diff --git a/Directory.Build.props b/Directory.Build.props
index 4afdb32c..deb1a75f 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -64,6 +64,15 @@
     <Serviceable>false</Serviceable>
   </PropertyGroup>
 
+  <ItemGroup>
+    <!--
+      Note: OpenIddict uses PolySharp to dynamically generate polyfills for types that are not available on
+      some of the targeted TFMs (e.g Index, Range or nullable attributes on .NET Framework/.NET Standard).
+    -->
+    <PackageReference Include="PolySharp" Version="1.3.0" IsImplicitlyDefined="true"
+                      PrivateAssets="all" Condition=" '$(DisablePolySharp)' != 'true' " />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectCapability Include="DynamicDependentFile" />
     <ProjectCapability Include="DynamicFileNesting" />
diff --git a/gen/OpenIddict.Client.WebIntegration.Generators/OpenIddictClientWebIntegrationGenerator.cs b/gen/OpenIddict.Client.WebIntegration.Generators/OpenIddictClientWebIntegrationGenerator.cs
index 8a2a228e..3245ff2d 100644
--- a/gen/OpenIddict.Client.WebIntegration.Generators/OpenIddictClientWebIntegrationGenerator.cs
+++ b/gen/OpenIddict.Client.WebIntegration.Generators/OpenIddictClientWebIntegrationGenerator.cs
@@ -346,7 +346,7 @@ public partial class OpenIddictClientWebIntegrationBuilder
 
                                 Collection = (bool?) setting.Attribute("Collection") ?? false,
                                 Description = (string) setting.Attribute("Description") is string description ?
-                                    char.ToLower(description[0], CultureInfo.GetCultureInfo("en-US")) + description.Substring(1) : null,
+                                    char.ToLower(description[0], CultureInfo.GetCultureInfo("en-US")) + description[1..] : null,
                                 ClrType = (string) setting.Attribute("Type") switch
                                 {
                                     "EncryptionKey" when (string) setting.Element("EncryptionAlgorithm").Attribute("Value")
@@ -875,7 +875,7 @@ public partial class OpenIddictClientWebIntegrationOptions
 
                                 Collection = (bool?) setting.Attribute("Collection") ?? false,
                                 Description = (string) setting.Attribute("Description") is string description ?
-                                    char.ToLower(description[0], CultureInfo.GetCultureInfo("en-US")) + description.Substring(1) : null,
+                                    char.ToLower(description[0], CultureInfo.GetCultureInfo("en-US")) + description[1..] : null,
                                 ClrType = (string) setting.Attribute("Type") switch
                                 {
                                     "EncryptionKey" when (string) setting.Element("EncryptionAlgorithm").Attribute("Value")
diff --git a/sandbox/OpenIddict.Sandbox.AspNet.Client/OpenIddict.Sandbox.AspNet.Client.csproj b/sandbox/OpenIddict.Sandbox.AspNet.Client/OpenIddict.Sandbox.AspNet.Client.csproj
index 11172833..6bbb6812 100644
--- a/sandbox/OpenIddict.Sandbox.AspNet.Client/OpenIddict.Sandbox.AspNet.Client.csproj
+++ b/sandbox/OpenIddict.Sandbox.AspNet.Client/OpenIddict.Sandbox.AspNet.Client.csproj
@@ -8,6 +8,7 @@
     <MvcBuildViews>false</MvcBuildViews>
     <ImplicitUsings>disable</ImplicitUsings>
     <NoWarn>CA3147</NoWarn>
+    <DisablePolySharp>true</DisablePolySharp>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/sandbox/OpenIddict.Sandbox.AspNet.Server/OpenIddict.Sandbox.AspNet.Server.csproj b/sandbox/OpenIddict.Sandbox.AspNet.Server/OpenIddict.Sandbox.AspNet.Server.csproj
index c8011677..ef09766b 100644
--- a/sandbox/OpenIddict.Sandbox.AspNet.Server/OpenIddict.Sandbox.AspNet.Server.csproj
+++ b/sandbox/OpenIddict.Sandbox.AspNet.Server/OpenIddict.Sandbox.AspNet.Server.csproj
@@ -8,6 +8,7 @@
     <MvcBuildViews>false</MvcBuildViews>
     <ImplicitUsings>disable</ImplicitUsings>
     <NoWarn>CA3147</NoWarn>
+    <DisablePolySharp>true</DisablePolySharp>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/OpenIddict.Client.Owin/OpenIddictClientOwinHandlers.cs b/src/OpenIddict.Client.Owin/OpenIddictClientOwinHandlers.cs
index 4ece2246..7a7cb931 100644
--- a/src/OpenIddict.Client.Owin/OpenIddictClientOwinHandlers.cs
+++ b/src/OpenIddict.Client.Owin/OpenIddictClientOwinHandlers.cs
@@ -506,22 +506,22 @@ public static partial class OpenIddictClientOwinHandlers
                 {
                     // If the property ends with #string, represent it as a string parameter.
                     string key when key.EndsWith(PropertyTypes.String, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.String.Length),
+                        Name: key[..^PropertyTypes.String.Length],
                         Value: new OpenIddictParameter(property.Value)),
 
                     // If the property ends with #boolean, return it as a boolean parameter.
                     string key when key.EndsWith(PropertyTypes.Boolean, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Boolean.Length),
+                        Name: key[..^PropertyTypes.Boolean.Length],
                         Value: new OpenIddictParameter(bool.Parse(property.Value))),
 
                     // If the property ends with #integer, return it as an integer parameter.
                     string key when key.EndsWith(PropertyTypes.Integer, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Integer.Length),
+                        Name: key[..^PropertyTypes.Integer.Length],
                         Value: new OpenIddictParameter(long.Parse(property.Value, CultureInfo.InvariantCulture))),
 
                     // If the property ends with #json, return it as a JSON parameter.
                     string key when key.EndsWith(PropertyTypes.Json, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Json.Length),
+                        Name: key[..^PropertyTypes.Json.Length],
                         Value: new OpenIddictParameter(JsonSerializer.Deserialize<JsonElement>(property.Value))),
 
                     _ => default
@@ -706,22 +706,22 @@ public static partial class OpenIddictClientOwinHandlers
                 {
                     // If the property ends with #string, represent it as a string parameter.
                     string key when key.EndsWith(PropertyTypes.String, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.String.Length),
+                        Name: key[..^PropertyTypes.String.Length],
                         Value: new OpenIddictParameter(property.Value)),
 
                     // If the property ends with #boolean, return it as a boolean parameter.
                     string key when key.EndsWith(PropertyTypes.Boolean, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Boolean.Length),
+                        Name: key[..^PropertyTypes.Boolean.Length],
                         Value: new OpenIddictParameter(bool.Parse(property.Value))),
 
                     // If the property ends with #integer, return it as an integer parameter.
                     string key when key.EndsWith(PropertyTypes.Integer, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Integer.Length),
+                        Name: key[..^PropertyTypes.Integer.Length],
                         Value: new OpenIddictParameter(long.Parse(property.Value, CultureInfo.InvariantCulture))),
 
                     // If the property ends with #json, return it as a JSON parameter.
                     string key when key.EndsWith(PropertyTypes.Json, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Json.Length),
+                        Name: key[..^PropertyTypes.Json.Length],
                         Value: new OpenIddictParameter(JsonSerializer.Deserialize<JsonElement>(property.Value))),
 
                     _ => default
diff --git a/src/OpenIddict.Client/OpenIddictClientConfiguration.cs b/src/OpenIddict.Client/OpenIddictClientConfiguration.cs
index ef841b56..26cdbe1c 100644
--- a/src/OpenIddict.Client/OpenIddictClientConfiguration.cs
+++ b/src/OpenIddict.Client/OpenIddictClientConfiguration.cs
@@ -82,8 +82,7 @@ public class OpenIddictClientConfiguration : IPostConfigureOptions<OpenIddictCli
 
