Versions and maturity

How stable is this part?

Before you build on any part of FHIR, ask how stable it is. Two labels tell you: its standards status, and its maturity level.

Normative, trial use, draft

The standards status says how settled something is. Normative content was approved by the ANSI process in a previous version, and is locked, so changes are infrequent and tightly constrained. Trial use content is well reviewed and ready to use, but future versions may change it in incompatible ways. And draft content is not complete enough to be safe to implement, and is use at your own risk. Informative and deprecated are two further labels: for guidance only, and for outdated content.

• Draft · Not safe to implement yet. · warning
• Trial use · Ready to use; may change. · gear
• Normative · Locked; change is rare. · lock

Maturity builds up

The maturity level, called FMM, shows how advanced an artifact is. Each level includes the one before. Level one: substantially complete, and ready for implementation. Level two: tested between at least three independently developed systems. Level three: a round of formal balloting, with implementer comments. Level four: published as a standard for trial use, and tried in multiple prototype projects. Level five: two publication cycles, and at least five independent production systems in more than one country. And the top level, normative, means locked down.

• FMM 1 · Substantially complete · check · navy
• FMM 2 · Tested across three systems · share · navy
• FMM 3 · A ballot round and comments · pencil · amber
• FMM 4 · Published; prototype projects · file · slate
• FMM 5 · Production use in many countries · globe · slate
• FMM 6 (N) · Normative: locked down · lock · slate

Maturity, read off a real page

Here is how it looks on a real page. Under the heading of the Patient page, the maturity level reads N, which means normative, the top level. And the standards status reads normative, from version four point zero point zero. So this content is locked, and it has been since release four.

• 1 · 0.234 · 0.745 · 0.115 · 0.215
• 2 · 0.352 · 0.745 · 0.165 · 0.215
• 1 · Maturity Level: N · N means normative, the top level.
• 2 · Normative (from v4.0.0) · Approved as normative in release 4.

A version has three numbers

A FHIR version is written major, minor, patch. The major number is a significant new release: release four is version four. The minor number marks minor substantive changes: release four B is version four point three point zero. And the patch number marks technical corrections only: four point zero point one is the first correction to four point zero point zero.

• Major · A significant new release · star
• Minor · Minor substantive changes · gear
• Patch · Technical corrections only · check

Releases you will meet

These are the releases you will meet. Release three is version three. Release four is version four, with normative and trial use content. Release four B is version four point three, with trial use changes only. And release five is version five. As of October 2026 the specification marks release five as the current published version. Always check which release a guide or system uses.

• R3 · Version 3 · An earlier STU release. · file
• R4 · Version 4 · Normative and STU content. · lock
• R4B · Version 4.3.0 · STU changes only. · pencil
• R5 · Version 5 · STU; current in October 2026. · star

Forward and backward compatibility

Once content is normative, compatibility rules apply. Forward compatibility means content that is conformant in an old release stays conformant in future releases. FHIR's rules try to enforce this for normative content. Backward compatibility means content from a newer release works with an older one. That is not guaranteed, though a system can improve its chances, for example by ignoring elements it does not expect.

Check yourself

Pause and think. What does a normative standards status tell you? The answer: the content is locked, and change is infrequent and tightly constrained.

• The content is locked, and change is infrequent and tightly constrained
• The content is a draft and unsafe to implement
• The content will change freely in the next release
• The content is only an example

Keep these in mind

Standards status is draft, trial use, or normative. Maturity builds up from one to normative. A version is major, minor and patch. And always check which release you are using.

• Status: draft, trial use or normative
• Maturity (FMM) builds from 1 up to normative
• A version is major, minor and patch
• Always check which release you are using