Translation File Formats Comparison: JSON vs YAML vs Properties vs XLIFF vs PO

Translation File Formats Comparison

Choosing the right file format for translations affects tooling compatibility, translator workflow, and developer experience. Here is a comprehensive comparison of the five most common formats.

JSON

{
  "common": {
    "buttons": {
      "submit": "Submit",
      "cancel": "Cancel"
    }
  }
}

Used by: react-i18next, next-intl, vue-i18n, Angular, most JavaScript frameworks Pros: Native to JavaScript, supports nesting, widely supported by TMS tools Cons: No comments, strict syntax (trailing commas forbidden), verbose for flat keys

YAML

common:
  buttons:
    submit: Submit
    cancel: Cancel

Used by: Ruby on Rails, Ansible, Kubernetes configs, Spring Boot (optional) Pros: Compact, supports comments, human-readable Cons: Whitespace-sensitive, type coercion gotchas (NO becomes boolean), less tooling for i18n

Java Properties

common.buttons.submit=Submit
common.buttons.cancel=Cancel

Used by: Spring Boot, Java EE, Android (partially) Pros: Simple key=value format, native Java support, no nesting complexity Cons: No nesting, no data types, special character escaping required, ASCII-only (use \uXXXX for Unicode)

XLIFF (XML Localization Interchange File Format)

<trans-unit id="common.buttons.submit">
  <source>Submit</source>
  <target>Enviar</target>
</trans-unit>

Used by: iOS (Xcode), Angular (optional), enterprise TMS tools Pros: Industry standard (OASIS), rich metadata (notes, state, context), supported by all professional TMS Cons: Verbose XML syntax, overkill for small projects, harder to edit manually

PO/Gettext

#: common.buttons.submit
msgid "Submit"
msgstr "Enviar"

Used by: Django, Flask, WordPress, PHP frameworks, GNU projects Pros: Mature ecosystem, supports pluralization natively, comments and context, many free tools (Poedit, Weblate) Cons: Not natively supported by JavaScript frameworks, flat structure only

Format Comparison Table

Feature	JSON	YAML	Properties	XLIFF	PO
Nesting	Yes	Yes	No	No	No
Comments	No	Yes	Yes	Yes	Yes
Plurals	Library	Library	No	Yes	Yes
TMS support	Good	Fair	Good	Excellent	Good
Human editing	Good	Good	Good	Poor	Good
JS ecosystem	Excellent	Good	Poor	Fair	Fair

Which Format to Choose?

• JavaScript / TypeScript projects -- JSON (nested)
• Ruby / Python projects -- YAML or PO
• Java / Android projects -- Properties
• Enterprise with professional translators -- XLIFF
• CMS / WordPress -- PO/Gettext