Harken Chrome Extension

Never forget what you learn again.Harken is a smart flashcard app that uses spaced repetition to make remembering easy.Try it out  🙌Use Harken to remember anything for a lifetime.Harken is way more efficient than conventional study methods, and supports all kinds of learning. You can put almost anything on a card—images, audio, inline code, or code blocks.Learning JapaneseStudying for medical examsMemorizing vocabMastering JavaScriptRemembering famous works of artLearning personal financea10 cards leftSupermarketスパーHow does it work?Harken uses a science-backed learning strategy called spaced repetition to optimize your studying, so you can learn more in less time.With spaced repetition, you’ll review unfamiliar concepts more frequently than concepts you already know. This means you’ll learn exponentially faster with Harken than with traditional study methods.To remember one concept for 20 years, how long would you need to study?With traditional studying, you might review it once per week:Week1Week2Week3Week4Week5Week6Week7Week8Week9Week10Week11But with Harken, as you get more familiar with a concept, your reviews will get more spaced out:Week1Week2Week4Week7Week11Week6Week7Week8Week9Week10Week11Traditional flashcards:2+ hoursReview once a week for 20 yearsHarken cards:5 minutesReview on our spaced repetition schedule for 20 yearsUse the Harken extension to remember everything you readNow you can remember anything from any article on the web. The Harken Chrome extension allows you to quiz yourself on content from any article on the internet by using AI to generate questions with a single click. As you answer questions, easily add the ones you care about to your Harken for future review.Why Harken?Every feature is designed to support your long-term learning.FlexibleFormat however you like.Harken’s card editor includes support for rich text, images, inline code, and code blocks. No matter what you’re trying to remember, Harken is here to support you.Easy AccessYour cards go where you go.Harken is a responsive web app, meaning you can review and create cards on any device.ConvenientEasily import your Anki decks.We know your time is valuable. If you’re already using Anki, you can import all your decks and review history to Harken in just a few clicks. You’ll be up and running in no time.MotivatingTrack your progress.There’s no better feeling than a sense of progress. Harken’s stats page turns your reviews into useful charts to help you visualize just how much you’ve remembered.ResourcesOur StoryWhat Is Spaced RepetitionBlogPrivacy PolicyGet in TouchFollow Us on TwitterContact Us© 2026 Harken --- Go to AppOur mission is to help people remember the things they care about.We started Harken because everyone has trouble remembering what they learn.Most people who read books or take online classes either accept that they'll forget, or they spend even more time and money relearning what they forgot. That applies to us, too—as lifelong learners, we've experienced this firsthand, and it's super frustrating.With Harken, we're making this a problem of the past.Who We AreWe're both makers and lifelong learners, excited about helping people remember what they care about 💛If you have feedback for us about Harken, feel free to reach out on Twitter!Matt LimEngineer, blogger, mushroom enthusiastmattlim.meKatherine LiuDesigner, illustrator, dessert monsterkatherineliu.meResourcesOur StoryWhat Is Spaced RepetitionBlogPrivacy PolicyGet in TouchFollow Us on TwitterContact Us© 2026 Harken --- Sign InGet StartedEmail addressCreate AccountAlready have an account? Sign in hereOrResourcesOur StoryWhat Is Spaced RepetitionBlogPrivacy PolicyGet in TouchFollow Us on TwitterContact Us© 2026 Harken --- BlogUpdates from HarkenGo to AppA Primer on Spaced RepetitionWhat is spaced repetition?Simply put, spaced repetition is a studying technique that lets you memorize things more efficiently and effectively. For example, let's say you want to memorize the definition of “sangfroid” for the rest of your life. There are a few possible approaches you might come up with.Review the definition 20 or 30 times in a single day, until you're sure you remember it.Review the definition once a week for the rest of your life, to ensure you remember it even after a few years.Review the definition on a spaced repetition schedule, e.g. review it on day 1, then day 4, then day 11, then day 25, then day 60, etc. With spaced repetition, each time you successfully remember, the next review gets increasingly spaced out.There have been a bunch of studies about the efficacy of these approaches. The basic summary is as follows. With the first approach, you'll remember what “sangfroid” means in the short-term, but will most likely forget it after a few days or weeks. The second and third approaches are similarly effective, but the third is much more efficient. Over a span of 20 years, the second approach will take up ~2 hours of your life, while the third approach will take only ~5 minutes.Why does it work?There are two learning strategies that explain why spaced repetition works. The first is called active recall, and the second is called the spacing effect. Let's cover them one at a time.Active recall is basically a fancy word for testing your knowledge. Whenever you take a test, or try to remember what some word means, you're doing active recall. The idea is that actively recalling some idea, fact, or concept helps you remember it. This contrasts with “passive review,” which is much less effective. Examples of passive review include reading a textbook or watching a documentary, assuming you're not quizzing yourself while you read or watch. Have you ever read a really interesting non-fiction book only to forget it all a few months later? That's passive review at play—if you really want to remember what you read, it's much more effective to quiz yourself on the material than to continually re-read it. For a more in-depth explanation of active recall, check out our blog post about it.The spacing effect says that if you want to remember something, it's better to space out your reviews than to cram and do a bunch of reviews in a single day. For example, let's say you have ten reviews to spend. Instead of reviewing ten times the first day, you're better off using one the first day, then another a day later, etc. Further, there have been studies that show that a specific type of spacing is the most efficient. Specifically, instead of reviewing at fixed intervals (example 2 above), you should review at increasingly spaced out intervals (example 3 above)—the latter is just as effective as the former, but far more efficient.Forgetting curve without spaced repetitionForgetting curve with spaced repetitionThe Ebbinghaus forgetting curve (first chart) shows that people forget most of what they learn in just a few days. The steepness of the curve represents memory decay. But with spaced repetition (second chart), the rate of decay will slow after each time you review a concept—meaning that you'll remember the concept for longer. The time between each review increases and makes your studying more efficient.Now back to spaced repetition. Spaced repetition is really just a combination of active recall and the spacing effect! Put another way, it's just the practice of actively recalling something on a spaced schedule.What can you use it for?“Memorization” has a bad stigma for many people—maybe it's associated with cramming for the SATs or GREs, and dissociated from more important things like learning and understanding. However, it turns out that memory plays a key role in learning any subject. This may be unintuitive at first. It makes sense that spaced repetition might be helpful for learning a language or studying for exams. But what about learning computer science, or math, or chemistry? Even for these more conceptually deep subjects, spaced repetition is still useful—spaced repetition isn't just about rote memorization. It helps you memorize key details and concepts which form the foundation for in-depth understanding and mastery. Just as it's hard to speak a language if you don't remember many words, it's hard to understand a subject if you're constantly forgetting the fundamentals.Here are some uses of spaced repetition that we find particularly valuable:Learning a languageStudying for exams like the SAT and GRELearning a new computer science language or APIRemembering the most important concepts from non-fiction booksLearning about a complex topic like quantum physicsOther ResourcesIf you want to learn even more about spaced repetition, here are some resources we recommend:Spaced Repetition for Efficient LearningAugmenting Long-term Memory How can we develop transformative tools for thought? ResourcesOur StoryWhat Is Spaced RepetitionBlogPrivacy PolicyGet in TouchFollow Us on TwitterContact Us© 2026 Harken