If you're building healthcare applications, you'll learn quickly that "the EHR market" isn't a single market. It's a fragmented landscape of vendors, each with their own technical approaches, market positions, and integration requirements.

Which EHR systems you support determines which patients you can reach, which health systems will work with you, and how much engineering effort you're signing up for. Here's what you need to know about the major players.

The Big Two: Epic and Cerner (Now Oracle Health)

Epic dominates the large health system market — deployed at most major academic medical centers, large integrated delivery networks, and prestigious health systems. They claim records for over 300 million patients in the US.

For developers, Epic offers a robust FHIR API platform through fhir.epic.com. Their developer program is mature, the sandbox is accessible, and documentation is extensive. The App Orchard (now Showroom) provides a marketplace for approved applications.

The catch: Epic deployments vary by customer. Each health system configures Epic differently, which affects available data and API behavior. Getting to production means clearing Epic's app review process first, then individual health system approvals on top of that.

Cerner — acquired by Oracle in 2022, now Oracle Health — is the other major enterprise player, with strong presence in large hospital systems, federal healthcare (VA, DoD), and significant international deployments.

Their FHIR APIs are available through the Cerner developer portal. The Oracle acquisition has brought changes to their developer program and roadmap, with increasing emphasis on Oracle Cloud infrastructure. That transition has also created some uncertainty about long-term direction that's worth tracking if you're planning a Cerner integration.

The Ambulatory Players

athenahealth focuses on ambulatory practices — physician offices, clinics, and outpatient settings. Their cloud-native architecture means more consistency across customers than you'd get with on-premise deployments, and their FHIR API program provides solid access. The important thing to understand about athena: it covers a fundamentally different market segment than Epic or Cerner. Adding athena expands your reach to ambulatory practices but doesn't help with hospital data.

eClinicalWorks is another major ambulatory EHR, particularly popular with primary care practices and community health centers — over 150,000 providers on their platform. Their developer program and API access have improved meaningfully in recent years, driven partly by information blocking regulations. Worth noting: eClinicalWorks faced significant regulatory scrutiny in the past, including a major DOJ settlement over certification practices. Their technical infrastructure has evolved considerably since then.

NextGen Healthcare serves ambulatory practices with particular strength in specialty care settings, and has expanded its API offerings to meet Cures Act requirements.

Specialty EHRs

Flatiron Health focuses specifically on oncology — used by cancer centers and oncology practices, with data models optimized for cancer care including treatment protocols and outcomes tracking. If your application serves oncology patients, Flatiron coverage matters.

Modernizing Medicine serves specialty practices across dermatology, ophthalmology, orthopedics, and others. Their EMA platform is built around specialty-specific workflows, and integrating with it expands coverage for applications serving those patient populations.

The Coverage Math

No single EHR covers the entire market. A patient might have Epic records from their hospital, athena records from their primary care doctor, and Modernizing Medicine records from their dermatologist — all separate systems, all requiring separate integrations to access.

How many you need depends on who you're building for:

• Hospital-centric applications: Epic and Cerner cover most large hospitals

• Primary care focus: Add athena and eClinicalWorks for ambulatory coverage

• Specialty care: Consider Flatiron, Modernizing Medicine, or other specialty-specific systems

• Comprehensive consumer applications: You need broad coverage across all segments

Each integration is its own project — different developer portals, different authentication implementations, different data mappings, different quirks.

The Consistency Problem

FHIR was supposed to standardize healthcare data exchange, and compared to the pre-FHIR era, it's a genuine improvement. But FHIR implementations aren't identical across vendors. Each EHR supports different resource types, uses different extensions for vendor-specific data, maps clinical concepts to FHIR fields differently, and implements search parameters inconsistently — with its own rate limits and performance characteristics on top of all that.

Building an application that works consistently across EHRs means building normalization logic, handling gracefully when data is missing, and testing across multiple platforms. That's integration engineering, not product development. It's necessary work, but it doesn't differentiate your product.

The Infrastructure Option

We've built integrations across Epic, Cerner, athena, eClinicalWorks, NextGen, Flatiron, and Modernizing Medicine. The vendor variations, the FHIR inconsistencies, the data normalization — we've worked through all of it.

Our API gives you access to patient-authorized data across these systems through a single integration point. No managing seven different EHR relationships. No handling FHIR variations yourself.

You could build this infrastructure directly — roughly 2-3 months per EHR, plus ongoing maintenance. Or you integrate with us and reach the same patient populations immediately.

The EHR landscape is fragmented. Your integration approach doesn't have to be.