                         if (registration.MetadataAddress.OriginalString.StartsWith("/", StringComparison.Ordinal))
                         {
-                            registration.MetadataAddress = new Uri(registration.MetadataAddress.OriginalString.Substring(
-                                1, registration.MetadataAddress.OriginalString.Length - 1), UriKind.Relative);
+                            registration.MetadataAddress = new Uri(registration.MetadataAddress.OriginalString[1..], UriKind.Relative);
                         }
 
                         registration.MetadataAddress = new Uri(issuer, registration.MetadataAddress);
@@ -196,7 +195,7 @@ public class OpenIddictClientConfiguration : IPostConfigureOptions<OpenIddictCli
 
                 // Only use the 40 first chars of the base64url-encoded modulus.
                 var identifier = Base64UrlEncoder.Encode(parameters.Modulus);
-                return identifier.Substring(0, Math.Min(identifier.Length, 40)).ToUpperInvariant();
+                return identifier[..Math.Min(identifier.Length, 40)].ToUpperInvariant();
             }
 
 #if SUPPORTS_ECDSA
@@ -209,7 +208,7 @@ public class OpenIddictClientConfiguration : IPostConfigureOptions<OpenIddictCli
 
                 // Only use the 40 first chars of the base64url-encoded X coordinate.
                 var identifier = Base64UrlEncoder.Encode(parameters.Q.X);
-                return identifier.Substring(0, Math.Min(identifier.Length, 40)).ToUpperInvariant();
+                return identifier[..Math.Min(identifier.Length, 40)].ToUpperInvariant();
             }
 #endif
 
diff --git a/src/OpenIddict.Client/OpenIddictClientHandlers.Protection.cs b/src/OpenIddict.Client/OpenIddictClientHandlers.Protection.cs
index e5b221f1..aa092e24 100644
--- a/src/OpenIddict.Client/OpenIddictClientHandlers.Protection.cs
+++ b/src/OpenIddict.Client/OpenIddictClientHandlers.Protection.cs
@@ -119,7 +119,7 @@ public static partial class OpenIddictClientHandlers
                         { AbsolutePath: "/", Query.Length: 0, Fragment.Length: 0 } issuer => new[]
                         {
                             issuer.AbsoluteUri, // Uri.AbsoluteUri is normalized and always contains a trailing slash.
-                            issuer.AbsoluteUri.Substring(0, issuer.AbsoluteUri.Length - 1)
+                            issuer.AbsoluteUri[..^1]
                         },
 
                         Uri issuer => new[] { issuer.AbsoluteUri }
diff --git a/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs b/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs
index d072cea2..408033c8 100644
--- a/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs
+++ b/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs
@@ -1433,10 +1433,10 @@ public class OpenIddictApplicationManager<TApplication> : IOpenIddictApplication
             BinaryPrimitives.WriteUInt32BigEndian(payload.Slice(9, 12), (uint) salt.Length);
 
             // Write the salt.
-            salt.CopyTo(payload.Slice(13));
+            salt.CopyTo(payload[13..]);
 
             // Write the subkey.
-            key.CopyTo(payload.Slice(13 + salt.Length));
+            key.CopyTo(payload[(13 + salt.Length)..]);
 
             return payload;
         }
diff --git a/src/OpenIddict.EntityFramework.Models/OpenIddict.EntityFramework.Models.csproj b/src/OpenIddict.EntityFramework.Models/OpenIddict.EntityFramework.Models.csproj
index ab3fb342..587e7da4 100644
--- a/src/OpenIddict.EntityFramework.Models/OpenIddict.EntityFramework.Models.csproj
+++ b/src/OpenIddict.EntityFramework.Models/OpenIddict.EntityFramework.Models.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFrameworks>net461;netstandard2.0</TargetFrameworks>
+    <DisablePolySharp>true</DisablePolySharp>
   </PropertyGroup>
 
