UploadFile on Android returns a wrong server response

[ov77]

Bug Report

Capacitor Version

1.0.5

   Capacitor Doctor  💊 

Latest Dependencies:

  @capacitor/cli: 7.4.3
  @capacitor/core: 7.4.3
  @capacitor/android: 7.4.3
  @capacitor/ios: 7.4.3

Installed Dependencies:

  @capacitor/android: 7.4.3
  @capacitor/cli: 7.4.3
  @capacitor/core: 7.4.3
  @capacitor/ios: 7.4.3

[error] Xcode is not installed
[success] Android looking great! 👌

Platform(s)

Android

Current Behavior

Try to upload a file to a server that should return a json response after upload.

const r = await FileTransfer.uploadFile({
    "readTimeout": 2000,
    "connectTimeout": 2000,
    "headers": {
        "X-XXX-Api-Client": "native-mobile",
        "X-XXX-Session": "128b08fb4d606ce2654d6fe2c8bf7868"
    },
    "webFetchExtra": {
        "credentials": "include",
        "keepalive": true
    },
    "url": "http://192.168.4.230:8000/api/v1/temporaryAttachments",
    "path": "file:///data/user/0/com.mydomain.app/cache/ovidiu%40localdomain/drafts-temp-attachments/5349141896_30062a32-d96b-41e6-8755-3996db03564f.pdf",
    "fileKey": "filename",
    "mimeType": "application/pdf"
});

The response looks like:

{ "bytesSent": 93215, "responseCode": "200", "response": "\u001f�\b\u0000\u0000\u0000\u0000\u0000\u0000\u00005��\u000e�0\u0010D�e�T[�]Y���7cL�%�DJ\u0013zQ¿[c<μ7����l��v��Tb*C�\u001e����+�Z���2�\"k:�0W.��\u0006�_�ܡecM��@���ت�4*k\"���Bf\n�FGv>�>6y�1�6|܏\u000f\u0003c���\u0000\u0000\u0000", "headers": "{null=[HTTP/1.1 200 OK], Access-Control-Allow-Credentials=[true], Access-Control-Allow-Headers=[Content-Type, X-Requested-With, Authorization, X-XXX-Session, X-XXX-Api-Client], Access-Control-Allow-Methods=[GET, POST, PUT, PATCH, DELETE, OPTIONS], Access-Control-Allow-Origin=[http://localhost:8100], Access-Control-Expose-Headers=[X-XXX-2FA], Access-Control-Max-Age=[86400], Allow=[GET, POST], Connection=[Keep-Alive], Content-Encoding=[gzip], Content-Length=[139], Content-Type=[application/json; charset=utf-8], Date=[Mon, 8 Sep 2025 07:42:29 GMT], Pragma=[no-cache], Referrer-Policy=[no-referrer], Server=[XXX-Webmail], X-Android-Received-Millis=[1757317349150], X-Android-Response-Source=[NETWORK 200], X-Android-Selected-Protocol=[http/1.1], X-Android-Sent-Millis=[1757317349131]}" }

Expected Behavior

The field response should contain a text representing a JSON object (the server's response).

Code Reproduction

Other Technical Details

I even tried to send a custom value for Accept-Encoding header, but the capacitor always send Accept-Encoding: gzip

I used WireShark to see the call and the response. As you can see the server response looks ok.

Call:

Response:

Additional Context