diff --git a/lib/api.rb b/lib/api.rb
index 2245cec63df..7e9891e027b 100644
--- a/lib/api.rb
+++ b/lib/api.rb
@@ -484,6 +484,7 @@ module Api
     # otherwise let HostUrl figure out what host is appropriate
     if self.respond_to?(:request)
       host, protocol = get_host_and_protocol_from_request
+      target_shard = Shard.current
     elsif self.respond_to?(:use_placeholder_host?) && use_placeholder_host?
       host = PLACEHOLDER_HOST
       protocol = PLACEHOLDER_PROTOCOL
@@ -505,7 +506,11 @@ module Api
     end
     html = rewriter.translate_content(html)
 
-    url_helper = Html::UrlProxy.new(self, context, host, protocol)
+    url_helper = Html::UrlProxy.new(self,
+                                    context,
+                                    host,
+                                    protocol,
+                                    target_shard: target_shard)
     account = Context.get_account(context) || @domain_root_account
     include_mobile = !(respond_to?(:in_app?, true) && in_app?)
     Html::Content.rewrite_outgoing(html, account, url_helper, include_mobile: include_mobile)
diff --git a/lib/api/html/url_proxy.rb b/lib/api/html/url_proxy.rb
index 1dfd9654396..2481a3edc70 100644
--- a/lib/api/html/url_proxy.rb
+++ b/lib/api/html/url_proxy.rb
@@ -75,12 +75,13 @@ module Api
     }.freeze
 
     class UrlProxy
-      attr_reader :proxy, :context, :host, :protocol
-      def initialize(helper, context, host, protocol)
+      attr_reader :proxy, :context, :host, :protocol, :target_shard
+      def initialize(helper, context, host, protocol, target_shard: nil)
         @proxy = helper
         @context = context
         @host = host
         @protocol = protocol
+        @target_shard = target_shard || context.shard
       end
 
       def media_object_thumbnail_url(media_id)
@@ -119,7 +120,15 @@ module Api
             # otherwise if it starts with a slash, it's a path that needs to be
             # made absolute with the canvas hostname prepended
             if !url.host && url_str[0] == '/'[0]
-              element[attribute] = "#{protocol}://#{host}#{url_str}"
+              # transpose IDs in the URL
+              if context.shard != target_shard && (args = recognize_path(url_str))
+                transpose_ids(args)
+                args[:host] = host
+                args[:protocol] = protocol
+                element[attribute] = proxy.url_for(args)
+              else
+                element[attribute] = "#{protocol}://#{host}#{url_str}"
+              end
               api_endpoint_info(url_str).each do |att, val|
                 element[att] = val
               end
@@ -138,6 +147,8 @@ module Api
           helper = api_route[1]
           args = { :protocol => protocol, :host => host }
           args.merge! Hash[api_route.slice(2, match.captures.size).zip match.captures]
+          # transpose IDs in the URL
+          transpose_ids(args) if context.shard != target_shard
           if args[:url] && (return_type == 'SessionlessLaunchUrl' || (return_type == "Page" && url.include?("titleize=0")))
             args[:url] = URI.unescape(args[:url])
           end
@@ -146,6 +157,44 @@ module Api
         end
         {}
       end
+
+      # based on ActionDispatch::Routing::RouteSet#recognize_path, but returning all params,
+      # not just path_params. and failures return nil, not raise an exception
+      def recognize_path(path)
+        path = ActionDispatch::Journey::Router::Utils.normalize_path(path)
+
+        begin
+          env = Rack::MockRequest.env_for(path, method: "GET")
+        rescue URI::InvalidURIError
+          return nil
+        end
+
+        req = Rails.application.routes.send(:make_request, env)
+        Rails.application.routes.router.recognize(req) do |route, params|
+          params.each do |key, value|
+            if value.is_a?(String)
+              value = value.dup.force_encoding(Encoding::BINARY)
+              params[key] = URI.parser.unescape(value)
+            end
+          end
+          req.path_parameters = params
+          app = route.app
+          if app.matches?(req) && app.dispatcher?
+            return req.params
+          end
+        end
+
+        nil
+      end
+
+      def transpose_ids(args)
+        args.each_key do |key|
+          if (key.to_s == 'id' || key.to_s.end_with?('_id')) &&
+            (new_id = Switchman::Shard.relative_id_for(args[key], context.shard, target_shard))
+            args[key] = Switchman::Shard.short_id_for(new_id)
+          end
+        end
+      end
     end
   end
 end
diff --git a/spec/lib/api/html/content_spec.rb b/spec/lib/api/html/content_spec.rb
index e0efd2557b1..8a49088fede 100644
--- a/spec/lib/api/html/content_spec.rb
+++ b/spec/lib/api/html/content_spec.rb
@@ -97,7 +97,7 @@ module Api
 
         it "re-writes root-relative urls to be absolute" do
           string = "<p><a href=\"/blah\"></a></p>"
-          url_helper = UrlProxy.new(double, double, "example.com", "https")
+          url_helper = UrlProxy.new(double, double(shard: nil), "example.com", "https")
           html = Content.new(string).rewritten_html(url_helper)
           expect(html).to eq("<p><a href=\"https://example.com/blah\"></a></p>")
         end
diff --git a/spec/lib/api_spec.rb b/spec/lib/api_spec.rb
index 50bb21bbaf4..5cdf34c761f 100644
--- a/spec/lib/api_spec.rb
+++ b/spec/lib/api_spec.rb
@@ -743,6 +743,35 @@ describe Api do
         expect(res).to eq "<p>a</p><p>b</p>"
       end
     end
+
+    context "sharding" do
+      specs_require_sharding
+
+      it 'transposes ids in urls' do
+        @shard1.activate do
+          a = Account.create!
+          student_in_course(account: a)
+        end
+        html = <<-HTML
+<img src="/courses/34/files/2082/download?wrap=1" data-api-returntype="File" data-api-endpoint="https://canvas.vanity.edu/api/v1/courses/34/files/2082">
+<a href="/courses/34/pages/module-1" data-api-returntype="Page" data-api-endpoint="https://canvas.vanity.edu/api/v1/courses/34/pages/module-1">link</a>
+        HTML
+
+        @k = klass.new
+        @k.instance_variable_set(:@domain_root_account, Account.default)
+        @k.extend Rails.application.routes.url_helpers
+        @k.extend ActionDispatch::Routing::UrlFor
+        allow(@k).to receive(:request).and_return(nil)
+        allow(@k).to receive(:get_host_and_protocol_from_request).and_return(['school.instructure.com', 'https'])
+        allow(@k).to receive(:url_options).and_return({})
+
+        res = @k.api_user_content(html, @course, @student)
+        expect(res).to eq <<-HTML
+<img src="https://school.instructure.com/courses/#{@shard1.id}~34/files/#{@shard1.id}~2082/download?wrap=1" data-api-returntype="File" data-api-endpoint="https://school.instructure.com/api/v1/courses/#{@shard1.id}~34/files/#{@shard1.id}~2082">
+<a href="https://school.instructure.com/courses/#{@shard1.id}~34/pages/module-1" data-api-returntype="Page" data-api-endpoint="https://school.instructure.com/api/v1/courses/#{@shard1.id}~34/pages/module-1">link</a>
+        HTML
+      end
+    end
   end
 
   context ".process_incoming_html_content" do