Acceptance of Credit Cards in Japan

1. Credit cards are accepted in almost every large shop and restaurants. But you will find that many smaller shops, Mc Donalds and some other fast food chains, sale locations ( e.g. large shop puts up a sale in the subway area ) - all these places do not accept credit cards.

2. Having to make a credit card myself - Visa and Master Card cards are most popular here. But as far as I could see - all cards are accepted. I wouldn't worry about that.

3. In grocery shops and convenience stores they just swipe, all other places uses either a PIN or your signature. They'll ask which you prefer, although very-very often only in Japanese but they'll try to make an effort and explain using hands :)

Japan is NOT a primarily a "cash-society", it's just that it costs a lot of money to make a contract with the credit-card company and every transition will cost ~3% for fees, so smaller businesses just don't want to do it.

Additional tip: keep a 10 000 yen bill with you ( around 100$ ), you will not easily find a place to spend it, because expensive places will have credit-card support and places where you'll need cash won't cost you that much.

1. Card acceptance in major cities is generally good. All department stores (like Yodobashi) will take credit cards and most small shops will take them as well, no issues here. I still suggest keeping cash on you as you could get surprised.
2. I had no issues using my MasterCard, I do not know about the others.
3. In my experience, the stripe is used much more.

Acceptance

Places expects foreigners paying a large amount are more likely to accept credit cards, such as:

1. Ticket office (but not vending machines) in major railway stations, e.g. JR West "Green Window".
2. Convenience stores, e.g. FamilyMart, LAWSON, 7-11.
3. Department stores.
4. Amusement parks, e.g. Universal Studio Japan (USJ in Osaka).
5. Taxis in major cities / urban areas.

However, you still need cash for having ramen, entering parks and temples, riding buses and for a lot of things. Make sure always have a good amount of cash with you. :)

Cards accepted

1. JCB (Japan Credit Bureau)
2. MasterCard
3. VISA
4. American Express

Other cards such as Diners Club and China UnionPay are accepted, but not as widely accepted as the aboves. For instance, ticket office of JR West and bag drop counters of Peach Aviatvion does not accept China UnionPay.

Using credit card in Japan

Usually stripe, some new terminals use EMVs. For some places like convenience stores, no signature is required for purchase under ¥10,000. Yet, I did not find any terminals accepts VISA payWave or MasterCard Contactless.

Good answers already, but just to add my 2 yen:

1. To withdraw money, the best ATMs are at Japan Post offices. Convenience stores ATMs do not always accept withdrawals, Japan Post ATMs always do, according to my experience. Japan Post offices are open less often, though.
2. Some places take a fee for credit card (see my picture below). It is quite rare though.

Wikivoyage has a list of banks and ATMs showing what cards they accept and how much they charge in fees (yes some are free).

I had no major problems with MasterCard for larger purchases in department stores, although lots of smaller places would not accept anything other than cash. Visa only works to get cash at 7-11, I've found no other place that accepts it.