   <PropertyGroup>
diff --git a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddict.EntityFrameworkCore.Models.csproj b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddict.EntityFrameworkCore.Models.csproj
index 6a59bf7a..f7bf28c4 100644
--- a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddict.EntityFrameworkCore.Models.csproj
+++ b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddict.EntityFrameworkCore.Models.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFrameworks>net461;netstandard2.0</TargetFrameworks>
+    <DisablePolySharp>true</DisablePolySharp>
   </PropertyGroup>
 
   <PropertyGroup>
diff --git a/src/OpenIddict.MongoDb.Models/OpenIddict.MongoDb.Models.csproj b/src/OpenIddict.MongoDb.Models/OpenIddict.MongoDb.Models.csproj
index 439170e5..eb28110b 100644
--- a/src/OpenIddict.MongoDb.Models/OpenIddict.MongoDb.Models.csproj
+++ b/src/OpenIddict.MongoDb.Models/OpenIddict.MongoDb.Models.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFrameworks>net461;netstandard2.0</TargetFrameworks>
+    <DisablePolySharp>true</DisablePolySharp>
     <SignAssembly>false</SignAssembly>
     <PublicSign>false</PublicSign>
   </PropertyGroup>
diff --git a/src/OpenIddict.Server.AspNetCore/OpenIddictServerAspNetCoreHandlers.cs b/src/OpenIddict.Server.AspNetCore/OpenIddictServerAspNetCoreHandlers.cs
index e30763eb..0e7d00c7 100644
--- a/src/OpenIddict.Server.AspNetCore/OpenIddictServerAspNetCoreHandlers.cs
+++ b/src/OpenIddict.Server.AspNetCore/OpenIddictServerAspNetCoreHandlers.cs
@@ -760,7 +760,7 @@ public static partial class OpenIddictServerAspNetCoreHandlers
 
             try
             {
-                var value = header.Substring("Basic ".Length).Trim();
+                var value = header["Basic ".Length..].Trim();
                 var data = Encoding.ASCII.GetString(Convert.FromBase64String(value));
 
                 var index = data.IndexOf(':');
@@ -775,8 +775,8 @@ public static partial class OpenIddictServerAspNetCoreHandlers
                 }
 
                 // Attach the basic authentication credentials to the request message.
-                context.Transaction.Request.ClientId = UnescapeDataString(data.Substring(0, index));
-                context.Transaction.Request.ClientSecret = UnescapeDataString(data.Substring(index + 1));
+                context.Transaction.Request.ClientId = UnescapeDataString(data[..index]);
+                context.Transaction.Request.ClientSecret = UnescapeDataString(data[(index + 1)..]);
 
                 return default;
             }
@@ -843,7 +843,7 @@ public static partial class OpenIddictServerAspNetCoreHandlers
             }
 
             // Attach the access token to the request message.
-            context.Transaction.Request.AccessToken = header.Substring("Bearer ".Length);
+            context.Transaction.Request.AccessToken = header["Bearer ".Length..];
 
             return default;
         }
diff --git a/src/OpenIddict.Server.Owin/OpenIddictServerOwinHandlers.cs b/src/OpenIddict.Server.Owin/OpenIddictServerOwinHandlers.cs
index 56b046e0..2ea020ab 100644
--- a/src/OpenIddict.Server.Owin/OpenIddictServerOwinHandlers.cs
+++ b/src/OpenIddict.Server.Owin/OpenIddictServerOwinHandlers.cs
@@ -318,22 +318,22 @@ public static partial class OpenIddictServerOwinHandlers
                 {
                     // If the property ends with #string, represent it as a string parameter.
                     string key when key.EndsWith(PropertyTypes.String, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.String.Length),
+                        Name: key[..^PropertyTypes.String.Length],
                         Value: new OpenIddictParameter(property.Value)),
 
                     // If the property ends with #boolean, return it as a boolean parameter.
                     string key when key.EndsWith(PropertyTypes.Boolean, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Boolean.Length),
+                        Name: key[..^PropertyTypes.Boolean.Length],
                         Value: new OpenIddictParameter(bool.Parse(property.Value))),
 
