Localization is not translation

I have a degree in literary and specialized translation, so I'm biased toward thinking words matter. They do. But after years of marketing ZenMarket, a service that lets people abroad buy from Japanese stores, to customers in a dozen countries, and later building interfaces as a frontend engineer, I'm convinced translation is the easy part of localization.

What breaks is everything around the words

Here are the things I've seen go wrong most often, roughly in the order you'll find them.

Text length

Spanish and German run noticeably longer than English. Japanese is usually shorter but needs more vertical room to stay readable. Buttons and navigation that were designed around English labels overflow, wrap badly or truncate. Design with the longest language, not the first one.

Line breaking

Japanese has no spaces between words, so browsers break lines wherever they like, sometimes in the middle of a word or right before punctuation. Modern CSS helps: word-break: auto-phrase breaks at natural phrase boundaries in Chromium-based browsers, and it's a one-line improvement for any Japanese heading.

Names

In Japan the family name comes first, and forms usually ask for a phonetic reading (furigana) as well. A single "full name" field, or first and last name in Western order, produces wrong salutations in emails and messy data.

Addresses

Japanese addresses start with the postal code and prefecture and go from large to small. A form built around a US state dropdown makes Japanese users fight it, and the reverse is true for international buyers on a Japanese site.

Numbers, dates and money

Don't format them by hand. Intl.NumberFormat and Intl.DateTimeFormat exist for a reason, and yen has no decimal places, which is the kind of detail that breaks a price display nobody tested.

Payment

People pay differently in different countries. In Japan, convenience-store payment and bank transfer are still common. Elsewhere, a card or a local wallet is expected. Checkout is where a "translated" site loses the most money.

Marketing doesn't translate at all

Running multilingual marketing with a multicultural team across twelve markets taught me that the same product has a different reason to buy in each one. A campaign that works in one country can confuse or even offend in another, and a literal translation keeps every problem of the original while adding new ones.

What works is having native speakers write for their market from a shared brief instead of translating a master version. It costs more up front and far less than a campaign that doesn't land.

A short checklist

Before calling something localized, I check that the layout survives the longest language, Japanese lines break at sensible places, forms accept local names, addresses and phone formats, numbers and dates come from Intl, checkout offers the payment methods people actually use there, and copy was written by a native speaker, not just translated by one.

Translation gets the words right. Localization is making sure nobody notices the product wasn't built for them.