Translate Java
Properties Files
Upload your .properties files, translate values while keeping interpolation and comments intact, and export a file your JVM app loads without changes.
# Polish
user.hello=Witaj, {0}
login.title=Zaloguj się
login.email=Adres e-mail
login.password=Hasło
login.button=ZalogujWhy teams use Java Properties for translations
Each line pairs a key and a value with an equals sign, comments start with #, and one file holds one language, typically named like messages_pl-PL.properties. Java's standard library reads the format natively, so there is no parsing step at runtime.
Dynamic values use {0} positional interpolation, or named parameters like {name}, both read and written back exactly as they were.
Properties messages = new Properties();
messages.load(
new FileInputStream("messages_en.properties")
);Beyond key and value
What SimpleLocalize keeps from your properties files
Automatic character escaping
Tabs, newlines, # and = are escaped on export and unescaped on import by default.
Spring Boot quote handling
Optional options keep single quotes safe with Spring's MessageSource, so MessageFormat parsing doesn't break.
UTF-8 by default
Files are encoded in UTF-8, matching the default Java has used since Java 9.
Interpolation preserved
Positional {0} and named {name} placeholders stay intact through auto-translation.
End-to-end workflow
Translate a properties file end to end
Upload a source messages_en.properties file, translate values while keeping interpolation intact, and download one file per language.
simplelocalize upload \
--apiKey PROJECT_API_KEY \
--uploadFormat java-properties \
--uploadPath ./messages_en.propertiesUpload your source properties file
1messages_en.properties to SimpleLocalize with the CLI. Comments and {0} / {name} interpolation import as-is.simplelocalize download \
--apiKey PROJECT_API_KEY \
--downloadFormat java-properties \
--downloadPath ./messages_{lang}.properties \
--downloadOptions ESCAPE_SINGLE_QUOTESKeep Spring Boot's MessageSource happy
2MessageSource, add ESCAPE_SINGLE_QUOTES on export (and UNESCAPE_SINGLE_QUOTES on import) so quotes survive MessageFormat parsing.user.hello=Witaj, {0}
login.title=Zaloguj sięAuto-translate every language
3simplelocalize download \
--apiKey PROJECT_API_KEY \
--downloadFormat java-properties \
--downloadPath ./messages_{lang}.propertiesDownload one file per language
4messages_{lang}.properties, ready to drop next to your existing bundles with no renaming step.UTF-8 by default, XML on request
Java Properties files historically used ISO-8859-1 encoding, limited to a small character set. Since Java 9, the default changed to UTF-8, and SimpleLocalize encodes every properties file in UTF-8 to match. If your app still expects the older default, set the encoding explicitly.
A lesser-known option: *.properties content can also be represented as XML, using a <properties> root and one <entry> per key, still loadable through Java's native Properties class.
<?xml version="1.0" encoding="utf-8"?>
<properties>
<entry key="hello-world">Witaj Świecie</entry>
<entry key="sign-in">Zaloguj się</entry>
</properties>For developers
A localization platform,
Spring Boot included
The details that break a hand-edited properties file are handled automatically on import and export.
Automatic character escaping
Special characters like tabs, newlines, # and = are escaped on export and unescaped on import, by default.
Spring Boot quote handling
Optional import and export options keep single quotes safe with Spring's MessageSource, so MessageFormat parsing doesn't break.
AI auto-translation
Translate new and changed messages with DeepL, Google Translate, OpenAI, Claude or Gemini.
CLI and REST API
Upload and download properties files from the CLI, or automate the same logic through the REST API.
Every JVM language
Where Java Properties is used
Read natively by every JVM-based language, and used for configuration as well as translations.
Java
Spring Boot
Play Framework
Micronaut
libGDX
Quarkus
Android
Scala
Kotlin
Groovy
Not the only option
Alternatives to Java Properties
Property files are the JVM default, but SimpleLocalize supports the same project in any of these formats too.
More conversions
Convert Java Properties to other formats
Free online converter, no account required. Upload a .properties file and download it in the format you need.
Start translating Java Properties files
- Character escaping and Spring Boot quote handling built in
- UTF-8 by default, one file per language
- Auto-translation with DeepL, Google, OpenAI, Claude and Gemini
"The product
and support
are fantastic."
"The support is
blazing fast,
thank you Jakub!"
"Interface that
makes any dev
feel at home!"
"Excellent app,
saves my time
and money"
Resources
See the latest news from our blog, including product updates, tutorials, and more.
Java Internationalization: Java 21, Java 25 LTS, and Java 26
A practical guide to Java internationalization across LTS versions. Learn how Locale, ResourceBundle, DateTimeFormatter, and number formatting work in Java 21, Java 25 LTS, and Java 26.
Spring Boot 3.5: Internationalization (i18n) with messages.properties
Learn how to implement internationalization in Spring Boot 3.5 application. Translate page and email using message.properties files, Thymeleaf templates, LocaleResolver, and more.
Frequently asked questions about Java properties files
Are special characters escaped automatically?
Yes. Characters like \t, \n, \r, \f, backslash, # and = are escaped on export and unescaped on import by default, with no configuration needed.
How do I keep single quotes working with Spring's MessageSource?
Add the ESCAPE_SINGLE_QUOTES export option (and UNESCAPE_SINGLE_QUOTES on import) so single quotes survive MessageFormat parsing, and remember to set alwaysUseMessageFormat to true in your bean configuration.
What encoding does SimpleLocalize use?
UTF-8, matching the default Java has used since Java 9. Older ISO-8859-1 based projects should set their encoding explicitly if they haven't migrated.
Which frameworks use Java properties for translations?
Any JVM-based application: Java, Spring Boot, Kotlin, Scala and Groovy projects, plus tools like the Thymeleaf template engine, all read translations from .properties files.