                     // If the property ends with #integer, return it as an integer parameter.
                     string key when key.EndsWith(PropertyTypes.Integer, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Integer.Length),
+                        Name: key[..^PropertyTypes.Integer.Length],
                         Value: new OpenIddictParameter(long.Parse(property.Value, CultureInfo.InvariantCulture))),
 
                     // If the property ends with #json, return it as a JSON parameter.
                     string key when key.EndsWith(PropertyTypes.Json, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Json.Length),
+                        Name: key[..^PropertyTypes.Json.Length],
                         Value: new OpenIddictParameter(JsonSerializer.Deserialize<JsonElement>(property.Value))),
 
                     _ => default
@@ -438,22 +438,22 @@ public static partial class OpenIddictServerOwinHandlers
                 {
                     // If the property ends with #string, represent it as a string parameter.
                     string key when key.EndsWith(PropertyTypes.String, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.String.Length),
+                        Name: key[..^PropertyTypes.String.Length],
                         Value: new OpenIddictParameter(property.Value)),
 
                     // If the property ends with #boolean, return it as a boolean parameter.
                     string key when key.EndsWith(PropertyTypes.Boolean, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Boolean.Length),
+                        Name: key[..^PropertyTypes.Boolean.Length],
                         Value: new OpenIddictParameter(bool.Parse(property.Value))),
 
                     // If the property ends with #integer, return it as an integer parameter.
                     string key when key.EndsWith(PropertyTypes.Integer, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Integer.Length),
+                        Name: key[..^PropertyTypes.Integer.Length],
                         Value: new OpenIddictParameter(long.Parse(property.Value, CultureInfo.InvariantCulture))),
 
                     // If the property ends with #json, return it as a JSON parameter.
                     string key when key.EndsWith(PropertyTypes.Json, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Json.Length),
+                        Name: key[..^PropertyTypes.Json.Length],
                         Value: new OpenIddictParameter(JsonSerializer.Deserialize<JsonElement>(property.Value))),
 
                     _ => default
@@ -517,22 +517,22 @@ public static partial class OpenIddictServerOwinHandlers
                 {
                     // If the property ends with #string, represent it as a string parameter.
                     string key when key.EndsWith(PropertyTypes.String, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.String.Length),
+                        Name: key[..^PropertyTypes.String.Length],
                         Value: new OpenIddictParameter(property.Value)),
 
                     // If the property ends with #boolean, return it as a boolean parameter.
                     string key when key.EndsWith(PropertyTypes.Boolean, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Boolean.Length),
+                        Name: key[..^PropertyTypes.Boolean.Length],
                         Value: new OpenIddictParameter(bool.Parse(property.Value))),
 
                     // If the property ends with #integer, return it as an integer parameter.
                     string key when key.EndsWith(PropertyTypes.Integer, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Integer.Length),
+                        Name: key[..^PropertyTypes.Integer.Length],
                         Value: new OpenIddictParameter(long.Parse(property.Value, CultureInfo.InvariantCulture))),
 
                     // If the property ends with #json, return it as a JSON parameter.
                     string key when key.EndsWith(PropertyTypes.Json, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Json.Length),
+                        Name: key[..^PropertyTypes.Json.Length],
                         Value: new OpenIddictParameter(JsonSerializer.Deserialize<JsonElement>(property.Value))),
 
                     _ => default
@@ -815,7 +815,7 @@ public static partial class OpenIddictServerOwinHandlers
 
             try
             {
-                var value = header.Substring("Basic ".Length).Trim();
+                var value = header["Basic ".Length..].Trim();
                 var data = Encoding.ASCII.GetString(Convert.FromBase64String(value));
 
                 var index = data.IndexOf(':');
@@ -830,8 +830,8 @@ public static partial class OpenIddictServerOwinHandlers
                 }
 
