[cft]

Messages are not deleted from the server. They are probably stored there in the encryped form. When I open the web version of WhatsApp, same images and the message history that i have on my phone get downloaded there. I highly doubt that they rely on my phone as the only master storage of that data and upload all images into the web version from it?

[ars]

Actually yes, that is exactly what they do: Download everything from the phone.

[cft]

Including 2MB images in the conversation? Has someone verified this by looking at the traffic?

[Spare_account]

My experience of WhatsApp Web has been that the images do not auto-load (Chrome on Windows 10 and Windows 7). A heavily compressed thumbnail is loaded and I have to manually click each image that I want to view.

I haven't analysed any traffic and I'm not a developer but my layman's guess would be that the WhatsApp mobile app has a pre-prepared Zip file (or some other compressed container) with the 20 most recent messages from each chat plus these compressed image thumbnails and the Web Client pulls that data from the phone upon initialising. I doubt it is a big data transfer.

[cft]

Actually, the "latest" images (whatever it means) auto-load. Only when you go up in the history you have to click to load.

[fastball]

I hadn't, but now I have.

Using mitmproxy to snoop my phone, I see that all the data coming into my computer when I open up Whatsapp Web is originating from my phone. Including pictures.

That being said, all of my current conversations are on the new "end-to-end-encryption" thing, which might make a difference.

[ergl]

Images and videos are stored on their server for a fixed amount of time, and deleted afterwards. (So you just send an url and the client transforms it into a thumbnail).

You can test this by trying to download an image for the first time after a few weeks, it will tell you that the image is no longer available, and you should ask the other recipient to send it again.

[nindalf]

I can't answer that question but I can say that images shared with whatsapp are compressed to < 100kb

[cft]

That's not true: I just looked in my WhatsApp gallery, the first image I opened was 525KB. At <100KB, any screenshot of text would show visible compression distortion around the letter edges, which they do not.

[nitin_flanker]

I guess no. I uses mobile data to access whatsapp on phone. My chat history is roughly more than 250 MB.

The time Whatsapp web takes to download images and messages is far way faster than my actual 2G network on phone.

[cosecantt]

I think you should try web app disabling the internet on your phone. Have you tried it? If watsup store the messages on its servers, it would be able to retrieve. But this is also not reliable since they may check phone connectivity before they retrieve from their "servers". I am still skeptical that they may store on servers behind the scene at least for speed and performance.

[squeaky-clean]

I just opened the Whatsapp web app (never used it before), and then immediately set Airplane Mode on my phone as soon as it scanned the QR code.

WhatsApp managed to load all my conversations (I don't have many) and the most recent message, for display in the list-view. But each conversation only has the most recently sent message. After a while I got a "Phone Not Connected" message. Seems like it really is only stored on your phone.

[nitin_flanker]

>they may store on servers behind the scene at least for speed and performance.

Yes, that's why I think so. They easily loads all the messages and images in just few seconds even when my phone's internet is too slow.

They won't let you use the web app when you're phone is disconnected, so there's no way to confirm it.

[fastball]

In order to use Whatsapp Web you need to be on the same wifi network as your phone.

Your phone has the data on it. Intranet speeds on most wifi networks these days is faster than 50Mbps. That's more than fast enough to transfer all your messages and photos with little to no lag.

It doesn't matter how fast your connection to the WWW is because you're not using the WWW to transfer the data, you're using the wifi intranet.

[squeaky-clean]

It will work over a mobile connection, using wifi is only recommended to save data usage.

[fastball]

In order to use Whatsapp Web, your computer/tablet and your phone need to be connected to the same wifi network.

That makes it easy to send all the data necessary from your phone to your computer in the blink of an eye, because intranet wifi speeds are very fast.

On my iPhone, backups can be stored, but through iCloud, not on Whatsapp servers.