When you ask an AI agent something in Korean or Spanish, does it search in that language? I ran 320 web-search sessions with Claude Code (Opus 5.5) and Codex CLI to find out.
Global topic (AI products), asked in Korean, Japanese, Spanish or Ukrainian:
- 205 of 206 searches were in English.
- 0 of the 222 cited pages were in the question's language.
Local topic (metro fare, this week's news, restaurants in Seoul, Tokyo, Madrid, Kyiv), 5 runs per question:
| Claude Code | Codex | |
|---|---|---|
| Asked in the local language: searches in that language | 82% | 50% |
| Asked in English: searches in the local language | 49% | 17% |
- Asked in English about Tokyo, Codex searched in Japanese 1 time out of 56.
- Madrid was the exception for both: even in English, most cited pages were Spanish (Claude 42 of 53, Codex 26 of 31).
- Asked in Ukrainian for Ukraine's news, all 15 links Codex cited were English-language outlets.
- All 320 answers came back in the language of the question, so you usually can't tell from the answer which language the sources were in.
Why it matters: if you publish in a language other than English, AI agents may only find you for local topics. For global topics, the English web wins.
Every query, cited URL and the language of each cited page are in the dataset (CSV/JSON, CC BY 4.0): https://tokensave.app/data/claude-web-search-by-language
Top comments (0)