A localization testing checklist for online stores

Before you launch in a new language, check five things in the live store, not just in your translation files: text that never got translated, currency and number formats, dates, address forms, and layouts that break when words get longer. Then run your most important flow, usually checkout, from start to finish in that locale.

Localization testing is checking that your product works and reads correctly for a specific market: language, currency, formats and local conventions. Translation tools are good at the strings. The bugs that cost you customers tend to sit around the strings.

Key takeaways

• 76% of online shoppers prefer buying with product information in their own language, and 40% say they never buy from sites in other languages (CSA Research, 2020).
• Most localization bugs come from formatting and layout, not from bad translations.
• Test the running store per locale, end to end, not just screenshots of single pages.

Why it's worth getting right

CSA Research surveyed 8,709 consumers in 29 countries and found that 76% of online shoppers prefer to buy products with information in their native language, and 40% will never buy from websites in other languages (CSA Research, Can't Read, Won't Buy, 2020).

So a checkout that switches back to English at the payment step isn't a cosmetic issue. For a big share of shoppers, it's the moment they decide your store isn't for them.

1. Text that never got translated

Go through the whole flow, not just the homepage. The usual suspects:

• Buttons and labels added after the last translation round.
• Error messages and empty states, which almost nobody screenshots for translators.
• Emails: order confirmation, password reset, shipping updates.
• Raw keys that leaked into the UI, like checkout.cta.label.
• Third-party widgets, such as the payment form or the cookie banner, that follow the browser language instead of your store's.

2. Currency and number formats

A German shopper expects 1.000,50 €. An American expects $1,000.50. Check:

• The currency symbol and its position.
• Thousand and decimal separators, everywhere a price appears, including the cart and the confirmation email.
• That each country gets the right price list, and the right tax display if prices include VAT in one market and not another.

3. Dates and times

Is 04/10 the 4th of October or April 10th? It depends on who's reading. Delivery estimates, order history and booking calendars are where this matters most. Also check that week starts and time formats (24-hour or AM/PM) match the market.

4. Address and phone forms

Address forms are often built for one country. Check that postcodes from each market validate, that "state" isn't required where there are no states, and that phone fields accept international numbers. A shopper who can't enter their own address can't buy anything.

5. Layouts that break with longer words

German and French text often runs noticeably longer than the English it replaced. Look for:

• Buttons where the label overflows or gets cut off.
• Navigation that wraps onto two lines and pushes content down.
• Labels that wrap onto prices or icons.
• Mobile screens, where there's no spare room to begin with.

Then run the whole flow, per locale

Checking pages one by one misses the handoffs, like the currency that resets after a payment redirect. Once the five checks above pass, run your key flow end to end in each language you sell in: browse, add to cart, check out, read the confirmation email.

If you use a translation management system like Lokalise, this is the step it doesn't do. Those tools manage strings and help translators with context; they don't open your store and try to buy something. We explain the difference in more detail on our localization testing page.

With Testavi, you write that flow once in plain English, with checks like "verify all visible text is in German" and "verify prices use € with a comma as the decimal separator", and run it for every market. It pairs naturally with a checkout testing checklist. Our free 30-day pilot is the easiest way to try it on your own store.