Catching Up On Your Anki Reviews

So it happened: you’ve been studying with spaced repetition, but then you missed a day, or a few days, or a month. Life happens. If you claim you’ve never done this, I guarantee you haven’t been using an SRS for long! Unfortunately, when you come back after one of these breaks, you’ll likely have a lot of due cards, because you don’t stop forgetting and your cards don’t stop becoming due.

Fear not, you can catch up and get back to normal. This post may be long, but that’s because it covers a wide variety of situations you might find yourself in. If you’re currently suffering from a pile of overdue cards and you’re impatient, jump to the section under Strategies that matches the amount of time you’ve missed.

Background

What not to do

First, in the immortal words of Douglas Adams, don’t panic. No matter how far behind you are, you absolutely can get caught up again. It probably won’t even be as hard as you think, and you can use some planning and psychology to make it easier.

Second, don’t “reset” your deck and remove the scheduling history for all the cards that are behind. Back when I was paid to answer support questions, “How do I reset my deck?” was one of the most popular questions on the Anki forums. Although such a “reset” may be tempting since it gets rid of all the overdue cards, this is absolutely never a smart move, because no matter how far behind you are, there will be some cards that you remember well, and you lose their progress forever when you reset the deck. For weeks or months afterwards, you’ll be wasting your time clicking “Easy” on “new” cards you already know! Resetting history is the spaced-repetition equivalent of burning your house down and rebuilding it because it needs a few thousand dollars in repairs. Sure, you don’t have to do the repairs anymore, but that’s missing the point.

It should go without saying that I’m not going to tell you how to reset a deck. If you’re determined to burn down the house, you can figure it out yourself! (And remind me never to insure you.)

The daily limit

I need to mention one more thing about large backlogs: if you’re using Anki and you haven’t messed with the settings much, you might not notice a scary number immediately – it might just say you have 200 reviews due and leave it at that. By default, Anki decks have a daily limit of 200 reviews per day to avoid scaring people in exactly this situation – if there are more, the full number doesn’t show up.

But you’re already reading this page and know not to be freaked out into giving up on Anki forever. To figure out how to best handle your backlog, you’re going to want to know what you’re dealing with. So if you have a daily limit set on your deck, lift it: open your deck options, choose the Reviews tab, and raise Maximum reviews/day to 9999. In some of the strategies presented in a moment, you might want to drop it down again, but for best results, you want to start out with a complete and sober assessment of the situation.

Why no automated backlog management tools?

Some spaced-repetition programs have tools to “pause” reviewing so that all cards get shifted forwards 7 days when you take a 7-day vacation, or dynamically readjust all cards in your collection to make all of them appear just a little bit later and get rid of the backlog. Anki doesn’t. That might seem lazy, or sadistic, or designed to demotivate people, depending on how charitable you’re feeling, but I agree with Anki’s design philosophy and consider these tools harmful.

Here’s the problem: the existence of the tools invariably leads people to underestimate the effects of missing a bunch of study. Clicking Mercy or Holiday or Reschedule, or whatever your system calls it, takes only seconds and makes the backlog magically disappear with a puff of smoke, but it only makes the backlog disappear on paper. The backlog is still there in your brain, which means that the spaced-repetition algorithm will perform noticeably worse in the near future as it pretends that your cards were due at a different time than they actually are. Depending on the exact method of rescheduling, a reschedule can cause weeks or months of knock-on effects and decreased learning efficiency.

As people use these tools, often more frequently than they would need to because it seems so easy, the effectiveness of their spaced-repetition study invisibly erodes without giving them any indication of why or just how much they’re getting set back every time they click the button. Sooner or later, they give up on spaced repetition altogether, and who can blame them? It’s not working well!

The real problem, of course, is not the spaced-repetition scheduler, but the fact that you skipped reviewing for two weeks. By letting you reschedule automatically, the scheduler wrongly takes on the blame for your study practices. Even if dealing with a pile of 1,000 cards isn’t much fun, it keeps the pain where it belongs – where it highlights what you did wrong and how you can do better in the future. That’s what pain is for. It’d sure be nice if we could avoid the pain altogether, but unfortunately human memory doesn’t work that way (if it did, we would have no need for spaced repetition in the first place!).

A relatively innocuous type of rescheduler simply spreads all the overdue reviews out over a period of time, leaving all non-overdue reviews alone. The pain isn’t as obvious, but you’re still going to notice a lump of a bunch of extra cards, which might be enough to keep the feeling of responsibility with you where it belongs. I don’t like this approach either, though, because it denies you any future flexibility in how you catch up. If you decide you can do 150 extra cards per day and spread it out over 5 days, reschedule the cards, then the next day discover you’re going to be working 14-hour days for the remainder of the week, you’ll immediately get behind again (and even more cards will end up overdue). The strategies presented here require a bit more manual effort, but they leave you in control of your relearning at all times and keep you both motivated and aware of the situation.

