What is RCS, and why are some messages green and some blue?
The messaging standard that finally replaced plain texts between iPhone and Android, what it changes about privacy and picture quality, and what the colours in your messages app actually indicate.
- Difficulty
- beginner
- Time
- 20 min
- Read
- 6 min
Short answer
RCS is the modern replacement for SMS: it works over the internet rather than the mobile network, so it gives you typing indicators, read receipts, full-quality pictures, and — on current software with a supporting network on both ends — end-to-end encryption between iPhone and Android. Blue on an iPhone still means iMessage between Apple devices. Green now covers both plain SMS and RCS, which is why the colour alone no longer tells you much.
For over a decade, messages between an iPhone and an Android phone fell back to SMS: 160 characters, pictures compressed to the point of uselessness, no read receipts, and no encryption of any kind. RCS was the mobile industry's answer, adopted by Google years before Apple, and the standoff made the colour of a message bubble into a genuine social marker. That has now changed. Apple added RCS support, and in 2026 end-to-end encryption arrived for RCS between the two platforms, built on the industry's Universal Profile 3.0 specification. The practical result is that a cross-platform conversation can now be private and full quality, which was not true before — and that the colour of a bubble is a much weaker signal than it used to be.
Step by step
- Understand what RCS replaces.SMS and its picture-message cousin, both designed in the era of the mobile network's own signalling channels. They are limited in length, heavily compress pictures, have no encryption at all, and are billed by the network. RCS carries the same conversations over the internet instead, with none of those limits.
- Know what you actually gain.Full-resolution photos and video, longer messages, typing indicators, read receipts, better group chats, and the ability to send over wifi with no mobile signal. For many people the picture quality is the visible difference — cross-platform photos stopped looking like they were sent in 2005.
- Understand the encryption position, because it changed recently.RCS between Android users has been end-to-end encrypted in Google Messages for some years. Encryption between iPhone and Android arrived in 2026, based on the GSMA's Universal Profile 3.0, and rolled out through iOS and Google Messages updates with network support required at both ends. Encrypted conversations show a lock icon; without it, the message is not end-to-end encrypted.
- Read the colours correctly on an iPhone.Blue is iMessage, between Apple devices, encrypted. Green is everything else, which now means either RCS or plain SMS. The send field text tells you which — it says iMessage, RCS, or Text Message. That label is more informative than the colour.
- Check whether RCS is actually on.On Android it is in the Google Messages settings under RCS chats, and it verifies your number with the network. On iPhone it is in Settings, Apps, Messages, and it needs your network to support it. Both need it on at both ends of a conversation to be used.
- Know what makes a conversation fall back.No internet at one end, RCS switched off, a network that does not support it, an older phone, or a group with a participant who cannot use it. The messages app falls back silently, so a conversation can move between systems without any announcement.
- Decide whether it changes what messaging app you use.RCS narrows the gap with WhatsApp and Signal considerably for one-to-one chats. It is still tied to phone numbers, still dependent on network support, and still falls back to unencrypted SMS invisibly — so for conversations where privacy genuinely matters, a dedicated encrypted app remains the more predictable choice.
- Understand the billing.RCS uses data rather than your text allowance. On an unlimited-data plan that is free; on a small data allowance a lot of video sent over RCS will consume it. Abroad it uses roaming data unless you are on wifi, where SMS would have used your texts allowance instead.
Common mistakes
- Assuming green means insecure and blue means secure — That was broadly true until recently and is now wrong. A green RCS conversation with a lock icon is end-to-end encrypted; a green SMS conversation is not encrypted at all. The lock, not the colour, is the indicator.
- Treating RCS as equivalent to WhatsApp or Signal for sensitive conversations — It falls back to plain SMS silently when conditions are not met, and the fallback is not encrypted. A dedicated encrypted app either works or fails visibly, which is the property you want when it matters.
- Turning RCS off to save data without checking your allowance — Ordinary text conversations use a trivial amount of data. It is only heavy video and picture sending that adds up, and even then usually less than a single video stream.
If it doesn't work
Messages to one person are green, to another blue
Cause: That person is on Android or has iMessage off — Fix: Nothing is wrong. Green means the conversation is using RCS or SMS rather than iMessage, which is expected for anyone not on an Apple device.
RCS will not turn on or stays "Setting up"
Cause: Network verification has not completed — Fix: It verifies by sending a message to your own number and needs mobile signal, not just wifi. It can take some time, and a small number of networks and virtual operators do not support it at all.
Photos still arrive tiny and blurry
Cause: The conversation fell back to picture messaging — Fix: Check the send field label. If it says Text Message rather than RCS, the message went by the old system, which compresses heavily. That is the visible cost of a fallback.
No lock icon on an RCS conversation
Cause: Encryption is not active for that conversation — Fix: Both ends need current software and supporting networks. The rollout is staged, so absence of the lock means it is not encrypted rather than that something is broken.
RCS stopped working after changing SIM or network
Cause: Registration is tied to the number and network — Fix: Turn RCS off and back on to re-verify. It has to re-register after a SIM change, and it does not always do so on its own.
Group chat lost features when one person joined
Cause: The group fell back to the lowest common system — Fix: A mixed group with one participant who cannot use RCS drops the whole group to multimedia messaging. This is the main remaining reason households move to a dedicated messaging app.
Questions people ask
Do I have to pay for RCS?
No. It is not a service you buy — it uses your data allowance instead of your texts allowance, and on wifi it costs nothing at all. Networks do not charge separately for it.
Does RCS work without a mobile network?
Once registered, it sends over wifi. Registration itself needs mobile signal, because it verifies your number, so a phone that has never registered cannot set it up on wifi alone.
Is iMessage going away?
No. iMessage continues to work between Apple devices with its own features, and blue bubbles are unchanged. RCS is what happens instead of SMS for everyone else, so Apple users now have three systems rather than two.
Can the network read my RCS messages?
Where end-to-end encryption is active, indicated by the lock icon, no — only the participants can. Where it is not active, RCS is encrypted in transit but the service provider can access the content, in the same way as most non-encrypted messaging. Plain SMS has no encryption at all.