Inside glow on textfield in flutter

You are trying to add inner shadow with blur. Use BoxDecoration in Container and tweak spreadRadius and blurRadius as per your need.

Container(
            decoration: BoxDecoration(
              boxShadow: [
                BoxShadow(
                  color: Colors.blue[500]!,
                ),
                BoxShadow(
                  color: Colors.blue[900]!,
                  spreadRadius: -5.0,
                  blurRadius: 5.0,
                ),
              ],
            ),
            child: TextField(
              obscureText: true,
              decoration: InputDecoration(
                border: OutlineInputBorder(),
              ),
            ),
          ),