Translate a Flutter app into Spanish

What Spanish changes in your strings

Spanish UI text runs longer than English. "Settings" becomes "Configuración", "Sign in" becomes "Iniciar sesión". In Flutter, a Text inside a Row or a fixed-width button may overflow, so look for widgets without Flexible, maxLines or overflow.

Questions and exclamations also open with a mark: ¿ and ¡. "Delete this file?" becomes "¿Eliminar este archivo?". If your code builds a question from several fragments, the opening mark ends up in the wrong place. A single string with a placeholder avoids this: "deleteConfirm": "¿Eliminar {fileName}?".

Spanish marks grammatical gender. "welcomeUser": "Welcome, {name}" forces a choice between "Bienvenido" and "Bienvenida". Either add a select message on gender or accept a neutral wording such as "Te damos la bienvenida, {name}". Register matters too: consumer apps usually address the user as tú, while banking or public-service apps often use usted. Whichever you choose, keep it consistent across screens.

ICU plurals: one, many, other

CLDR gives Spanish three plural categories: one, many and other. many covers large round numbers such as a million, where Spanish inserts "de": "1 millón de descargas". In most apps one and other do the heavy lifting, but a complete ICU message covers all three.

Source:

"filesCount": "{count, plural, =0{No files} =1{1 file} other{{count} files}}"

Spanish value:

"filesCount": "{count, plural, =0{Ningún archivo} =1{1 archivo} one{{count} archivo} many{{count} de archivos} other{{count} archivos}}"

Manuce checks the structure of these messages, leaves placeholders exactly as they are ({count} stays {count}) and adds the Spanish plural categories where they are missing. select messages are handled the same way: the selectors male, female and other stay put; only the text in each branch is translated.

Spain or Latin America: organising your files

Common interface words differ: "ordenador" or "computadora", "móvil" or "celular", "vídeo" with an accent in Spain, "video" without one in Mexico. Plural address differs as well: "vosotros" in Spain, "ustedes" in Latin America.

In Flutter, the usual set-up is a generic app_es.arb, plus, if needed, a regional file such as app_es_MX.arb holding only the strings that differ; generation falls back to the es file for everything else. State your audience in the @ key descriptions ("button, Mexican users, informal tú"): Manuce reads them as context.

Formats follow the locale, not the translation: Spain writes 1.234,56 €, Mexico 1,234.56. If a placeholder is declared with a type and format (double as currency, DateTime as yMMMd), Flutter formats it for the active locale, so avoid hard-coding a currency symbol or date in the string itself. Manuce does not translate numbers or date formats, which keeps those declarations intact.

What Manuce returns, and what it does not do

• The same .arb file: indentation, key order, quotes, comments, line endings, encoding and BOM preserved; only the values change.
• @@locale is set to "es".
• @ metadata keys are not translated; their descriptions are used as context.
• Every translated value is compared with the source. If a placeholder or tag goes missing and the mismatch persists, the source value is kept and the report says so.
• Left as they are: keys, empty values, URLs, email addresses, numbers, colours, date formats, identifiers and anything marked as non-translatable.
• A report listing translated strings, strings left unchanged and why.

Manuce does not edit your Dart code, l10n.yaml or Info.plist, and it does not run the app, so it cannot see on-screen overflow. Pricing is based on the words in the values, keys and tags excluded; Spanish is charged at the base rate (×1 coefficient).

Preparing the file and checking it afterwards

1. Start from the complete, up-to-date template file named in template-arb-file.
2. Add descriptions to ambiguous keys: "Open" on a button is "Abrir", "Open" as a shop's status is "Abierto".
3. Replace concatenated fragments with full strings using placeholders, especially for ¿…? questions.
4. Once delivered, save the file as app_es.arb, run flutter gen-l10n and confirm that es appears in AppLocalizations.supportedLocales. For iOS, also declare es in CFBundleLocalizations.
5. Test narrow screens and plurals with 0, 1, 2 and one million.

Finally, read the report: any string left in the source language is explained there, for instance a placeholder not found in the translation or a value marked as non-translatable.

In practice

1. Upload your template .arb file (app_en.arb or your source language).
2. Check the instant quote and the free Spanish sample.
3. Download the translated file and the string report.
4. Save it as app_es.arb, run flutter gen-l10n and test your screens.