iMessage API for business: how to send blue texts from your app

Apple has no public API that lets a business start an iMessage conversation, so any iMessage API for business that texts first runs on a "blue line": a line that sends as iMessage to iPhones and falls back to SMS for everyone else. With Ready's blue line you can send blue texts from your app through a REST API, for $99 a month per line plus $0.06/segment, with a cap of 50 new conversations per line per day.

This guide is for CTOs and product leads deciding whether their platform's texts should land blue. It covers what an iMessage API can and can't do, how a blue line behaves, what it costs next to SMS with worked math, and the cases where plain SMS is still the better channel. We make Ready, so we'll be specific about our own product, including where it isn't the right fit.

What Apple offers, and what it doesn't

When a product team says "we want iMessage," they usually mean one thing: an iPhone user gets a text from the business and it shows up as a blue bubble with the business's name and photo instead of a green bubble from an unknown number.

Apple doesn't sell that directly. Its business product, Apple Messages for Business, is built for conversations the customer starts. The customer taps a chat button on a website, in Maps or in an app, and the business replies. It works well for inbound support. It cannot send an appointment reminder, a "your order shipped" notice or a follow-up to a lead who filled out a form yesterday, because the business can't send the first message.

That gap explains the confusion in this category. When you look at iMessage API vendors, ask one question first: can this line text someone first?

• Apple Messages for Business: customer starts every conversation. Good for inbound support chat.
• A blue line (what Ready offers): the business can text first, within daily limits, and the message shows up as iMessage on iPhones.
• Plain SMS/MMS: the business texts first at whatever volume its 10DLC registration allows, and every phone shows a green bubble.

How a blue line works

A blue line is a line on your Ready account that sends as iMessage. From the recipient's side:

• iPhone users see a blue bubble with your business's name and photo.
• Android users get the text from the account's regular number. If the account has no regular number yet, a blue line comes with a green one, and once the account registers its texts bill at 6 cents a segment.
• Replies, reactions, typing indicators and group chats all land in the same inbox thread as your SMS conversations, so your support or sales team works from one inbox.

A blue line doesn't need 10DLC registration. A business can start texting as soon as the line is set up. With SMS, by contrast, most approvals take 2 to 7 days. For a platform onboarding customers who want to text this week, that difference matters.

The API reference is at docs.tryready.com/api/imessage, and the setup walkthrough is at docs.tryready.com/guides/imessage. We're not reproducing the blue line request shapes here. Use the docs so you're building against the current spec.

The limits that shape your product design

These caps decide which of your features can use the blue line, so read them before you scope anything.

1. Unlimited texting with people you already talk to. Once a conversation exists, there's no daily cap on that thread.
2. 50 new conversations per line per day. This is the number that matters most for capacity planning.
3. Up to 2 texts to a new person until they reply. You can't send a third nudge into silence.
4. Photos only after they reply. Your first message has to be text only.
5. Campaigns and drip campaigns send from regular numbers, not the blue line. A blue line is for conversations, not for broadcast.

If you need more than 50 new people a day, you add lines. The "Add lines automatically" setting can add a line when the day's new-conversation allowance runs out, so a spike in signups doesn't strand contacts.

Capacity math

Here's an example with stated assumptions. Your platform needs to open about 400 new conversations a day at peak.

• 400 ÷ 50 = 8 lines
• 8 × $99 = $792/month in line fees, before any per-segment charges

Compare that with SMS. A fresh 10DLC brand on T-Mobile at the lowest trust score gets roughly 2,000 messages a day, and higher trust tiers go up to roughly 200,000. For raw reach to new contacts, SMS scales much further per dollar. The blue line is a premium channel for conversations where the blue bubble earns its cost.

What it costs, blue line vs SMS

Here are the two channels side by side on Ready:

A note on the SMS column: the $0.0075/segment plus $0.0045 all-in figure excludes the compliance surcharge. Scrubbing and landline validation each add $0.003/segment when switched on for an account. Both are off by default.

Worked example: one customer's month

This is an example with assumptions you should replace with your own numbers:

• One line, about 40 new conversations a day, inside the 50 cap
• 6,000 segments a month, sent and received combined
• 60% of recipients on iPhone. That share is an assumption for the math. Check your own users' device mix.

Blue line plus green fallback:

• Line fee: $99
• iPhone traffic: 3,600 segments × $0.06 = $216
• Android traffic on the regular number: 2,400 × $0.0075 = $18, plus 2,400 × $0.0045
• The green side passes 500 texts a month, so the regular number needs 10DLC: $25/mo for registration and $2/mo per number
• Total: $365, plus 2,400 × $0.0045

That assumes the account already had a number. If the blue line came with its green number, the Android side bills at 6 cents a segment once the account registers: 2,400 × $0.06 = $144 instead of $48.

