Validate Translation

Validate that a translated string meets quality requirements and preserves required elements from the original.

Inputs

• original_text: The original English text
• translated_text: The translated text to validate
• target_language_code: ISO language code (e.g., es, fr, de)

Output

Return a validation result object:

{
  "valid": true,
  "issues": [],
  "warnings": []
}

Or with problems:

{
  "valid": false,
  "issues": [
    "Missing placeholder: {{name}}"
  ],
  "warnings": [
    "Translation is 2.8x longer than original"
  ]
}

• valid: false if any blocking issues exist, true otherwise
• issues: Blocking problems that must be fixed (array of strings)
• warnings: Non-blocking concerns to review (array of strings)

Validation Checks

1. Placeholder Preservation (Blocking)

Extract all placeholders from the original text and verify they exist in the translation.

Placeholder patterns to check:

Pattern	Regex	Example
Double braces	\{\{[\w.]+\}\}	{{name}}, {{user.email}}
Single braces	\{[\w]+\}	{count}, {0}
Dollar braces	\$\{[\w]+\}	${total}
Printf style	%[sd]	%s, %d
Percent braces	%\{[\w]+\}	%{count}
Double brackets	\[\[[\w]+\]\]	[[user]]
Numbered tags	<\d+>	<0>, <1>

Checks:

• All placeholders from original must appear in translation
• No extra placeholders should be added
• Placeholder syntax must be preserved exactly (e.g., {{name}} not {name})

Issues (blocking):

• "Missing placeholder: {{name}}"
• "Extra placeholder in translation: {{unknown}}"
• "Placeholder syntax modified: {{name}} changed to {name}"

2. Empty or Whitespace (Blocking)

Check that the translation is not empty or only whitespace.

Issue (blocking):

• "Translation is empty or whitespace only"

3. Untranslated Markers (Blocking)

Check for common markers indicating incomplete translation.

Patterns to detect:

• TRANSLATE_ME
• TODO
• [TODO]
• FIXME
• XXX
• UNTRANSLATED
• NEEDS_TRANSLATION
• TBD

Issue (blocking):

• "Contains untranslated marker: [TODO]"

4. Still in English Check (Warning)

Perform a basic check to see if the text might still be in English when it shouldn't be.

Logic:

• If original and translated are identical AND original has 3+ words
• AND target language is not English
• This suggests the text wasn't translated

Warning:

• "Translation appears identical to English original"

Exceptions (do not warn):

• Single words (might be proper nouns, technical terms)
• URLs, email addresses, technical identifiers
• Text that's mostly placeholders

5. Length Ratio Check (Warning)

Compare the length of translation to original.

Acceptable ratios by language family:

Language	Min Ratio	Max Ratio	Notes
German (de)	0.8	1.5	Compound words, but efficient
French (fr)	0.9	1.4	Slightly longer than English
Spanish (es)	0.9	1.4	Slightly longer than English
Italian (it)	0.9	1.4	Similar to Spanish
Portuguese (pt)	0.9	1.4	Similar to Spanish
Russian (ru)	0.8	1.5	Cyrillic, varies
Chinese (zh)	0.3	0.8	Much more compact
Japanese (ja)	0.4	1.0	More compact
Korean (ko)	0.5	1.0	More compact
Arabic (ar)	0.8	1.4	Varies
Hebrew (he)	0.7	1.2	Generally shorter
Hindi (hi)	0.9	1.5	Can be longer
Thai (th)	0.8	1.3	Generally similar
Default	0.5	3.0	Permissive fallback

Warning:

• "Translation is unusually short (0.3x original length)"
• "Translation is unusually long (2.5x original length)"

Exceptions (skip check):

• Original is less than 10 characters
• Text is mostly placeholders
• Single word translations

6. Character Encoding (Blocking)

Check for encoding issues.

Patterns to detect:

• Replacement character: � (U+FFFD)
• Mojibake patterns: é instead of é
• Null characters: \x00
• Control characters (except \n, \t)

Issue (blocking):

• "Contains invalid character encoding (replacement character found)"
• "Contains suspicious encoding pattern (possible mojibake)"

7. HTML/Entity Preservation (Warning)

If original contains HTML entities, check they're preserved or properly converted.

Entities to check:

•  , &, <, >, ", &#...;

Warning:

• "HTML entity   in original not found in translation"

8. Newline/Formatting Preservation (Warning)

Check that structural formatting is preserved.

Check:

• If original has \n, translation should have \n
• If original has leading/trailing whitespace, translation should match

Warning:

• "Original has newlines but translation does not"
• "Original has trailing punctuation but translation does not"

Severity Classification

Blocking Issues (valid = false)

• Missing placeholders
• Extra placeholders
• Modified placeholder syntax
• Empty translation
• Untranslated markers
• Invalid character encoding

Warnings (valid = true, but review recommended)

• Identical to English
• Unusual length ratio
• Missing HTML entities
• Formatting differences

Examples

Valid Translation

Input:
  original_text: "Hello {{name}}, you have {{count}} messages."
  translated_text: "Hola {{name}}, tienes {{count}} mensajes."
  target_language_code: "es"

Output:
  {
    "valid": true,
    "issues": [],
    "warnings": []
  }

Missing Placeholder

Input:
  original_text: "Welcome {{name}}!"
  translated_text: "¡Bienvenido!"
  target_language_code: "es"

Output:
  {
    "valid": false,
    "issues": ["Missing placeholder: {{name}}"],
    "warnings": []
  }

Untranslated

Input:
  original_text: "Save changes"
  translated_text: "Save changes"
  target_language_code: "de"

Output:
  {
    "valid": true,
    "issues": [],
    "warnings": ["Translation appears identical to English original"]
  }

Multiple Issues

Input:
  original_text: "Delete {{count}} items permanently"
  translated_text: "[TODO] Supprimer {count} éléments"
  target_language_code: "fr"

Output:
  {
    "valid": false,
    "issues": [
      "Contains untranslated marker: [TODO]",
      "Placeholder syntax modified: {{count}} changed to {count}"
    ],
    "warnings": []
  }

Length Warning

Input:
  original_text: "OK"
  translated_text: "De acuerdo, entendido"
  target_language_code: "es"

Output:
  {
    "valid": true,
    "issues": [],
    "warnings": ["Translation is 10.5x longer than original"]
  }

Implementation Notes

1. Be permissive: Languages vary significantly. When in doubt, warn rather than block.

2. Context matters: A translation that seems "wrong" might be intentional (e.g., adapting idioms).

3. Placeholder order: Placeholders may legitimately be reordered for grammar. Only check presence, not position.

4. Case sensitivity: Placeholder names are case-sensitive. {{Name}} ≠ {{name}}.

5. Whitespace in placeholders: {{ name }} ≠ {{name}}. Treat as different placeholders.