Multi-Language User Research: How to Interview Participants in Any Language

Most research teams run their user interviews in English — even when their customers are not. The result is systematic blind spots: non-English-speaking markets receive less research, their needs are underrepresented in product decisions, and entire customer segments become invisible in qualitative data.

AI-powered interview platforms like Koji change the economics of multilingual research. Instead of hiring bilingual moderators, coordinating cross-timezone sessions, or outsourcing translation, teams can run voice and text interviews in 15+ languages with the same quality, depth, and automated analysis they get from English-language studies.

This guide covers how to set up multilingual studies in Koji, best practices for cross-language research, and how to synthesize findings across language groups.

Why Multilingual Research Matters

The business case for multilingual research is clear:

• 51% of internet users prefer content in their native language (W3Techs), and this preference extends strongly to research participation
• Non-English speakers are consistently underrepresented in qualitative research, even at global companies with international customer bases
• Critical cultural nuances — how users describe problems, what emotional language they use for pain points, how they frame success — get lost when participants are interviewed in a second language
• GDPR and data localization requirements make European market research increasingly important for any team selling into the EU

Traditional barriers to multilingual research are real: hiring bilingual moderators costs 2–4x standard rates, translation workflows add 1–2 weeks to research timelines, and most analysis tools struggle with non-English transcripts. Platforms like Koji eliminate all three barriers by running the entire interview workflow natively in the target language.

Languages Supported

Koji's AI interviewer supports the following languages in voice mode:

• English (US, UK, Australian)
• Spanish (Latin American and Castilian)
• French
• German
• Dutch
• Japanese
• Hindi
• Portuguese (Brazilian and European)
• Italian
• Polish
• Turkish
• Korean
• Mandarin Chinese
• Arabic
• Swedish

Text mode supports all of the above plus dozens of additional languages through Google Gemini's multilingual capabilities — covering virtually all major world languages.

When you set a language on your study, Koji automatically:

1. Generates the AI interviewer's system prompt in that language
2. Selects an appropriate native-speaker voice profile (voice mode)
3. Configures speech-to-text transcription for that language
4. Translates the interview UI, buttons, and participant-facing instructions

Setting Up a Multilingual Study

Option A: Single-Language Study

If all your participants speak the same language, create one study and set the language in Customize → Interaction Mode → Default Language.

Steps:

1. Create a new study in Koji
2. Describe your research goal in the target language — Koji's AI will generate the brief in that language
3. Go to Customize → Interaction Mode
4. Set Default Language to your target language (e.g., Spanish, French, German)
5. Update your landing page headline and description in the same language
6. Run a test interview to verify the AI speaks naturally
7. Launch and share your interview link with your target participants

Pro tip: Write your research brief in the same language as the interview. The AI uses your brief as its source of truth. A brief written natively in Spanish produces more natural Spanish interview flow than an English brief that the system has to bridge across languages.

Option B: Multi-Market Study with Separate Links

For research spanning multiple language markets, the recommended approach is to create one study per language. This gives you:

• Clean, separate data per language for market-by-market analysis
• Language-specific landing pages with culturally appropriate copy
• Separate transcript analysis per language group
• Cleaner report generation per market with no cross-language noise

Setup:

1. Create your base study in your primary language
2. Create a duplicate study for each additional language
3. Set the language for each duplicate in the Customize tab
4. Customize each landing page in the appropriate language
5. Distribute language-specific interview links to the right audiences

You can import participants for each language study via CSV, and personalized links will take each participant directly to the correct language study. See Importing Participants via CSV for the import workflow.

Option C: Language Parameter in the URL

For embed or in-product use cases where you know a user's locale, you can pass a language parameter in the interview URL to override the default:

• koji.so/i/your-study?lang=es → Spanish interview
• koji.so/i/your-study?lang=fr → French interview
• koji.so/i/your-study?lang=de → German interview

This is particularly useful when embedding Koji in your product — you can detect the user's locale and pass the appropriate ?lang= parameter so they always receive the interview in their language without needing separate studies.