All SMS:

• 6,000 × $0.0075 = $45, plus 6,000 × $0.0045
• Registration: $27
• Total: $72, plus 6,000 × $0.0045

The blue line setup costs a little under $293 a month more once you net out the extra carrier fees on the SMS side. Whether that premium is worth it depends on what a reply is worth to that customer. Teams turn on the blue line because a named blue bubble looks like a conversation rather than a notification. We don't publish a measured reply-rate lift, so test it against your own SMS baseline before you price it into a plan.

For the wider cost picture across providers, see our SMS marketing pricing buyer's guide.

Where the blue line fits in a platform

Platforms that text on behalf of their customers can sort use cases by one question: is this a conversation, or a broadcast?

Good fits for a blue line:

• Speed-to-lead follow-up. A form fill triggers a text, and the lead replies in a thread that looks like a person wrote it. The 2-texts-before-reply rule fits naturally: one intro and one follow-up.
• Account manager or concierge threads. These are ongoing conversations with existing customers, which have no daily cap once the thread exists.
• High-value onboarding. A setup check-in to a new paying customer, where the person on the other end matters more than the cost per segment. Our post on onboarding SMS vs email covers the timing.
• Support follow-ups where the customer is likely to send back a screenshot. Photos are allowed once they've replied.

Poor fits:

• Anything you'd call a campaign or a drip campaign. These send from regular numbers by design.
• High-volume transactional traffic to people who haven't replied before, such as OTPs, shipping notices and appointment reminders at scale. The 50-new-per-day cap and the 2-text limit work against you here.
• Price-sensitive customers whose margins can't absorb $0.06/segment.

When SMS is still the right channel

SMS remains the right default for a lot of platform traffic.

• Volume to new contacts. If your platform's customers text thousands of new people a day, registered SMS is built for that. A blue line would need dozens of lines.
• Campaigns and drip campaigns. These run on regular numbers on Ready.
• 2FA and alerts. Keep these on SMS, and keep them on a separate number from marketing traffic. Our post on separating MFA and marketing numbers explains why mixing them gets both filtered.
• Lowest per-segment cost. If all you need is green SMS at the lowest unit price, a raw CPaaS such as Twilio at about $0.0083/segment costs less per segment than our Standard rate. What Ready adds on the SMS side is the platform layer: sub-accounts with their own 10DLC registration, TCPA and DNC scrubbing, number validation, opt-out handling and webhooks.

A plain SMS send through the Ready API looks like this. It's the same call your Android fallback traffic depends on:

POST https://api.tryready.com/v1/messages
X-API-Key: <your key>
Idempotency-Key: 3f6c1e2a-8b4d-4c11-9e7a-2d5b8f0a1c33
Content-Type: application/json

{"to": "+12125550199", "body": "Your order #1042 has shipped.", "consent_attested": true}

Send the Idempotency-Key on every request so a retry never sends twice. The full reference is at docs.tryready.com/api/messages, and our SMS API integration walk-through covers retries and webhooks.

Consent doesn't change with the bubble color

A blue bubble is still a text message to someone's phone. Treat consent for a blue line exactly as you treat it for SMS: only text people who agreed to hear from the business, or who reached out first. Your platform should store the opt-in record itself, meaning when the person agreed, the wording they saw and the page they agreed on, because the sender's attestation on a send is not a per-contact consent record. Compliance is ultimately the sender's responsibility. Ready's tooling reduces risk; it doesn't remove it.

The practical takeaway

There's no official Apple API for a business to text first. A blue line fills that gap, within limits you design around: 50 new conversations per line per day, 2 texts before a reply, photos after a reply, and no campaigns or drip campaigns. At $99 a line plus $0.06/segment, it's a premium channel for conversations. SMS stays the workhorse for volume, alerts and broadcasts.

To test it, pick one conversational flow in your product, such as lead follow-up or onboarding check-ins. Run it on a blue line for a month and compare replies and cost against the same flow on SMS. Start with the blue line guide, check current rates at tryready.com/pricing, and create an account when you're ready to build. A card on file is required to send, and the first 20 one-to-one texts are free.

FAQ

Is there an official iMessage API for businesses?

Not for business-initiated messages. Apple Messages for Business only supports conversations the customer starts. To text first and appear as iMessage, you need a blue line service like Ready's.

How much does it cost to send iMessage from an app?

On Ready, a blue line is $99 a month per line plus $0.06/segment for each text sent. Replies are also $0.06/segment, and reactions are free. Texts to Android phones go from your regular number. If you already had a number they bill at the regular text price; if the blue line came with its green number, your account's texts bill at 6 cents a segment once you register.

How many people can a blue line text per day?

Each blue line can start up to 50 new conversations a day. Texting with people you already talk to is unlimited. For more new contacts, add lines, or turn on "Add lines automatically."

Do I need 10DLC registration to send iMessage?

No, a blue line needs no 10DLC registration, so you can start texting as soon as it's set up. The regular number that handles Android recipients follows normal SMS rules. That means registration once it passes 500 texts a month, and most approvals take 2 to 7 days.

Can I send marketing campaigns over iMessage?

No, not on Ready. Campaigns and drip campaigns send from regular numbers over SMS. The blue line is built for one-to-one conversations, with up to 2 texts to a new person before they reply.