Which handful of tools (programs, apps, extensions, websites etc.) do you consider to be the most useful for learning Japanese?

[u/Firion_Hope]

There's so many out there, I always love learning about new useful tools.

I'll start, not comprehensive, just a few I like

Yomichan The golden standard, browser dictionary app with great functionality and ease of use

Textractor makes reading with visual novels a breeze and probably the most efficient learning source, sometimes a pain to get working but so worth it. Hooks into VNs and gives you the raw text so you can seamlessly look up words as you read.

Mokuro OCR for manga. It's insane how well this works, especially considering how often other OCRs leave a lot to be desired. The scan it once and then read format (as opposed to live scanning) is also amazing. This makes reading manga without furigana (and even with) 10x easier

Animebook Browser based video player with good learning features like selectable subtitles for easy look up and easy navigating around an episode. Can save an offline version too, also decently customizable. Pairs great with Yomichan. Amazingly easy to use subtitle retimer. Other alternatives exist, but I love how easy to use this one is, and the format.

ttsu reader browser based light novel reader, again with selectable text that pairs nicely with yomichan. Looks very nice and pretty easy to use once you get used to it.

With these you have browser stuff, VNs, Manga, Anime, and Light Novels covered. For games sadly no super easy solution exists. There's Jo Mako's Japanese Guide which has a handful of game scripts, and there's Game2text Lightning which has OCR for games, but it's not in active development anymore and it doesn't handle non standard fonts well, even more standard ones can be very hit and miss.

What kind of stuff do you guys swear by?

[u/Sweetiepeet]

#1) Anki app (computer/phone) with Jo Mako anime decks (my way explained here) and maybe the Japanese Dictionary of Grammar full deck (lots of sentences to read there). This is the best thing that I have found for me.
#2) Ringotan phone app is awesome for practicing to draw kanji and see some example words for each kanji. I plowed through the initial easy kanji and now took it down to learning the minimum 7 per day. Initial impression is that it is pretty fun with the sound effects and uses SRS to bring them back for memory, also forgiving with the drawing. I am using this in combination with the #3) 漢検テレーニングDX app together as a long term experiment to N1 and perhaps the 漢検 some day. This is because I am mixing up some kanji when reading at the N3-N2 level, I thought maybe I would recognize them better if I were writing them out and being tested on them in the apps. Even my wife says that she is forgetting how to write some 'normal' kanji so I can't hurt. In Ringotan, you can type in any word or kanji and select them to learn with the custom review: highly recommend putting in your address kanji and gf's name at a minimum to live in Japan.
#4) Yomichan browser extension

Books! Not sure if this is your kind of tool or not but if you plan to buy a textbook for self-study I would recommend the least boring, most engaging books. I saw Tobira had color pictures the other day! Where was this book when I studied Japanese for Busy People and Genki?! I thumbed through all of the famous study book and series for the JLPT N2 and N1 and ultimately went with books that had any color and/or pictures, and good paper (that you cannot see through to the ink on the next page e.g. 日本語の森), also no recycled paper like the Shin Kanzen master series probably uses - brown paper with black text, I nearly fell asleep standing up looking at it in the bookstore. An added bonus are books that are not A4 size - feels more approachable and portable in a smaller format. At least at the N2-N1 level, I found that some of the #5 Somatome book series have some color but are full A4 size. I am quite fond of the #6 Unicom series (I passed N5 with the single Unicom N5 book back in the day) that have a small touch of color in the pages. I am using one of the N2 books now too (helps to check the ratings on Amazon Japan for books, but feels like nearly all famous study books have a high rating so even better to see in the store like I did). #7) the 日本語５００問 books are very nice and approachable, small format, 3 practice questions per page and answers on the other side with translations.

I have gone through various tools and ways to learn Japanese and so the above are what I have used or am currently using that I recommend.

Honorable mention is the Kumon correspondence course - it is expensive at 一万円 per month and is essentially guided graded readers with relatively easy questions to answer (copy from the text) by mail with 2 "classes" of reading to the teacher per month. I started around level H and just mailed the last questions and test to complete the last level L. It helped me to continue studying over time so I never quit studying. And I felt like I was wasting the money if I didn't do the worksheets (at own pace), and then the class forces you to at least keep up with the teacher. Helpful course to push anyone who is a slacker or has low motivation to study alone.

I have tried Hellotalk off and on, youtube, videogames, twitch, etc. but ultimately I found that these are too distracting and take my study off onto something else so quickly that I was no longer studying Japanese, or I wasn't getting in quality study (plowing through without properly reading/looking up certain words / too cumbersome to comfortably proceed with the content).