Simplifier is a repository for FHIR resources. There are a multitude of resources that are available to the public including profiles, extensions, valuesets, dictionaries, mappings, examples and more.

Resource page

You can visit the page of a resource by selecting the resource from your search results or the Resources tab in your project, or following the direct link to the resource. While viewing resources you can display information in a few different ways.

Depending on the type of resource, the different views include:

  • Overview – This is either a preview (e.g. texts) or a Logical view (e.g. profiles) of the resource. The Logical view of a profile includes Element names in the leftmost column followed by Flags, Cardinality, Type, and  Description & Constraints.
  • Details – This is an easy-to-read list per element of all the details of a profile. The specification refers to this as the dictionary.
  • Mappings - This is a list of all the mappings specified in a profile.
  • Table – This is a simple table view of the resource.
  • XML & JSON – Respective views of resources in either XML or JSON formatting.
  • History – On this tab you can view the difference between two versions of the same profile. This is a great feature for comparing and tracking changes.
  • Issues - On this tab users with a paid account can track issues. New issues can be created by clicking the New issue button. The issue list can be filtered on open, closed or your own issues. By clicking on an issue you can read the entire conversation and add a new comment.

Update Resources

When you want to update your resource, there are several ways to do so. Choose one of the following options from the Update menu at the top of the Resource page:

  • Upload: Update by uploading a file (either XML or JSON)
  • Fetch: Update by fetching from a different FHIR server (provide a GET request to the server where your resource is located)
  • Edit: Update by editing the last version (opens a XML-editor in a small window where you can directly edit the XML code of your resource)
  • Editor: Update by editing the last version (opens a stand-alone full screen XML-editor in a different tab where you can directly edit the XML code of your resource)

Download Resources

You may also choose to download the resource and save a local copy on your computer. You can either choose to download the resource as a XML or JSON file or directly copy the XML or JSON code of the resource to your clipboard, so you can easily copy-paste it to another location.

Add Resources

Go to your Project page to add new resources to your project.

Sharing resources with Snippet

The Snippet feature in Simplifier enables you to quickly share resources with another Simplifier user (e.g. for review purposes) without storing them in your project. Click on the Snippet button in the top right corner to use this feature.


Start by giving your Snippet a title, e.g. MyPatient. You can either upload a file or copy-paste your XML code in the editor. Select Add another file to upload more than one resource within the same Snippet. When you are finished uploading and editing your resources, click on the Create button on the right.

Your Snippet will now be available on Simplifier. The URL is displayed at the top right of the Snippet. You can quickly copy the URL to your clipboard by clicking on the Copy icon at the right.


When visiting the URL of a Snippet, you can choose to view either the XML code, JSON code or the rendered resource by selecting one of the available tabs. In the top right menu you can either select Edit to edit the resource, Clone to copy it in a new Snippet, New to create a new Snippet or Download to download the resource as a XML or JSON file. You can also validate the resource by using the green Validate button at the right.


Personal Snippets

Through your personal menu (click on your avatar at the top right and select Snippets) you can access a list of all your Snippets. From here you can also quickly add a new Snippet by clicking the green +New button.


Metadata Expressions

The metadata expressions editor enables you to define what Simplifier should display as Title and Description for your resources. To start editing the metadata expressions of your project, select Settings and click on Metadata Expressions.

In the default tab you can see the default expressions used by Simplifier. You can add your customized expressions in the editor window. If your FHIR PATH expressions are missing, are not correct or the value extracted is empty, Simplifier will fall back to the default expressions. If a default expression is not able to provide a value, a generic text based on the resource type will be used.

As a convention, you must specify the resource type followed by the property (Title or Description) with a semicolon and the FHIR PATH expression based on which we extract the value.


Patient.Title: identifier

Note that in this example, identifier and are both collections that could contain more than one item. By default Simplifier only takes the first item of a collection. We built a custom FHIR PATH function to concatenate multiple items called glue(). The items are separated by the argument that is passed to this function.


Patient.Description:', ')

The description of the Patient resource would now show all names of the patient, seperated by a comma. It is also possible to take the first name of the patient only by adding [0] behind the element. Another possibility is to merge collections from different elements by using the | character. So, to show the first given name and the first family name sperated by a comma, you would get something like:

Patient.Description: (name[0].given[0] | name[0].family).glue(' ')

Note that the | character could also function as an OR operator as Simplifier will only select the first item in a collection. For example, say you want to show the name of an organization, but if name is empty you want to show the (first) identifier. You could use the following code to do so:

Organization.Title: name | identifier[0].value

In some cases, you may want to select the first item of a collection yourself, because you want to add additional text as well. In this situation, you could also use the first() function that is available in FHIR PATH.


PractitionerRole.Title: 'Role(s) of ' + (practitioner.display | practitioner.reference).first()

This example would show the value in the display element in the Reference to practitioner if available. If not available, it would show the value in the reference element. If none of these values is available, Simplifier would switch to the default value Example of a PractitionerRole that is defined in the core code.

There is a difference between using the + operator and the & operator to concatenate values. When the + operator is used and one of the values is empty, the complete result will be empty. When the & operator is used, it doesn’t matter if any of the values is empty. The remaining values will still be concatenated. So, if we would have used the & operator in the example above instead of the + operator and both practitioner.display and practitioner.reference would be empty, Simplifier would show the Title of the PractitionerRole resource as following: Role(s) of Which is of course not what we would want and the reason for using the + operator.

The editor supports comments as well. The comments are identified by using the # or // characters.


#Resource examples
Observation.Title: code.text
Profile.Description: description

For more information on how to use FHIR PATH, visit the following link to the FHIR PATH specification: