You can actually send a message without saving a contact. Using WhatsApp's click to chat:

  wa.me/263xxxxxxxxx?text=Hello

Note: The phone number with country code and no preceding plus.

Opening that link will launch WhatsApp (or WhatsApp web) to the user's number and the text "Hello" in the message field.

On Chrome Desktop Linux, it doesn't work despite me being logged into whatsapp web. Tries to do some xdg-open thing, but clearly that will never work considering whatsapp web has no registered protocol handlers...

Looks like it is some half completed demo integration rather than production ready...

Send the link to yourself in whatsapp and then click on it.

Open a chat with yourself in whatsapp. https://wa.me/your-number . You can spam anything here, it's personal and only you can see it.

They send wa.me/number-of-person-you-are-contacting in that chat. Click on it and it will start a chat with person-you-are-contacting.

All numbers MUST be in international format. Country code and number.

I made a tool exactly to do this: https://trianguloy.github.io/OpenInWhatsapp_Web/

Yeah it used to be quite hopeless unless you opened the link in a tab that had already loaded WhatsApp web. Now however, if you click the green button that says "CONTINUE TO CHAT" on the initial screen, it'll load a page with an option to download WhatsApp and another that's titled "use WhatsApp Web", just click on that one. Unfortunately, it will load a new instance of WhatsApp web in the current window even if you already have another open in another tab.

Doesnt seems to work for me. Get directed to a page saying I don't have WhatsApp installed (I do).

Android v8, Firefox v68.6.

That is because you are opening in browser. You have to set wa.me links to open in app.

Open firefox settings, toggle 'open links in app'.

(or)

Open a chat with yourself in whatsapp. https://wa.me/your-number . You can spam anything here, it's personal and only you can see it.

They send wa.me/number-of-person-you-are-contacting in that chat. Click on it and it will start a chat with person-you-are-contacting.

All numbers MUST be in international format. Country code and number.

Reminds me of https://xkcd.com/1172/

They don't as much share info as live off the same ecosystem in your phone. Regular users, who don't actively block their FB apps from accessing their phones in depth, will store Whatsapp contacts on their phones, which in turn are read by the FB and/or Messenger app. Since neither knows the context, it just assumes its a new contact and show you info accordingly.

>I don't install the Facebook app and don't give Messenger Lite access to my contacts

Literally doesn't matter what you do, it's what other people do with your data. I can tell from this guy I interned for 15 years ago that at one point he uploaded his entire address book to Facebook including my name, email and phone number because he still shows up in facebook recommendations to me today on Facebook and IG.

Never gave them access to my contacts either or even had him in my contacts but FB's shadow profile knows he knows who I am.

But your contacts do install the apps and Facebook can now match you.

I don't use their apps.

They are almost certainly sharing data behind the scenes, they openly say this in op's link about how WhatsApp uses your data:

> improving their services and your experiences using them, such as making suggestions for you (for example, of friends or group connections, or of interesting content), (...) across the Facebook Company Products;

There is a small chance that they've gotten all my data from the people at the other side of the conversation if they have the fb app installed I guess, which really isn't much better.

> Also, I find it annoying that you can't message someone on WhatsApp without adding them to contacts.

The trick that i use is to type their number into the domain wa.me in the following format https://wa.me/xxxxxxxxxxx

That allows you to open a chat to that specific number without adding them to your contact list.

That’s a neat trick, but “Works for me” is not a solution for mass surveillance.

> Also, I find it annoying that you can't message someone on WhatsApp without adding them to contacts.

You can, if you're both part of a group chat together. Tap on their number and a pop up comes up allowing you to message said person.

Also agree with the opinions expressed even with similar experience to yourself (no Facebook or messenger apps installed, WhatsApp contacts don't appear as suggestions on FB website).

There are also third party apps like "Click to Chat" that let you start conversations with phone numbers. Once you sent 1 message you can just use whatsapp normally.

> Also, I find it annoying that you can't message someone on WhatsApp without adding them to contacts.

Is this a new limitation? On iOS I'm still able to message someone new using only their phone number. Though I'm blocking contact access so perhaps that's why.