With Open.IdentityServer we have internalised constants and helpers needed, meaning that references to an IdentityModel package are no longer needed.

Internalised Content from IdentityModel package

Original Full Class Name

New Full Class Name

IdentityModel.OidcConstants

Open.IdentityServer.OidcConstants

IdentityModel.JwtClaimTypes

Open.IdentityServer.JwtClaimTypes

IdentityModel.X509

Open.IdentityServer.Utility.X509.X509

IdentityModel.X509CertificatesFinder

Open.IdentityServer.Utility.X509.X509CertificatesFinder

IdentityModel.X509CertificatesLocation

Open.IdentityServer.Utility.X509.X509CertificatesLocation

IdentityModel.X509CertificatesName

Open.IdentityServer.Utility.X509.X509CertificatesName

IdentityModel.Base64Url

Open.IdentityServer.Utility.Base64Url

IdentityModel.ClaimComparer

Open.IdentityServer.ClaimComparer

IdentityModel.CryptoRandom

Open.IdentityServer.Utility.CryptoRandom

IdentityModel.Identity

Open.IdentityServer.Utility.Identity

IdentityModel.Principal

Open.IdentityServer.Utility.Principal

IdentityModel.StringExtensions

Open.IdentityServer.Utility.StringExtensions

IdentityModel.TimeConstantComparer

Open.IdentityServer.Utility.TimeConstantComparer

Recommendations for Client Side

For client-side applications, there are external 3rd party libraries available, including the Duende.IdentityModel free open-source package, which is the latest version of the package that IdentityServer4 used.