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AS4
Post-AS2 Landscape: Preparing for AS4 and Beyond
Discover why AS4 is the future of secure B2B communication, how it compares to AS2, and how to prepare for evolving EDI standards.
Thanura Jayatissa
Published: 18 Jul 2025
In the world of B2B communication standards, AS2 has long been the dominant protocol for secure and reliable document exchange. It’s the protocol behind countless EDI (Electronic Data Interchange) workflows, powering supply chains across industries like retail, healthcare, logistics, and manufacturing. But as technology evolves and the demand for more dynamic, flexible integration grows, the conversation is shifting towards AS4.
So what is AS4, and why is it gaining traction now? Will AS2 disappear completely? More importantly, how should organizations prepare for this next phase in the evolution of secure data exchange?
Let’s look into what the future may look like beyond AS2.
AS2: Still a Pillar of B2B Communication
Before diving into AS4, it’s worth recognizing why AS2 became so widely adopted in the first place. Introduced over two decades ago, AS2 (Applicability Statement 2) allowed businesses to securely exchange EDI documents over the internet using HTTPS and digital certificates.
What made AS2 revolutionary at the time was its ability to replace costly VAN (Value Added Network) connections with internet-based communication, without compromising security. It enabled encryption, digital signatures, and MDNs (Message Disposition Notifications), which gave businesses the confidence that their sensitive transactions like purchase orders, invoices, shipping notices etc reached the intended recipients.
Even today, companies like Walmart, Amazon, and the U.S. FDA use AS2 extensively. It works well and is supported by a mature ecosystem.
The Rise of AS4: A Modern Approach to EDI
AS4 (Applicability Statement 4) builds on the foundation laid by AS2, offering a more robust and future-ready solution. Based on web services protocols (SOAP) and developed by OASIS, AS4 addressed some of the gaps left by AS2 by aligning with more modern enterprise integration strategies and regulatory frameworks.
Here are some standout advantages of AS4:
-
Improved interoperability
AS4 uses standard web services (SOAP, XML), making it easier to integrate with APIs, cloud platforms, and service-oriented architectures (SOA). -
Advanced security
While AS2 relies on S/MIME and HTTPS, AS4 incorporates WS-Security, a more flexible and extensible model for authentication, encryption, and integrity checks. -
Message pulling support
Unlike AS2, which is mostly push-based, AS4 allows message pulling. This is valuable in scenarios where inbound firewall restrictions make it hard to receive incoming HTTP posts. -
Built-in reliability
AS4 supports WS-ReliableMessaging, offering better delivery guarantees, retries, and sequencing.
These features make AS4 especially attractive to industries with complex integration needs, such as finance, government, and multinational trade.
AS2 vs. AS4: Side-by-Side
| Feature | AS2 | AS4 |
|---|---|---|
| Protocol Base | HTTP/HTTPS + MIME | SOAP (Web Services) |
| Reliability | Basic (optional MDN) | Built in with WS-reliable messaging |
| Security | S/MIME, SSL/TLS | WS-Security (flexible, token-based) |
| Interoperability | Good | Strong (due to service-based standards) |
| Deployment Complexity | Lower | Higher (web service stack required) |
AS4 is designed to complement AS2, rather than replace it, especially in environments where the advantages of web services architecture can be fully exploited.
👉 Choosing the Right Protocol for Your Business Needs
Is AS2 Going Away? Not So Fast.
While AS4 is promising, AS2 is not going away anytime soon.
A lot of worldwide corporations have a significant investment in using their AS2 systems. Upgrading isn’t as easy as flipping a switch, it involves partner coordination, system upgrades and retesting. What’s more, since the AS2 still meets the regulatory and operational requirements of many industries, there is no urgent requirement to ditch it.
How to Prepare for AS4 (and Beyond)
If your organization currently uses AS2, now is a good time to start laying the groundwork for AS4 readiness, even if you’re not planning to switch in the next 2 years.
Here’s how to start:
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Evaluate your current EDI setup – Understand your current tools, partners, and protocols. Is AS4 supported by your MFT or EDI solution? Can it handle SOAP-based communication?
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Talk to your trading partners – Ask key trading partners about their AS4 plans. If they’re starting to embrace AS4 then you may need to revise your project timelines.
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Choose flexible technology – Consider investing in integration technology that can handle both AS2 and AS4. This two-prong support may help you while managing a hybrid environment in that transition time.
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Stay on top of compliance – Regulations are evolving. A few government agencies might end up making AS4 mandatory, for international or for public sector exchanges especially.
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Start with small pilot projects – Start with a few AS4-enabled trading partners. Learn from those early integrations before scaling across your network.
Conclusion
AS2 has had a successful run, providing secure and reliable B2B communications over the past two decades, and still is a tried and true standard. Many organizations, including our own MFT Gateway customers, continue to rely on AS2 every day to power critical supply chain and integration workflows.
With that said, the rise of AS4 is already defining how data exchange will happen in the future, and particularly relevant to businesses who need their data exchange to be compliant with modern APIs and regulatory change or to be run across borders.
But it doesn’t need to be a disruptive shift. In fact, it’s an opportunity. So as long as you know where the industry is going and slowly get your systems in place, you can build a future-proof integration strategy that works today and in the future.
Through our MFT Gateway platform, we at Aayu Technologies continue to support strong AS2 integrations while also keeping an eye on the future with standards like AS4, so your business stays both secure and future-ready.
Thanura is a Senior Software Engineer at Aayu Technologies with nearly 1.5 years of experience mastering various products at Aayu. During this time, he has gained extensive knowledge of Aayu's diverse product line, particularly in B2B communications and cloud technologies. Away from the screen, he enjoys the thrill of watching cricket matches and cherishes moments spent with friends.
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