Q for those who know about iPhones!

I've just sent 2 text messages, maybe 5 minutes apart, iPhone to iPhone.

I know for a fact that I haven't changed location/position, and I also know that the recipient is still in the exact same office location.

Pressed 'send' at the end of the first text, and initially it showed blue on my screen, which (on my understanding) means it was sent as an "iMessage".

30 seconds-ish later, I heard a tone, and noticed the message had now altered to green, endorsed with "sent as text message".

My 2nd message, between the exact same users/phones/locations, showed in blue...and has remained blue, endorsed "delivered".

If the phones/locations are exactly the same, why the difference?!

I've come across this before, but struggled to find an explanation!

It could be due to the recipient not having the mobile data switched on/phone not connected to a router.

It could be due to the recipient not having the mobile data switched on/phone not connected to a router.

No phone settings were altered in the circa 5 minute time difference, so think we can rule that one out....

iMessage uses data to send and receive. If the sender or the target did not have a mobile data connection at that time, it could be that the phone sent the message as a text instead.

Mobile data signals sometimes drop for a few seconds/minutes.

Mobile data signals sometimes drop for a few seconds/minutes.

That may well explain it, I guess.

It's not the first time it's happened by any means, but seems to occur most often with certain recipients...without checking, roughly 25% of my contacts list, perhaps.

It does tend to get a bit irritating - especially if I'm wanting an urgent reply to a query - as sometimes my indignant "need to know now!" follow-up text is received before the original! (That's actually what happened earlier, and hence my question!)

Thanks for your help!

This is not so much a question about iPhones, but how mobile phone technology works. when you send and receive data via the cellphone system, a busy network can hand off your data to a more distant cell tower. In this case you might only get a plain text message as it may be a slower connection that goes via a different route.

If both iPhones are connected to a good wi-fi signal then you would expect that it would go via the internet instead and I would expect that to be an iMessage on an iPhone.

No data is sent instantaneously and most of it is queued.

The actual process itself takes miliseconds, but if the wifi connection at either end drops out for as little as ten milliseconds and your iMessage is sent in the middle of that 10 miliseconds, the iMessage fails and the phone will send again as an SMS message over GPRS/3G/4G if that is available.