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First, I am not sure where to ask this. Please point me the correct stack exchange if it does not belong here.

Note: I do not know how to correctly name "mobile data" in english. But I refer to 3G/4G/etc.

To send or receive a MMS (Multimedia Messaging Service), I need to activate mobile data on my phone, even if I am connected to a network via Wifi.

Why is it required ? Why can't we use MMS via Wifi ? Depending on the type of subscription you have, it would be less expensive to use Wifi than mobile data, at least for the customer.

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  • It is unclear what you are asking. MMS is a protocol for sending messages over mobile data, so how would using it over WiFi even work? You would need to be within 30-100m of your intended recipient to even connect to them via WiFi. And the recipient may not even have WiFi. Commented Oct 21, 2020 at 6:49
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    @JörgWMittag I think "wifi" here is meant as connected to the internet throught "wifi" by opposition to being connected to internet through "mobile data"
    – JayZ
    Commented Oct 21, 2020 at 7:23
  • MMS is old tech, but today both iphone and android in some cases transparently skip the whole SMS/MMS tech when messaging compatible devices/contacts Commented Oct 22, 2020 at 7:12
  • Go to Settings Messages and turn on iMessages. MMS will then work without mobile data.
    – Davo
    Commented Aug 7, 2021 at 7:48

3 Answers 3

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MMS was conceived as a way of adding multimedia capabilities to SMS, not as an internet messaging platform. It uses a set of technologies which made sense in the mobile ecosystem of the time, but are definitely not how you'd design it today

In particular, it is built entirely on top of WAP, an internet connection protocol that has otherwise been completely superseded. Every part of the process is standardised around handsets connecting directly to their carrier's servers over WAP, not via any other internet connection.

While it would be possible to build an "MMS over TCP/IP" protocol, there would be little motivation to do so: the expense for the carriers is maintaining the complicated services which store, forward, and re-encode the messages, and the original protocol would still need to be supported for older handsets.

There have been attempts to replace both SMS and MMS with a more modern protocol, notably RCS, but it is hard to compete with services like WhatsApp which don't need the investment from carriers to implement.

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For the same reason you cannot send SMS over Wifi, it's a protocol for sending "Multimedia Messages" over the cellular phone networks (https://en.wikipedia.org/wiki/Multimedia_Messaging_Service). When MMS was first conceived publicly available Wi-fi was less common than cellular phone connectivity, so it was a way to send those messages without needing internet access.

Sometimes this distinction has been blurred by carriers and device providers, who provided hybrid solutions where sending an MMS to a number would forward it to an email or vice versea

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    "When MMS was first conceived publicly available Wi-fi was less common than cellular phone connectivity" – And even more importantly: phones simply didn't have WiFi. Commented Oct 21, 2020 at 9:55
  • your answer is proper, but SMS over Wifi really is possible ("SMS over IMS"), see 3gpp links at stackoverflow.com/a/72749032/7010943
    – wbob
    Commented Mar 17, 2023 at 11:54
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Why is it required ? Why can't we use MMS via Wifi ? Depending on the type of subscription you have, it would be less expensive to use Wifi than mobile data, at least for the customer.

Ultimately, these services are provided to make money for the mobile phone carriers.

If you want to send MMS messages over the phone network, then you have to buy a data plan from your phone provider. It is of no benefit to the provider to allow you to send MMS messages via WiFi when you are near a hotspot.

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