A free katakana practice test: a character appears, you type its romaji or pick it from four, and you know at once if you got it right. Twenty questions a round, from the 46 basic characters to the combinations, no account needed.
Twenty characters a round, in random order. The quiz starts as soon as you pick.
Not sure of one yet? Open the katakana chart and watch it written.
Little and often, from memory, mixed up. Ten minutes a day of recalling characters, the way this quiz makes you, beats an hour of looking at the chart, and the characters you miss should come back sooner than the ones you know.
See a character again just before you would forget it: the next day, then three days later, then a week. Each recall at the edge of forgetting lasts longer than ten in a row. That is spaced repetition, and it is how Naraio schedules reviews.
Learn row by row, but test mixed: in order, you guess from the position. Katakana's look-alikes are the hard part (シ and ツ, ソ and ン, ク and ワ), so meet them side by side.
The direction of one stroke is all that separates シ from ツ, and you only notice it by writing. A few tries on the chart's board do more than fifty glances.
Once single characters come fast, read words: コーヒー, テレビ, パン. Menus and packaging are full of katakana, and each word is one you half know already.
Every character with its stroke order and a board to draw it.
The same quiz for the first script: particles, verb endings, furigana.
Naraio's path starts with hiragana and katakana and goes all the way to N1, with reviews that bring back whatever you miss. It opens soon, free to start: leave your email and you're among the first in.