We can use axios for this purpose as below

1. First we need to define User-Agent request header for desktop and mobile devices. Here I’m using a isMobile as a dummy flag which you can pass in your function:

   const headers = {
       'User-Agent': isMobile
           ? 'Mozilla/5.0 (Windows NT 10.0; Android 13; SM-G981B) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Mobile Safari/537.36'
           : 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36' ,
       'Accept-Encoding': 'gzip, deflate, br'
   }
   

2. Then we can use axios to get the page size as below:

   const response = await axios.get(url, {
       headers, 
       responseType: 'arraybuffer', 
       validateStatus: () => true,
       decompress: false,
   }); 
   const sizeInBytes = response.data.length; 
   const encoding = response.headers['content-encoding'] || 'none';
   

Note:

1. You can use the response header content-length to get the page size but there are many cases when this header is not provided by the server, hence I have used a response type of arraybuffer and calculated the length of the buffer.
2. if you don’t use the decompress: false flag then axios/node will by default decompress the response and also you content-encoding header will not be present due to which you won’t be able to identify the encoding type.