UI extensions no longer have a 256 KB limit on the combined size of their locale files. As of October 30, 2026, you can add more languages to an extension without hitting a combined size limit at deploy. This applies to all apps with UI extensions, and no action is required.
What changed
Previously, the total size of the locale files in a UI extension's locales folder couldn't exceed 256 KB. Extensions with many languages could reach that limit and fail to deploy, which forced you to trim translations or drop languages.
That combined limit is now removed. The 30 KB limit for each individual locale file still applies. Locale files keep the same format, file naming, and fallback behavior described in the checkout UI extension localization guide. You don't need to change how you structure translations.
Who's affected
This change applies to every app that includes UI extensions with locale files, on all API versions. Existing extension versions keep working as before. New deploys aren't limited by the combined size of locale files.
If your extensions were under the old limit, nothing changes for you.
What to do
You don't need to take any action. If you previously removed languages or shortened translations to stay under 256 KB, you can add them back:
- Add the locale files you need to your extension's
localesfolder, for examplede.jsonorpt-BR.json. Keep each file under 30 KB. - Run
shopify app deployto release a new app version. - Preview the extension in a development store with the store or customer locale set to one of the new languages, and confirm the translated strings appear.