The file tag is using a private api of web view in Android system and Google has removed it in Android 4.4. However, in Android 5 they bring it back. So UniWebView supports the "input" tag (something like
<input type="file" name="file" id="file">) and file chooser except Android 4.4.
Unfortunately, it seems that there is no solution for Android 4.4 now. UniWebView could work well with file chooser in Android 4.3 or below, and Android 5.0 or above, but not 4.4. So we guess you may need to do some restriction in your webpage for Android 4.4 users on this. We are very sorry about it.