(messenger app v7.6.0 on android v8)
It took me quite some efforts, time and stress to understand following points, I'd like to share with others.
- When I first create a Telegram account, Telegram is asking if my phone contacts can be read. If I accept (which everybody very likely will do, not aware of the consequences), Telegram will upload all my phone contacts on their (cloud) servers. In this process, Telegram will check 2 things: 1) is any on these contacts already member of their club (= already created a Telegram account before) AND 2) is any of these contacts having my phone number (the number I used for the Telegram account creation!). When I say "is having" it means that they have my phone number (known by Telegram) in the contacts which were synchronised (uploaded) with the Telegram servers, on their side. If both checks can be answered by yes, all these people will immediately be informed by a notification and chat creation, that I just joined Telegram! (The notification can be switched off in the app settings but the chat creation simply CANNOT!).
- If I don't change my privacy settings, any further contact I'll save in my phone contacts will be immediately uploaded (=synced) on the Telegram (cloud) servers and the process of automatic information (see above) will be continued.
- I can only see in my Telegram contacts, people who created an account on Telegram, connected with a phone number which is saved my phone contacts (and this number has been synchronised with the Telegram servers). Hence if one of my phone contacts created a Telegram account with another number than the number I have saved in my phone contacts, I won't be able to see this contact in my Telegram contacts. So concretely it means that, if I created a Telegram account with number B, and the person I'm having in my phone contacts (having my number A in its phone contacts) also created a Telegram account, I will see this contact in my Telegram contacts BUT the person will NOT see me in his Telegram contacts at all!
- The "last seen" status always remains visible (although only in terms of recently (1-3 days), week, month, long time ago), whatever setting you choose in the privacy settings. Only blocked contacts will always just see the "last seen a long time ago" status.
- If you set your profile photo (in privacy settings) to be visible only for "My Contacts", it concretely means that the contact must be somehow mutual. So what does mutual mean? For sure it means "if both are seeing each other" in their respective Telegram contacts list. Now there is probably also an additional scenario possible: I didn't test this but I assume, if there is a chat (even empty, as when it's automatically created), it's very likely considered as mutual too. To be concrete, if created my Telegram account with phone number B and my "friend" is having my phone number A (or none at all) saved in his phone contacts (while syncing with Telegram), I can see his pic by default. Now if he is later changing his privacy settings to 'My Contacts' only, I guess it will remain like that. To be very clear, I didn't test this so far, so it's just an assumption. (Feel free to correct me if my assumption is wrong.) Last but not least, there is a way to add exceptions in the privacy settings, but all this is not active by default.
Bottom line: I don't like (not to say I hate) the way Telegram is handling privacy. You need almost to be a rocket scientist, to understand all what is going on in the background (on their cloud servers and in their main offices in Dubai, United Arab Emirates). There's simply no transparency at all and no precise information given, especially prior becoming member of their fan club. You can (and your really should!!) got through all the possible settings hidden under "privacy and security". But even then, for most of us it will have been too late anyway!
You can of course (as I did) switch off the (future!) contact synchronisation. That being said, you have to weigh the pros and cons for yourself, about also deleting all the already automatically uploaded contacts. Be aware that "delete synced contacts" deletes all the Telegram contacts only, so your phone contacts (saved prior to install the app) will not be touched! If you just switch off the synchronisation, it will not change anything in the present moment, so understand well this important difference.
I hope this post was not too confusing and will help others. Feel free to comment or correct me, if something is wrong.
It took me quite some efforts, time and stress to understand following points, I'd like to share with others.
- When I first create a Telegram account, Telegram is asking if my phone contacts can be read. If I accept (which everybody very likely will do, not aware of the consequences), Telegram will upload all my phone contacts on their (cloud) servers. In this process, Telegram will check 2 things: 1) is any on these contacts already member of their club (= already created a Telegram account before) AND 2) is any of these contacts having my phone number (the number I used for the Telegram account creation!). When I say "is having" it means that they have my phone number (known by Telegram) in the contacts which were synchronised (uploaded) with the Telegram servers, on their side. If both checks can be answered by yes, all these people will immediately be informed by a notification and chat creation, that I just joined Telegram! (The notification can be switched off in the app settings but the chat creation simply CANNOT!).
- If I don't change my privacy settings, any further contact I'll save in my phone contacts will be immediately uploaded (=synced) on the Telegram (cloud) servers and the process of automatic information (see above) will be continued.
- I can only see in my Telegram contacts, people who created an account on Telegram, connected with a phone number which is saved my phone contacts (and this number has been synchronised with the Telegram servers). Hence if one of my phone contacts created a Telegram account with another number than the number I have saved in my phone contacts, I won't be able to see this contact in my Telegram contacts. So concretely it means that, if I created a Telegram account with number B, and the person I'm having in my phone contacts (having my number A in its phone contacts) also created a Telegram account, I will see this contact in my Telegram contacts BUT the person will NOT see me in his Telegram contacts at all!
- The "last seen" status always remains visible (although only in terms of recently (1-3 days), week, month, long time ago), whatever setting you choose in the privacy settings. Only blocked contacts will always just see the "last seen a long time ago" status.
- If you set your profile photo (in privacy settings) to be visible only for "My Contacts", it concretely means that the contact must be somehow mutual. So what does mutual mean? For sure it means "if both are seeing each other" in their respective Telegram contacts list. Now there is probably also an additional scenario possible: I didn't test this but I assume, if there is a chat (even empty, as when it's automatically created), it's very likely considered as mutual too. To be concrete, if created my Telegram account with phone number B and my "friend" is having my phone number A (or none at all) saved in his phone contacts (while syncing with Telegram), I can see his pic by default. Now if he is later changing his privacy settings to 'My Contacts' only, I guess it will remain like that. To be very clear, I didn't test this so far, so it's just an assumption. (Feel free to correct me if my assumption is wrong.) Last but not least, there is a way to add exceptions in the privacy settings, but all this is not active by default.
Bottom line: I don't like (not to say I hate) the way Telegram is handling privacy. You need almost to be a rocket scientist, to understand all what is going on in the background (on their cloud servers and in their main offices in Dubai, United Arab Emirates). There's simply no transparency at all and no precise information given, especially prior becoming member of their fan club. You can (and your really should!!) got through all the possible settings hidden under "privacy and security". But even then, for most of us it will have been too late anyway!
You can of course (as I did) switch off the (future!) contact synchronisation. That being said, you have to weigh the pros and cons for yourself, about also deleting all the already automatically uploaded contacts. Be aware that "delete synced contacts" deletes all the Telegram contacts only, so your phone contacts (saved prior to install the app) will not be touched! If you just switch off the synchronisation, it will not change anything in the present moment, so understand well this important difference.
I hope this post was not too confusing and will help others. Feel free to comment or correct me, if something is wrong.
