Lesstep
Checklist · 20 items · Updated October 30, 2026

Japanese localization checklist

Translating your strings is the easy part. These are the twenty things that still go wrong when people in Japan use a web app, each with a test you can run yourself and a page on how to fix it. Skip the ones your app doesn't have: if it takes no payments, the yen item doesn't apply.

Free check: send your app's URL, and the repository if your code is public, to support@lesstep.com. Within two business days, we'll tell you which of the twenty your app runs into, for free. No payment details needed.

Typing and forms

  1. Enter sends the message while typing Japanese. Try: with the Japanese input built into macOS or Windows, type a word in your chat box or form and press Enter to pick the kanji, in Chrome and in Safari. Nothing should be sent. In Complete: fixed in the pull request.
  2. Forms that reject numbers typed in Japanese. Try: with Japanese input on, type a postal code and a phone number. The digits arrive full-width (１２３) and the hyphen key types ー; the form should take them. In Complete: fixed in the pull request.
  3. Full-width spaces that get past your checks. Try: save a name that is only a full-width space (U+3000), and search for two words with one between them. The name should be refused, and the search should look for two words. In Complete: fixed in the pull request.
  4. Address forms in the Japanese order. Try: fill in your address form as someone in Japan. It should start with the postal code, list the 47 prefectures in their standard order, and go from the prefecture down to the building. In Complete: fixed in the pull request; filling in the address from the postal code if you want it.
  5. Japanese phone numbers in forms. Try: enter a 10-digit number such as 03-XXXX-XXXX and an 11-digit mobile number, including one that starts with 060. Both should pass, and +81 should drop the first 0. In Complete: fixed in the pull request.

Text on the screen

  1. Kanji in their Chinese shapes. Try: on a Japanese page, check that <html> has lang="ja" and that font-family has no Chinese font such as PingFang SC or Microsoft YaHei. In Complete: fixed in the pull request.
  2. Japanese headings that break in the middle of a word. Try: read your Japanese headings at phone width. No line should break inside a word or start with a small kana. In Complete: fixed in the pull request.
  3. Length limits that break in Japanese. Try: look at link previews, character limits and word counts with Japanese text. A preview of only “...”, a limit that holds a third as much, or a whole sentence counted as one word are the signs. In Complete: we find them and tell you how to fix them.
  4. Japanese vertical text that comes out sideways or upside down. Try: if you set text vertically, read a Japanese title, a line with English in it and a date like 10月22日, then page to the end. Nothing should be upside down, and the last page should open. In Complete: fixed in the pull request.

Dates and money

  1. Dates that come out wrong for Japanese users. Try: set your computer to Japan's time zone, pick a date and save it. It shouldn't come back one day early, and it should read year first, as in 2026/10/30. In Complete: fixed in the pull request.
  2. Japanese era dates that come out wrong. Try: if you show or accept dates in the era, try April 30 and May 1, 2019, when the era changed, and year 1, written 元年. In Complete: fixed in the pull request.
  3. Japanese public holidays your app gets wrong. Try: if you count business days, check that May 6 and September 22, 2026 are days off. In Complete: fixed in the pull request.
  4. Stripe charges 100 times too much in yen. Try: if you take yen, charge ¥1,980 in Stripe's test mode. A charge of ¥198,000 means the price was multiplied by 100. In Complete: fixed in the pull request.

Search, lists and URLs

  1. Search that finds nothing in Japanese. Try: search for a two-character Japanese word, such as 検索, that appears in the middle of a sentence in your data. It should be found. In Complete: we find it and tell you; the fix means rebuilding the search index, so we agree with you whether it goes in the pull request.
  2. Japanese lists sorted in the wrong order. Try: sort a list of Japanese names. They should come in the order of how each is read, not with katakana after hiragana. In Complete: we find it and tell you; if names have no reading in kana, we agree with you whether to add one.
  3. Japanese titles that give an empty URL slug. Try: give a post or heading a Japanese-only title, such as 日本語タイトル. It should get a URL and an anchor of its own, not an empty one. In Complete: fixed in the pull request.

Email, files and PDFs

  1. Japanese email subjects that arrive garbled. Try: have your app send you an email with a Japanese subject and sender name. Neither should arrive garbled. In Complete: fixed in the pull request.
  2. Japanese CSV files that open garbled in Excel. Try: export a CSV with Japanese in it and open it in Excel on Japanese Windows; then import a file that Excel saved. Both should read correctly. In Complete: fixed in the pull request.
  3. Japanese file names garbled on upload and download. Try: upload a file named 請求書.pdf (“invoice”) and download it again. The name should come back the same. In Complete: fixed in the pull request.
  4. Japanese text missing from your PDFs. Try: make a PDF with Japanese in it, in regular and bold. It shouldn't show empty boxes, other letters or blank space, or start a line with 。. In Complete: fixed in the pull request.

A free check of your app

Send your app's URL, and the repository if your code is public, to support@lesstep.com. We look at your public pages and code, and within two business days reply with the items your app runs into and where. It's free, and we don't need a login or payment details. Here is what a check finds, with fixes we sent to open-source apps.

Lesstep translates web apps into Japanese and delivers them as one pull request. Complete (US$249) runs your app, checks every screen in Japanese, and fixes what it finds in the same pull request. The first step is a free sample.

macOS and Safari are trademarks of Apple Inc.; Windows and Excel are trademarks of the Microsoft group of companies; Chrome is a trademark of Google LLC; Stripe is a trademark of Stripe, Inc. This page is not affiliated with or endorsed by any of them.

More: Enter sends the message while typing Japanese · Stripe charges 100 times too much in yen · Kanji in their Chinese shapes · Japanese headings that break in the middle of a word · Forms that reject numbers typed in Japanese · Dates that come out wrong for Japanese users · Address forms in the Japanese order · Japanese phone numbers in forms · Japanese text missing from your PDFs · Search that finds nothing in Japanese · Length limits that break in Japanese · Japanese lists sorted in the wrong order · Japanese email subjects that arrive garbled · Japanese CSV files that open garbled in Excel · Japanese titles that give an empty URL slug · Japanese file names garbled on upload and download · Japanese era dates that come out wrong · Full-width spaces that get past your checks · Japanese public holidays your app gets wrong · Japanese vertical text that comes out sideways or upside down · Japanese localization for your web app