                 // Attach the basic authentication credentials to the request message.
-                context.Transaction.Request.ClientId = UnescapeDataString(data.Substring(0, index));
-                context.Transaction.Request.ClientSecret = UnescapeDataString(data.Substring(index + 1));
+                context.Transaction.Request.ClientId = UnescapeDataString(data[..index]);
+                context.Transaction.Request.ClientSecret = UnescapeDataString(data[(index + 1)..]);
 
                 return default;
             }
@@ -898,7 +898,7 @@ public static partial class OpenIddictServerOwinHandlers
             }
 
             // Attach the access token to the request message.
-            context.Transaction.Request.AccessToken = header.Substring("Bearer ".Length);
+            context.Transaction.Request.AccessToken = header["Bearer ".Length..];
 
             return default;
         }
diff --git a/src/OpenIddict.Server/OpenIddictServerConfiguration.cs b/src/OpenIddict.Server/OpenIddictServerConfiguration.cs
index a5a4770d..5768572b 100644
--- a/src/OpenIddict.Server/OpenIddictServerConfiguration.cs
+++ b/src/OpenIddict.Server/OpenIddictServerConfiguration.cs
@@ -318,7 +318,7 @@ public class OpenIddictServerConfiguration : IPostConfigureOptions<OpenIddictSer
 
                 // Only use the 40 first chars of the base64url-encoded modulus.
                 var identifier = Base64UrlEncoder.Encode(parameters.Modulus);
-                return identifier.Substring(0, Math.Min(identifier.Length, 40)).ToUpperInvariant();
+                return identifier[..Math.Min(identifier.Length, 40)].ToUpperInvariant();
             }
 
 #if SUPPORTS_ECDSA
@@ -331,7 +331,7 @@ public class OpenIddictServerConfiguration : IPostConfigureOptions<OpenIddictSer
 
                 // Only use the 40 first chars of the base64url-encoded X coordinate.
                 var identifier = Base64UrlEncoder.Encode(parameters.Q.X);
-                return identifier.Substring(0, Math.Min(identifier.Length, 40)).ToUpperInvariant();
+                return identifier[..Math.Min(identifier.Length, 40)].ToUpperInvariant();
             }
 #endif
 
diff --git a/src/OpenIddict.Server/OpenIddictServerHandlers.Authentication.cs b/src/OpenIddict.Server/OpenIddictServerHandlers.Authentication.cs
index 2341c95c..cd4da7c9 100644
--- a/src/OpenIddict.Server/OpenIddictServerHandlers.Authentication.cs
+++ b/src/OpenIddict.Server/OpenIddictServerHandlers.Authentication.cs
@@ -1487,9 +1487,7 @@ public static partial class OpenIddictServerHandlers
 
                         // Note: response types can be specified in any order. To ensure permissions are correctly
                         // checked even if the order differs from the one specified in the request, a HashSet is used.
-                        var values = permission.Substring(prefix.Length, permission.Length - prefix.Length)
-                                               .Split(Separators.Space, StringSplitOptions.RemoveEmptyEntries);
-
+                        var values = permission[prefix.Length..].Split(Separators.Space, StringSplitOptions.RemoveEmptyEntries);
                         if (values.Length is not 0 && new HashSet<string>(values, StringComparer.Ordinal).SetEquals(types))
                         {
                             return true;
diff --git a/src/OpenIddict.Server/OpenIddictServerHandlers.Discovery.cs b/src/OpenIddict.Server/OpenIddictServerHandlers.Discovery.cs
index 7c90f303..fd0d583a 100644
--- a/src/OpenIddict.Server/OpenIddictServerHandlers.Discovery.cs
+++ b/src/OpenIddict.Server/OpenIddictServerHandlers.Discovery.cs
@@ -393,7 +393,7 @@ public static partial class OpenIddictServerHandlers
                     // for Uri's constructor to correctly compute correct absolute URLs.
                     if (endpoint.OriginalString.StartsWith("/", StringComparison.Ordinal))
                     {
-                        endpoint = new Uri(endpoint.OriginalString.Substring(1, endpoint.OriginalString.Length - 1), UriKind.Relative);
+                        endpoint = new Uri(endpoint.OriginalString[1..], UriKind.Relative);
                     }
 
