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The search_language_filter parameter allows you to filter search results by language using ISO 639-1 language codes. Only results in the specified languages will be returned.
Language codes must be valid 2-letter ISO 639-1 codes (e.g., “en”, “ru”, “fr”). You can filter by up to 10 languages per request.

Overview

The language filter for the Search API allows you to control which search results are returned by limiting them to specific languages. This is particularly useful when you need to:
  • Search for content in specific languages
  • Conduct multilingual research across multiple languages
  • Focus on regional content in local languages
  • Build language-specific applications or features
The search_language_filter parameter accepts an array of ISO 639-1 language codes and returns only results that match those languages. To filter search results by language:
This filter will be applied in addition to any other search parameters.

Examples

1. Single Language Filter This example limits search results to English language content only. Request Example
2. Multiple Language Filter Search across multiple languages to gather diverse perspectives or multilingual content:
3. Regional Language Search Focus on content from specific regions by using their local languages:
4. Combining with Other Filters Language filters work seamlessly with other search parameters for precise control:

Parameter Reference

search_language_filter

  • Type: Array of strings
  • Format: ISO 639-1 language codes (2 lowercase letters)
  • Description: Filters search results to only include content in the specified languages
  • Optional: Yes
  • Maximum: 10 language codes per request
  • Example: "search_language_filter": ["en", "fr", "de"]

Common Language Codes

Here’s a comprehensive list of frequently used ISO 639-1 language codes:
For a complete list of ISO 639-1 language codes, see the ISO 639-1 standard.

Best Practices

Language Code Validation

  • Use Valid Codes: Always use valid 2-letter ISO 639-1 codes. Invalid codes will result in an API error.
  • Lowercase Only: Language codes must be lowercase (e.g., “en” not “EN”).
  • Client-Side Validation: Validate language codes on the client side using a regex pattern:

Strategic Language Selection

  • Be Specific: Choose languages that are most relevant to your research or application needs.
  • Consider Your Audience: Select languages that match your target audience’s preferences.
  • Regional Relevance: Combine language filters with geographic filters (country parameter) for better regional targeting.
  • Content Availability: Some topics may have limited content in certain languages. Start broad and narrow down as needed.

Performance Considerations

  • Filter Size: While you can specify up to 10 languages, using fewer languages may improve response times.
  • Result Quality: More languages mean a broader search scope, which can dilute result relevance. Be strategic about which languages to include.
  • Combination Effects: Language filters combined with other restrictive filters (domain, date) may significantly reduce the number of results.

Advanced Usage Patterns

Multilingual Research

Conduct comprehensive research by searching across multiple languages:

Content Localization Research

Find examples and references in target languages for localization projects:

Academic Research Across Languages

Access scholarly content in different languages:

News Monitoring by Language

Track news stories across different language regions:

Error Handling

When using language filters, implement proper error handling for validation issues:
For best results, combine language filtering with other filters like search_domain_filter or search_recency_filter to narrow down your search to highly relevant, timely content in your target languages.