating an environment that was engaging and challenging for all students.

Based on these experiences, Los Altos has now decided to expand the implementation district-wide to over 40 more classrooms. We are also working with a number of additional schools that represent different use cases (e.g., charter, independent, low-income, special needs) to understand how students react to our resources in these different settings. This year we will also look into a better evaluation methodology that reflects learning gains across multiple grade levels.

We are completely convinced that our resources can have a huge impact on the learning process. But why exactly does Khan Academy work? Some people have a hard time understanding how online videos and practice exercises can make such a big difference. Or they misunderstand what Khan Academy is all about.

Putting videos on YouTube is just a small piece of the equation. What Khan Academy enables is a fundamentally different way for students to approach learning. Here’s my take on the many innovations we are bundling together into a coherent experience. This is what is really making the difference.

Students are free to learn anytime, anywhere
Students can jump to where help is needed most, and spend as much time as necessary to master concepts
The content is short, fun, approachable, and easily digestible
There is a clear and continuous path to learning complex topics
Students feel an increased sense of ownership - they are learning, not “being taught”
The focus on core conceptual understanding ensures students build the necessary skills that are applicable in any curriculum used in schools
Interactive practice ensures concepts truly sink in
Rich data helps teachers monitor progress and provide focused support
Teachers are empowered to make their classroom experiences much more fun, engaging, and social, with less lecturing and more project-based learning and peer tutoring

We learned a lot this past year, and I suspect we will learn much more this coming school year. The results so far have been promising. However, in our view, we’re just getting started. We got office space and started building a team only 10 months ago. We still have a long way to go to reach our vision for technology-enabled education.

Maintenance period complete

Fri, 05 Aug 2011 23:22:00 -0400

Summary: Yesterday’s maintenance period was completed and successful, but we ran into a problem that left us with a longer-than-expected period of read-only access (~5:00pm to 11:30pm PDT), as well as a few other side effects. We have already addressed these issues, but we would like to explain the situation for any users who were bothered by last night’s difficulties.

The following is slightly technical. If you are already bored or haven’t run into any problems using Khan Academy, feel free to ignore.

We had two primary goals for last night’s maintenance period:

Fix the occasional “Server Error” pages that users have been seeing randomly.
Fix some of the frustrating slowness users have been experiencing.

These two problems are related, and we needed to swap out a large piece of our technical infrastructure* to properly address the root cause. Hence the need for our read-only period.

Most of this transition went very smoothly. We put up an explanatory landing page that you may have seen, telling users, “We’ll be back soon.” Unfortunately, right when we were about to finish, we realized that we made a mistake with that “We’ll be back soon” page**. Due to this mistake, we were unable to get rid of that page and replace it with the fully functioning version of Khan Academy.

Once we realized this, we had to pull a number of time-consuming tricks*** to get the site back up and running. These tricks caused the extra delay, and it also left a few side effects that you may have noticed today:

When visiting www.khanacademy.org, users were redirected to khan-academy.appspot.com. This is perfectly safe, and it was only a temporary solution that we have now fixed.
Some users may continue to see the “We’ll be back soon” page long after we restored full functionality late last night. These users need to reload the www.khanacademy.org page, and then they should be all set.
If you experienced or continue to experience issues with the site that you think are connected to last night’s maintenance period, please comment on this post and we will work quickly to help you resolve your problem.

We apologize for all of the trouble, but there’s an upside.

The good news!: the original goal of the maintenance period was, at first glance, very successful. We will keep you up-to-date, but all evidence on our end suggests that www.khanacademy.org is now running much faster (woohoo!) and much more reliably (you shouldn’t see any more ugly “Server Error” pages) than before.

Thanks for your patience and understanding. We’ll continue to update you as we work to keep www.khanacademy.org chugging as quickly and smoothly as possible.

-Ben

* We were switching to Google’s new, highly improved High Replication datastore.
** We mistakenly set a far-future Expires header for the maintenance page. This caused a cascading series of caching issues between us and our users.
*** We used a combination of DNS changes and javascript redirects to work around the caching issues as effectively as possible.

Khan Academy undergoing maintenance 4:30pm - 10pm Thursday

Wed, 03 Aug 2011 19:28:00 -0400

We’ve been getting reports of server errors from some users. To fix this, we’ll be taking down the site at 4:30 pm PDT on Thursday 4th August (tomorrow!). We expect to be back online by 10pm (or earlier) the same day.

While the site is down, you will still be able to view all of our videos directly on YouTube. We’ll still have a simple version of our homepage up, but you won’t be able to do exercises, gain points or earn badges while the site is undergoing maintenance.

Once we’re back online, the site should be much more reliable. Apologies for the late notice, and thanks for your patience!