                     return new Uri(issuer, endpoint);
diff --git a/src/OpenIddict.Server/OpenIddictServerHandlers.cs b/src/OpenIddict.Server/OpenIddictServerHandlers.cs
index dd58baa7..6654e7e0 100644
--- a/src/OpenIddict.Server/OpenIddictServerHandlers.cs
+++ b/src/OpenIddict.Server/OpenIddictServerHandlers.cs
@@ -3056,7 +3056,7 @@ public static partial class OpenIddictServerHandlers
                 // for Uri's constructor to correctly compute correct absolute URLs.
                 if (endpoint.OriginalString.StartsWith("/", StringComparison.Ordinal))
                 {
-                    endpoint = new Uri(endpoint.OriginalString.Substring(1, endpoint.OriginalString.Length - 1), UriKind.Relative);
+                    endpoint = new Uri(endpoint.OriginalString[1..], UriKind.Relative);
                 }
 
                 return new Uri(issuer, endpoint);
diff --git a/src/OpenIddict.Validation.AspNetCore/OpenIddictValidationAspNetCoreHandlers.cs b/src/OpenIddict.Validation.AspNetCore/OpenIddictValidationAspNetCoreHandlers.cs
index 43eec9e5..e6888563 100644
--- a/src/OpenIddict.Validation.AspNetCore/OpenIddictValidationAspNetCoreHandlers.cs
+++ b/src/OpenIddict.Validation.AspNetCore/OpenIddictValidationAspNetCoreHandlers.cs
@@ -163,7 +163,7 @@ public static partial class OpenIddictValidationAspNetCoreHandlers
             string? header = request.Headers[HeaderNames.Authorization];
             if (!string.IsNullOrEmpty(header) && header.StartsWith("Bearer ", StringComparison.OrdinalIgnoreCase))
             {
-                context.AccessToken = header.Substring("Bearer ".Length);
+                context.AccessToken = header["Bearer ".Length..];
 
                 return default;
             }
diff --git a/src/OpenIddict.Validation.Owin/OpenIddictValidationOwinHandlers.cs b/src/OpenIddict.Validation.Owin/OpenIddictValidationOwinHandlers.cs
index aa44e9e3..0e1724af 100644
--- a/src/OpenIddict.Validation.Owin/OpenIddictValidationOwinHandlers.cs
+++ b/src/OpenIddict.Validation.Owin/OpenIddictValidationOwinHandlers.cs
@@ -163,7 +163,7 @@ public static partial class OpenIddictValidationOwinHandlers
             string header = request.Headers[Headers.Authorization];
             if (!string.IsNullOrEmpty(header) && header.StartsWith("Bearer ", StringComparison.OrdinalIgnoreCase))
             {
-                context.AccessToken = header.Substring("Bearer ".Length);
+                context.AccessToken = header["Bearer ".Length..];
 
                 return default;
             }
@@ -322,22 +322,22 @@ public static partial class OpenIddictValidationOwinHandlers
                 {
                     // If the property ends with #string, represent it as a string parameter.
                     string key when key.EndsWith(PropertyTypes.String, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.String.Length),
+                        Name: key[..^PropertyTypes.String.Length],
                         Value: new OpenIddictParameter(property.Value)),
 
                     // If the property ends with #boolean, return it as a boolean parameter.
                     string key when key.EndsWith(PropertyTypes.Boolean, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Boolean.Length),
+                        Name: key[..^PropertyTypes.Boolean.Length],
                         Value: new OpenIddictParameter(bool.Parse(property.Value))),
 
                     // If the property ends with #integer, return it as an integer parameter.
                     string key when key.EndsWith(PropertyTypes.Integer, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Integer.Length),
+                        Name: key[..^PropertyTypes.Integer.Length],
                         Value: new OpenIddictParameter(long.Parse(property.Value, CultureInfo.InvariantCulture))),
 
