When the User-Agent includes “YJApp-IOS jp.co.yahoo.○○○○”, it indicates that the page was opened inside the Yahoo JAPAN App’s built‑in iOS browser. This is different from Safari and uses Yahoo’s own WebView.
Conclusion
If this identifier appears in the User-Agent, the traffic source is the Yahoo JAPAN app. This applies to search results, news feeds, and Yahoo Ads.
Why This Matters
The identifier is automatically attached when the Yahoo app opens a web page. Because of this, it provides a reliable way to understand where users came from and which app environment displayed your pages.
How It Works
Example User-Agent:
Mozilla/5.0 (iPhone; CPU iPhone OS 18_6_2 like Mac OS X)
AppleWebKit/605.1.15 (KHTML, like Gecko)
Mobile/15E148 Version/18.6.2
YJApp-IOS jp.co.yahoo.ipn.appli/4.151.0
Key identifiers:
- YJApp-IOS → Yahoo App for iOS
- jp.co.yahoo.ipn.appli/ → App-level identifier
- 4.151.0 → App version
With these present, you can confidently determine that the access came through the Yahoo App.
Optimization Tips
Traffic from the Yahoo App can strengthen your presence in Yahoo Search and the in-app recommendation system. Effective actions include:
- Keeping titles around 32 characters for Yahoo’s display style
- Optimizing mobile page speed
- Applying Safari-compatible CSS, as Yahoo App users skew heavily toward iPhone
This traffic source functions like Yahoo’s version of “Discover,” so optimizing for it can help stabilize overall blog traffic.
参考URL（Research Sources）
- Yahoo! JAPAN アプリ公式解説（User-Agent仕様確認） https://developer.yahoo.co.jp/webappli/guide/
- Apple WebView 技術情報（WKWebView仕様） https://developer.apple.com/documentation/webkit/wkwebview/
- Yahoo!広告ヘルプ（アプリ内ブラウザ挙動） https://ads-help.yahoo.co.jp/yahooads/