Strategies

I am unaware of any single strategy best suited to tackle every pileup of overdue cards. The best approach depends partly on your personal preferences, but most importantly it depends on how long you’ve gone without reviewing, so I’ll break down the following suggested strategies by that factor.

One day

If you just missed a day (this only barely qualifies as a “backlog”), the most appropriate strategy is the Nike strategy: Just do it. Your “due” number looks a little higher than it should, but so what? Put on some good music that doesn’t distract you too much, grab yourself a hot beverage, and sit down and do the reviews. You’ll be through it soon enough. No big deal.

Indeed, taking a day off intentionally every now and then isn’t the end of the world. Sometimes life gets complicated and you don’t get to your reviews one day, even with your fancy mobile app that lets you study while you’re waiting in line. Just be sure you keep the missed days to a minimum; I like to target no more than 2 per month. Also, remember that if you miss a day it’s absolutely critical that you catch up the following day; if you miss two days in a row, then you have a real backlog that weighs on your mind and makes you even less likely to start catching up. (Funny how human psychology works, isn’t it?)

A few days

If you get up to a couple of days and you use Anki more than lightly, you probably won’t be able to get through the entire backlog in one sitting, or even one day. (I once did over 2,000 reviews in one day because I was way behind and just wanted to get it over with, but it took me over 8 hours!) I think this timeframe is the most suited for improvisation in catch-up methods, so pick from the three below or make up your own.

Use the daily limit

The simplest option is to set the daily review limit (see The daily limit) to a number of cards you can stomach, and do all the cards that Anki doesn’t hide from you every day until you’re caught up. If you’re just a couple of days behind, this will work fine, and it’s easy and allows you to pretend nothing is wrong.

Suspend overdue cards

A more complicated but potentially more attractive option is to suspend all of the overdue cards, pretending they don’t exist. You’ll be left with only the cards that were originally due today. If you leave the overdue cards suspended and go back to daily review, all other cards will continue to become due normally and be reviewed at the intended time; there will just be some cards left out.

Of course, you don’t want to leave that random set of cards out forever. Every day, you unsuspend and review as many of the overdue cards as you can handle. If you can’t do any additional cards on some days, that’s fine – just finish all the due cards, as you would on any other day. Eventually, you’ll have them all back in circulation again.

Of course, the sooner you get through all the overdue cards, the better; the longer they stay out of circulation, the more likely you are to forget them. (If this weren’t true, they wouldn’t have been due in the first place!) But with this strategy, no matter how long it takes you to catch up, the damage is contained to the small set of cards that went overdue.

I find this approach very attractive psychologically. It matches the “stop the bleeding” philosophy used in systems that are susceptible to cascading failures. For example, if an airline is suffering flight delays or cancellations, they will usually avoid rerouting or delaying any passengers who haven’t already been affected. Those who were affected have to wait until there’s room to work them in on a new flight without bumping anyone else, and everyone else moves along as if nothing was wrong. This looks unfair to the people who happened to get delayed, but it contains the failure – which is critical, because the effects of further failures are highly unpredictable and can rapidly become much worse than the original problem. (Power grid failures are among the most spectacular examples: the failure of a single piece of equipment can take out power for millions of customers if uncontained.)

In a spaced-repetition context, the cascading failure occurs when you fall further behind or give up on spaced repetition entirely because the prospect of catching up is so challenging. The power of this effect is not to be underestimated; I’ve experienced it myself multiple times, and here I am still with it after ten years, so I’m not exactly a spaced-repetition slacker.

Anki recipe: To suspend all overdue cards, search for prop:due<0 in the browser, give all those cards a tag with Ctrl+Shift+A, such as Overdue20200831, and suspend them from the right-click menu or by pressing Ctrl+J. When you’re ready to unsuspend some cards, search for is:suspended tag:Overdue20200831 and pick some cards to unsuspend; they’ll show up as due for review immediately.

Sort by relative overdueness

If you’re willing to risk a little less psychological safety, it’s possible to do better than either of the above methods. Anki normally shows due cards in random order, so you might end up reviewing cards that you have little chance of forgetting (say, ones with an interval of years) before cards that you urgently need to see immediately (say, ones with a three-day interval that are due today). This ordering means you’ll likely end up forgetting some cards you wouldn’t have had to forget.

You can’t adjust the order Anki shows cards in within a normal deck, but you have many options if you use a filtered deck. The option you want here is “relative overdueness,” which orders cards due for review by the ratio between the number of days they’re overdue and their total interval. So a card that has an interval of 5 years and is overdue by 10 days will come well after a card that has an interval of 3 days and is overdue by 1 day, because the first card is only about 0.5% late, while the second card is 33% late.

This method is particularly useful as a stopgap measure if you know you aren’t going to have enough time to make much progress on your backlog today but you do have a chance to do at least some reviews: you can arrest the forgetting of the most vulnerable cards, making it less harmful to leave the remaining ones.