Writing Research Briefs for Multilingual Studies

The research brief is the most important document in any Koji study. For multilingual work, a few additional considerations apply:

Localize your brief, do not just translate it. Direct translation of English research questions often sounds unnatural in other languages. Idioms, phrasing, and conceptual framing vary significantly across languages and cultures. Where possible, use Koji's AI assistant to generate the brief natively in the target language, or have a native speaker review the translated brief before launch.

Be explicit about cultural context. If you are researching a behavior that differs across cultures — how different markets approach financial decisions, privacy expectations, or relationship-driven buying behavior — add that context to the Problem Context section of your brief.

Consider formality register. Several languages have formal and informal registers: Japanese (keigo vs. casual), German (Sie vs. du), French (vous vs. tu), Korean (formal vs. informal speech levels). Specify the appropriate register in your brief. B2B research in Japanese typically requires formal keigo; consumer research for a younger demographic may be more casual.

Localize screening questions. Intake form fields and screening questions should be in the local language. A French participant filling out an English screening form has a worse experience and may provide less accurate responses.

Analyzing Multilingual Results

Transcripts in Native Language

All transcripts in Koji are captured in the original interview language. If you run a Spanish study, you will see Spanish transcripts. AI analysis — quality scores, themes, sentiment, insights — is generated in the same language as the interview.

Cross-Language Synthesis

For research spanning multiple language markets, Koji's report generation can synthesize findings across studies. When you generate a report that draws on multiple studies, the AI identifies common themes across language groups and surfaces market-specific differences.

For more targeted cross-language comparison, use the AI Consultant in your Insights Dashboard:

• "What themes appeared in the German study but not the French study?"
• "Are the same pain points appearing consistently across all markets?"
• "How do Japanese participants describe this problem differently from US participants?"

English Summaries from Non-English Research

If your primary working language is English but your participants are not, you can request that Koji generate report summaries and executive findings in English even when the underlying transcripts are in other languages. Configure this preference at the report generation stage.

This workflow is common for global research teams: run interviews natively in local languages for authentic responses, then synthesize and report in English for internal stakeholders.

Use Cases for Multilingual Research

International market expansion: Before entering a new market, run discovery interviews with potential customers in their native language. Understand their current alternatives, pain points, and buying criteria without the filter of a second language distorting your data.

Localization validation: After translating your product or marketing materials, interview users in the local language to verify whether the translation resonates naturally or sounds awkward and foreign.

Global employee research: For organizations with international workforces, run employee experience research in employees' native languages. Non-English speakers are consistently underrepresented in HR, culture, and engagement research — with significant consequences for team health and retention.

Multilingual customer feedback programs: Build a continuous research pipeline that automatically interviews customers in their language after key touchpoints (onboarding, support interactions, renewals), then synthesizes findings across markets for product and strategy decisions.

Academic and institutional research: For research institutions studying cross-cultural phenomena, Koji enables standardized interview protocols to be deployed across multiple language markets simultaneously, with consistent methodology and comparable data quality.

Audio Quality Tips for Non-English Voice Interviews

Voice interview quality varies somewhat by language. A few practical notes:

• Test each language before launch. Run a self-test interview in the target language to verify naturalness of speech and appropriateness of the voice profile.
• Some accents and dialects may reduce transcription accuracy. For highly regional accents, enabling text mode as a fallback is prudent.
• Encourage headphones. This applies universally — headphones improve audio quality in any language.
• Consider time zones when monitoring. If you are watching response rates in real time, remember that your participants across different markets may be active at very different hours.

Getting Started with Multilingual Research

To run your first non-English study in Koji:

1. Create a new study and describe your research goal in the target language
2. Set the language in Customize → Interaction Mode → Default Language
3. Write your landing page headline and intake form in the target language
4. Run a test interview to verify the AI sounds natural and covers your research topics
5. Share your language-specific link with your target participants

With tools like Koji, multilingual research is no longer a specialized, resource-intensive effort reserved for large enterprise research teams. It is a standard capability available to any team that cares about understanding customers wherever they are in the world.