How to turn on FSRS in Anki (desktop, AnkiDroid and AnkiMobile)

Open any deck's options, scroll to the FSRS section at the bottom and turn on the FSRS switch. It applies to your whole collection at once, not just that deck. Then leave desired retention at 90%, press Optimize, and keep Reschedule cards on change off. The steps below go through each of those.

Which version you need

If your app is older, update it first. Turn FSRS on in one place and let it sync; the setting is part of your collection.

Step by step

1. Back up first. On desktop: File > Create Backup. It takes seconds and gives you a way back.
2. Open Deck Options. On desktop, click the gear next to any deck and choose Options. On AnkiMobile and AnkiDroid, open the deck's options from the deck list.
3. Scroll to the FSRS section at the bottom of the page.
4. Turn on the FSRS switch. Anki can only enable FSRS globally, so every preset switches together.
5. Leave desired retention at 90% for now. That's Anki's default and a good balance of retention and workload. Anki desired retention explains when to change it.
6. Press Optimize. It fits FSRS's parameters to your own review history. Since Anki 24.06.3 it works with any number of reviews; with only a few hundred, the fit is rougher. If you use several presets, Optimize All Presets does them together.
7. Leave Reschedule cards on change off and save.

Why leave reschedule off

With it off, FSRS only affects cards as you review them, so your daily workload stays where it was and shifts gradually. With it on, Anki recalculates every due date immediately, which often makes a large number of cards due at once. Anki's manual says it isn't recommended when you first switch from SM-2. It also adds a review entry to every card, which grows your collection.

Check your learning steps

FSRS works best when learning and relearning steps finish within the same day. Anki's manual suggests steps like 10m or 30m, recommends against steps of 1 day or longer, and suggests keeping the number of steps small. If your preset has a step like 1d, shorten it. Anki learning steps and Anki relearning steps cover both.

If you used the old FSRS script

Before FSRS was built in, some people ran it through Anki's custom scheduling box. If you did, clear that box before turning on the built-in FSRS.

After turning it on

• Re-optimize about once a month. Anki's FAQ says that's more than enough.
• Press Again when you forget. FSRS treats Hard as a pass. See Hard vs Again.
• Some SM-2 options disappear. Settings such as Graduating interval and Easy bonus are hidden while FSRS is on, because FSRS doesn't use them.

To go back to SM-2, turn the same FSRS switch off.

Next steps

• What is FSRS in Anki, and should you turn it on?
• Anki FSRS settings explained

In Decks

Decks uses SM-2, so there's nothing to turn on. How spaced repetition works in Decks explains its scheduling.

Sources

• Anki manual: Deck Options, FSRS
• Anki FAQ: Frequently asked questions about FSRS