The downside of this approach is that unless you get creative and add some more complexity, you can still see how many cards you have left to review, and you don’t get a chance to get “caught up” again until you clear your entire backlog. Suspending the cards doesn’t work because suspended cards won’t ever be selected when building a filtered deck. You can permanently move all of the overdue cards into separate decks and set the daily review limit on those decks to 0, then pull only cards in those decks for filtered-deck study, but then you have to deal with sorting the cards back into the correct permanent deck locations later, so this can be a real pain in the rear.

Anki recipe: Choose Tools > Create Filtered Deck, remove any deck portion from the search (unless you want to catch up on just one deck), select Relative overdueness from the drop-down, and ensure that Reschedule cards… is on. You’ll want to rebuild the filtered deck each day using the Rebuild button that appears on the overview screen after clicking into the deck; this will re-sort all due and overdue cards to match their relative overdueness today. As you review cards, they’ll be automatically returned to their original deck. If you want to stop using this method before you’re caught up, you can delete the filtered deck to immediately return all of its cards to their original location. Read more on filtered decks.

A couple of weeks

If you use Anki seriously, now you have more than a thousand reviews. (If you have fewer than five hundred, go back to the previous section – the strategies there will work fine for you.)

Since it’s likely going to take you a few days to catch up, your first step is to prioritize – are there certain decks or tags whose content you’re more likely to forget, or which you need to know in the short term? If so, those are your first priority. You also may want to think about balancing the difficulty of your material; if some material is way harder than other material, it’s probably best to mix it in rather than leaving it to the end, or continued catch-up reviews might become infuriatingly difficult.

If you have some material in your collection you don’t care about anymore, now is a great time to delete it – there’s no point in spending effort to relearn forgotten material that you don’t want to remember anyway!

Now that you’ve gotten your priorities straight and your collection cleaned up, your overriding concern is making sure you maintain psychological safety. To keep yourself motivated, you need to split your backlog into manageable chunks and see continuous progress. You also need to continue reviewing anything you’ve caught up on, so that you don’t lose ground again. If you keep moving forward, sooner or later you’re guaranteed to catch up – you have a finite number of overdue cards, after all – but if you start sliding backwards again it will become demoralizing.

Here’s the trick that has worked for me several times: take all of your content out and gradually reintroduce it as the additional workload becomes manageable. This strategy is much like the “stop the bleeding” strategy suggested previously, but it works deck by deck to produce a greater sense of progress.

Start by moving all of your decks under a new superdeck called “Unused” or “Inactive” or something to that effect. If you only use one deck, create a second “Unused” deck and move all your cards into that. Change the options on the unused deck to have 0 reviews and 0 new cards per day. Voilà, you now have 0 cards due! No backlog anymore. From now on, your other decks constitute your “collection”, which you’ll review every day as usual, while the Unused deck is a repository of useful material you can pick up again when you choose.

When you’re ready to start on that material, pick a deck to pull the material from (I like starting with the smallest one so I see immediate progress), create a new deck with the same name in your main collection area, and move some cards between the old and new deck, which will make them appear due again. Review and relearn those cards, then repeat as needed. Once you’ve removed all the cards from an unused deck, delete it so you can see the list get smaller. Keep doing this, and soon enough the Unused deck will be empty.

Long enough to make most of your collection due

You left spaced repetition alone for months or years, and now you’re coming back. You might find that now a majority of your collection is due, and that could be thousands of cards. Hopeless?

Well, we’re beyond panic at this point, it’s more like resignation. But it’s not time to give up, because there’s still a lot of useful information in that collection! Further, you have significant reason for hope: since so many of your cards are already due, it’s already almost as bad as it’s ever going to get. Unlike when you’re only a day or two behind, a rather low number of additional cards – maybe low enough to count on one hand, depending on exactly how far behind you are – become due each day. This means you can work through the backlog much faster than you might expect – your daily due reviews will contain almost exclusively the cards you’ve forgotten and are relearning, and the overdue pile isn’t growing.

For the most part, the strategy in the previous section will still apply to you. However, prioritization is even more useful now. Since you’ve been away for months, take this opportunity to look over your collection with a discerning eye and remove any material that’s outdated or no longer useful to you. A couple of hours now could save you a lot of pain and relearning time. Also, consider removing leeches or near-leeches and material with low eases (say, below 160%) – these will be the hardest cards to relearn, so if you can determine many of them are not worth it, your journey will get much easier.

Anki recipe: To find cards with an ease of less than 160%, search for prop:ease<1.6.

Another useful trick is to pull all the cards that aren’t yet due from the delayed decks first. This will have no immediate effect at all on your backlog numbers, and it won’t make that much difference since there aren’t a lot of new cards becoming due anyway, but there’s a certain pleasure in knowing you won’t get even one card further behind.

Good luck!