                     // If the property ends with #json, return it as a JSON parameter.
                     string key when key.EndsWith(PropertyTypes.Json, StringComparison.OrdinalIgnoreCase) => (
-                        Name: key.Substring(0, key.Length - PropertyTypes.Json.Length),
+                        Name: key[..^PropertyTypes.Json.Length],
                         Value: new OpenIddictParameter(JsonSerializer.Deserialize<JsonElement>(property.Value))),
 
                     _ => default
diff --git a/src/OpenIddict.Validation/OpenIddictValidationConfiguration.cs b/src/OpenIddict.Validation/OpenIddictValidationConfiguration.cs
index 00f81e34..b23dabea 100644
--- a/src/OpenIddict.Validation/OpenIddictValidationConfiguration.cs
+++ b/src/OpenIddict.Validation/OpenIddictValidationConfiguration.cs
@@ -126,8 +126,7 @@ public class OpenIddictValidationConfiguration : IPostConfigureOptions<OpenIddic
 
                     if (options.MetadataAddress.OriginalString.StartsWith("/", StringComparison.Ordinal))
                     {
-                        options.MetadataAddress = new Uri(options.MetadataAddress.OriginalString.Substring(
-                            1, options.MetadataAddress.OriginalString.Length - 1), UriKind.Relative);
+                        options.MetadataAddress = new Uri(options.MetadataAddress.OriginalString[1..], UriKind.Relative);
                     }
 
                     options.MetadataAddress = new Uri(issuer, options.MetadataAddress);
diff --git a/src/OpenIddict.Validation/OpenIddictValidationHandlers.Protection.cs b/src/OpenIddict.Validation/OpenIddictValidationHandlers.Protection.cs
index f8e80aef..9aa3e84b 100644
--- a/src/OpenIddict.Validation/OpenIddictValidationHandlers.Protection.cs
+++ b/src/OpenIddict.Validation/OpenIddictValidationHandlers.Protection.cs
@@ -73,7 +73,7 @@ public static partial class OpenIddictValidationHandlers
                     { AbsolutePath: "/", Query.Length: 0, Fragment.Length: 0 } issuer => new[]
                     {
                         issuer.AbsoluteUri, // Uri.AbsoluteUri is normalized and always contains a trailing slash.
-                        issuer.AbsoluteUri.Substring(0, issuer.AbsoluteUri.Length - 1)
+                        issuer.AbsoluteUri[..^1]
                     },
 
                     Uri issuer => new[] { issuer.AbsoluteUri }
diff --git a/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTestClient.cs b/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTestClient.cs
index d0c2ed3e..9ce0c4d9 100644
--- a/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTestClient.cs
+++ b/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTestClient.cs
@@ -435,13 +435,13 @@ public class OpenIddictServerIntegrationTestClient : IAsyncDisposable
                     continue;
                 }
 
-                var name = line.Substring(0, index);
+                var name = line[..index];
                 if (string.IsNullOrEmpty(name))
                 {
                     continue;
                 }
 
-                var value = line.Substring(index + 1);
+                var value = line[(index + 1)..];
 
                 parameters.Add(new KeyValuePair<string, string>(name, value));
             }
diff --git a/test/OpenIddict.Validation.IntegrationTests/OpenIddictValidationIntegrationTestClient.cs b/test/OpenIddict.Validation.IntegrationTests/OpenIddictValidationIntegrationTestClient.cs
index d1c2ae19..819e1454 100644
--- a/test/OpenIddict.Validation.IntegrationTests/OpenIddictValidationIntegrationTestClient.cs
+++ b/test/OpenIddict.Validation.IntegrationTests/OpenIddictValidationIntegrationTestClient.cs
@@ -435,13 +435,13 @@ public class OpenIddictValidationIntegrationTestClient : IAsyncDisposable
                     continue;
                 }
 
-                var name = line.Substring(0, index);
+                var name = line[..index];
                 if (string.IsNullOrEmpty(name))
                 {
                     continue;
                 }
 
-                var value = line.Substring(index + 1);
+                var value = line[(index + 1)..];
 
                 parameters.Add(new KeyValuePair<string, string>(name, value));
             }