How to Choose a Spaced Repetition App That You’ll Use
I evaluated Anki, Mochi, RemNote, Quizlet, and others to find out which tools are built for lifelong learners.
I was sitting cross-legged on my living room floor, halfway through Daisy Christodoulou’s Seven Myths About Education, when I read a paragraph I could hardly believe.
She was arguing that memorization — what I used to think was the lowest and most useless form of learning — is the foundation of critical thinking. You can’t think critically about something you don’t know. You can’t evaluate an argument if the relevant facts aren’t already in your long-term memory, ready to be compared, weighed, and challenged in real time.
I closed the book. Stared at the ceiling.
The next day I Googled “what’s the best way to move things from short-term to long-term memory?”
The evidence pointed to spaced repetition, which is the finding that reviewing material at increasing intervals improves long-term retention. I downloaded a flashcard app called Anki; I’d heard about it from my ex-partner, a medical student at the time.
Within weeks, I noticed it works. You can choose what you remember and store in your long-term memory.
I used to think I just wasn’t as sharp as friends who could recall specific historical dates or quotes mid-conversation. Turns out it was a choice and a practice that even gets easier with time. The more you already know, the easier it is to remember new information, because you can attach it to what’s already wired in your brain.
Facts I’d read months ago started surfacing at the right moments, for example, in conversations, while writing.
I felt like I’d found a superpower, a cheat code nobody had told me about. I hadn’t learned about it in teacher training. It wasn’t common knowledge at the school where I taught. It could have saved me hundreds of hours across my undergrad and graduate degrees.
I wanted to grab every student and knowledge worker I knew by the shoulders and shake them.
That was three years ago. Since then, I’ve hit many of the obstacles that get in the way of building a new habit and learned how to write better flashcards. I wrote a six-part series about how to remember anything you want using spaced repetition. This article is about the software for managing your reviews.
If you’ve never heard of spaced repetition, start with an explainer on the evidence behind spaced repetition Part 1 of the How to Remember What You Read series. This article assumes you already know the basics and it covers:
The three criteria that matter when evaluating any spaced repetition tool
A comparison matrix of Anki, Mochi, RemNote, NeuraCache, Brainscape, Quizlet, and Space, evaluated across algorithm, card creation, data portability, and platform availability
A look at the AI-powered spaced repetition newcomers and why I wouldn’t recommend them as standalone systems
My personal setup and recommendation
Let’s begin.
The Three Criteria That Actually Matter
When you start comparing spaced repetition tools, you’ll find dozens of features to evaluate, such as integrations, themes, gamification streaks, AI assistants. Most of it is noise.
I’d argue only three things determine whether a spaced repetition software will help you remember what you learn: the algorithm scheduling your reviews, the quality of the cards you’re reviewing, and whether you’ll use the tool consistently enough for any of it to matter.
1. What’s the underlying spaced repetition algorithm?
A spaced repetition algorithm determines when you see each card again. Too soon, and you waste time reviewing things you already know. Too late, and you’ve forgotten, so the card resets to square one. The algorithm’s job is to find the latest possible moment you can still recall the answer, so every review session is maximally efficient.
The algorithm you want to look for is called FSRS — the Free Spaced Repetition Scheduler.1
Why this matters for your choice: When a tool says “spaced repetition” on its website, that can mean anything from a rigorous, research-backed adaptive scheduler to a simple “show it again in 3 days” timer. While it might sound trivial it’s like the difference between Google Maps that recalculates your optimal route based on traffic and a compass that points you in roughly the direction you want to go to.
What to look for: Does the software name and document its algorithm? Can you find published research or open-source code behind it? If the answer is “proprietary — we learn your memory patterns” with no further detail, treat that as a flag. Not necessarily because the tool is bad, but because you can’t verify the claim.
2. What’s the quality of card creation?
A spaced repetition system is only as good as your flashcards. Bad cards — too long, too vague, too easy to fool yourself on — are the reason most people quit. This is also why most AI-powered flashcard generators are disappointing as standalone systems, but I'll get to that later.
Why this matters for your choice: Several new AI-first tools promise to generate flashcards automatically from your lectures, PDFs, or notes. The AI card generators I've tested produce cards that are too broad, too verbose, and too easy to fool yourself on. They optimize for quantity, not quality of retrieval. The best tools either give you full control over card creation or offer AI assistance that you can edit and refine — not AI that replaces your judgment entirely.
What to look for: Can you create cards manually with full formatting control? If there's AI generation, can you edit every card before it enters your deck? Does the tool encourage atomic, single-fact cards, or does it default to paragraph-length answers?
Here's what that looks like in practice:
Look at the screenshot of this card from an AI tool landing page. An AI tool auto-generated it from a cell biology lecture. The front asks: “What is the main function of mitochondria?” The back answers with a multi-sentence explanation covering ATP production, oxidative phosphorylation, and cellular respiration.
This card violates the principles of effective knowledge formulation because it packs too much complex information into a single answer. The back of the card contains three distinct pieces of information, making it a complex item rather than a simple one:
The end product (ATP).
The specific biological mechanism (oxidative phosphorylation).
The definition of that mechanism (converting nutrients into usable energy).
By grouping these together, you risk falling into an evaluation trap where you cannot objectively grade your recall. If you review the card and successfully remember “ATP production” but forget “oxidative phosphorylation,” you have to decide whether to mark the card as forgotten or remembered . If you click “remembered,” you will under-review the part you forgot, and if you click “forgotten,” you will over-review the part you already know
Instead, you should break complex items down into the smallest possible conceptual units so that the brain can process them in a simple, continuous path.
To fix this, you must atomize the facts and use context cues to ensure precision. Here is how you could break it down into three high-leverage cards:
✅ Card 1 (The Outcome):
Front: [Cell Biology] The primary function of mitochondria is to produce usable energy in the form of {{c1::ATP}}.
Back: ATP
✅ Card 2 (The Mechanism):
Front: [Cell Biology] By what specific process do mitochondria produce ATP?
Back: Oxidative phosphorylation.
✅ Card 3 (The Definition):
Front: [Cell Biology] During oxidative phosphorylation, mitochondria produce ATP by converting {{c1::nutrients}}.
Back: nutrients
For a deeper dive into formulating effective flashcards, see Part 2 of the How to Remember series, on card creation principles.
3. Will you actually use it?
Access to the best gym won’t build muscle unless you show up and train. Spaced repetition works the same way. You can have a great algorithm and learn how to write great flashcards, but you need to use them consistently to see results.
So the third filter is personal: what makes you likely to stick with this?
For some people, that’s an iOS app because they do their reviews standing in line at the supermarket, and if there’s no iPhone client, they won’t do them at all. For others, it’s a beautiful, modern interface because opening an app that looks like it was designed in 2003 creates just enough friction to skip the session.
Other friction factors: How fast can you create a card? Can you review offline? Does the tool integrate with your existing note-taking system? Is there a desktop app for creating cards and a mobile app for reviewing them?
What to look for: Check in with yourself on what makes you want to use a specific tool. If you’ve tried Anki before and bounced off the interface, that’s a sign you shouldn’t ignore.
This post continues for paid subscribers with the full comparison matrix, tool-by-tool analysis, and my personal recommendation.