Chert - iMessage API for Business Messaging at Scale

TL;DR

TL;DR: Chert is a YC-backed API that gives businesses a programmable interface to send, receive, and automate iMessage conversations at scale — bridging the gap between iMessage’s human-friendly UX and the infrastructure needs of high-volume customer communication.

Source and Accuracy Notes

• Product: https://www.trychert.com
• Launch HN: Chert (YC P26) – Twilio for iMessage
• Demo: YouTube walkthrough

What Is Chert?

iMessage is everywhere in the US — the blue bubble has typing indicators, reactions, and a polished UX that SMS cannot match. But unlike SMS, iMessage has no native API. Businesses that want to automate iMessage conversations at scale have historically had to build fragile, custom infrastructure or go without.

Chert solves this by providing a clean REST API wrapper around iMessage infrastructure. Think of it as Twilio for iMessage — businesses get a programmable interface to send and receive iMessages without managing the underlying complexity of Mac-based relay infrastructure, phone line health, or SMS fallback routing.

The team came from building AI agents on top of iMessage and discovered that the highest-demand use cases were not B2C agents at all. Instead, they were high-volume business communications: customer service, missed-call text-back, cart abandonment recovery, and inbound lead capture for home services, DTC brands, and property management.

API Design and Core Endpoints

Chert exposes a REST API that integrates with existing systems. The key capabilities:

Sending and Receiving

Businesses POST messages through the API and Chert routes them through its iMessage infrastructure. Inbound replies flow back via webhook — you receive a POST to your endpoint with the message content and sender details.

SMS/RCS Fallback

When iMessage delivery fails (recipient has iMessage disabled, or the line is unhealthy), Chert automatically falls back to SMS or RCS. This is critical for business use cases where a missed message means a lost customer.

Line Health Monitoring

Chert performs ongoing health checks on registered phone lines and alerts you when a line degrades — preventing silent message failures before they affect customers.

Deeper Analysis

Why iMessage First?

The team spent time building AI agents on iMessage because the platform has distinct UX advantages over SMS: typing indicators signal engagement, reactions let recipients respond minimally without a full reply, and the overall polish reduces the “bot feel” that plagues SMS-based interactions.

But scaling iMessage automation revealed that B2C AI agents were not the primary market. High-volume business communications — especially in verticals with high inbound inquiry rates — drive the real demand. A property management company answering lease inquiries, a home services firm handling appointment requests, a DTC brand managing cart abandonment — these use cases need reliable, scalable iMessage infrastructure, not a custom-built Mac relay setup.

The Infrastructure Problem Chert Solves

Setting up iMessage automation yourself typically means:

• A Mac machine running 24/7 with a registered phone number
• AppleScript or native client libraries to send messages
• Handling rate limits, device reboots, and network interruptions
• SMS fallback logic when iMessage fails
• Scaling to multiple phone numbers for volume

Chert abstracts all of this. You call an API endpoint; Chert handles the relay infrastructure, health monitoring, and fallback routing.

Practical Evaluation Checklist

• Sign up at trychert.com and get API credentials
• Send a test message via the API dashboard or curl
• Configure a webhook endpoint to receive inbound messages
• Review the SMS fallback behavior when iMessage is unavailable
• Check the line health dashboard for registered numbers
• Integrate with an existing CRM or automation tool using the REST API

Security Notes

Chert handles message content and phone numbers — treat the API key with the same sensitivity you would any messaging platform credentials. Ensure your webhook endpoint validates incoming requests to prevent spoofing. Business use cases involving PII or customer data should be reviewed against your compliance requirements before production deployment.

FAQ

Q: How does Chert send iMessages — does it use a physical Mac?

A: Chert handles all infrastructure internally. The underlying relay uses Mac-based nodes running registered phone numbers, but the operational complexity (health monitoring, failover, scaling) is abstracted away. You interact only with the REST API.

Q: What happens if iMessage delivery fails?

A: Chert automatically falls back to SMS or RCS when iMessage is unavailable. The fallback routing is built into the platform, so you do not need to implement separate logic for this.

Q: Is there a free tier for testing?

A: Check the pricing page at trychert.com for current tiers. The launch HN post mentions a demo and walkthrough video for evaluating the platform.

Q: What phone numbers does Chert support?

A: The platform works with standard US phone numbers capable of iMessage. Registration and number management are handled through the Chert dashboard.

Q: Can I use Chert for high-volume outbound campaigns?

A: Yes — the platform is specifically designed for high-volume use cases like customer service, cart abandonment, and missed-call text-back. Volume limits and rate controls apply based on your tier.

Conclusion

Chert fills a real gap in the business messaging stack. SMS has Twilio; iMessage did not — until now. For businesses that rely on iMessage’s engagement rates and UX advantages, Chert provides the API infrastructure to automate and scale those conversations without building custom relay infrastructure.

The combination of iMessage’s human-friendly UX, automatic SMS fallback, and built-in line health monitoring makes it a practical option for high-volume customer communication in text-heavy verticals. If your business depends on iMessage outreach, this is the API layer that makes it production-ready.

Explore the demo and API at trychert.com.