diff --git a/lib/pact_broker/api.rb b/lib/pact_broker/api.rb
index 00fcdf08e..a420b80f5 100644
--- a/lib/pact_broker/api.rb
+++ b/lib/pact_broker/api.rb
@@ -16,6 +16,8 @@ module PactBroker
         add ['pacts', 'provider', :provider_name, 'consumer', :consumer_name, 'pact-version', :pact_version_sha], Api::Resources::PactVersion, {resource_name: "pact_publication"}
         add ['pacts', 'provider', :provider_name, 'consumer', :consumer_name, 'version', :consumer_version_number, 'previous-distinct'], Api::Resources::PreviousDistinctPactVersion, {resource_name: "previous_distinct_pact_version"}
         add ['pacts', 'provider', :provider_name, 'consumer', :consumer_name, 'version', :consumer_version_number, 'diff', 'previous-distinct'], Api::Resources::PactContentDiff, {resource_name: "previous_distinct_pact_version_diff"}
+        add ['pacts', 'provider', :provider_name, 'consumer', :consumer_name, 'version', :consumer_version_number, 'diff', 'version', :comparison_consumer_version], Api::Resources::PactContentDiff, {resource_name: "pact_version_diff_by_consumer_version"}
+        add ['pacts', 'provider', :provider_name, 'consumer', :consumer_name, 'pact-version', :pact_version_sha, 'diff', 'pact-version', :comparison_pact_version_sha], Api::Resources::PactContentDiff, {resource_name: "pact_version_diff_by_pact_version_sha"}
 
         # Verifications
         add ['pacts', 'provider', :provider_name, 'consumer', :consumer_name, 'pact-version', :pact_version_sha, 'verification-results'], Api::Resources::Verifications, {resource_name: "verification_results"}
diff --git a/lib/pact_broker/api/resources/pact_content_diff.rb b/lib/pact_broker/api/resources/pact_content_diff.rb
index 3ac35a914..ac3d90f0d 100644
--- a/lib/pact_broker/api/resources/pact_content_diff.rb
+++ b/lib/pact_broker/api/resources/pact_content_diff.rb
@@ -20,7 +20,7 @@ def resource_exists?
         end
 
         def to_text
-          output = PactBroker::Pacts::Diff.new.process pact_params.merge(base_url: base_url)
+          output = PactBroker::Pacts::Diff.new.process pact_params.merge(base_url: base_url), comparison_pact_params, raw: false
           response.body = output
         end
 
@@ -29,7 +29,19 @@ def pact
         end
 
         def pact_params
-          @pact_params ||= PactBroker::Pacts::PactParams.from_request request, path_info
+          @pact_params ||= PactBroker::Pacts::PactParams.from_path_info identifier_from_path
+        end
+
+        def comparison_pact_params
+          if identifier_from_path[:comparison_consumer_version_number] || identifier_from_path[:comparison_pact_version_sha]
+            comparison_identifier_from_path = identifier_from_path.merge(
+                consumer_version_number: identifier_from_path[:comparison_consumer_version_number],
+                pact_version_sha: identifier_from_path[:comparison_pact_version_sha],
+                base_url: base_url)
+            PactBroker::Pacts::PactParams.from_path_info(comparison_identifier_from_path)
+          else
+            nil
+          end
         end
       end
     end
diff --git a/lib/pact_broker/pacts/diff.rb b/lib/pact_broker/pacts/diff.rb
index 3778a0be5..25ab8238c 100644
--- a/lib/pact_broker/pacts/diff.rb
+++ b/lib/pact_broker/pacts/diff.rb
@@ -1,6 +1,7 @@
 require 'pact_broker/api/pact_broker_urls'
 require 'pact_broker/date_helper'
 require 'pact_broker/pacts/create_formatted_diff'
+require 'pact_broker/pacts/sort_verifiable_content'
 require 'pact_broker/repositories'
 require 'yaml'
 
@@ -10,13 +11,13 @@ module Pacts
     class Diff
       include PactBroker::Repositories
 
-      def process(params)
+      def process(params, comparison_pact_params = nil, options = {})
         pact = find_pact(params)
-        previous_distinct_pact = pact_repository.find_previous_distinct_pact(pact)
+        comparison_pact = comparison_pact_params ? find_pact(comparison_pact_params) : pact_repository.find_previous_distinct_pact(pact)
 
-        if previous_distinct_pact
-          next_pact = pact_repository.find_next_pact(previous_distinct_pact)
-          DiffDecorator.new(pact, previous_distinct_pact, next_pact, params[:base_url]).to_text
+        if comparison_pact
+          next_pact = pact_repository.find_next_pact(comparison_pact) || pact
+          DiffDecorator.new(pact, comparison_pact, next_pact, params[:base_url], { raw: options[:raw] }).to_text
         else
           no_previous_version_message pact
         end
@@ -27,7 +28,8 @@ def process(params)
       def find_pact(params)
         pact_repository.find_pact(params.consumer_name,
                                   params.consumer_version_number,
-                                  params.provider_name)
+                                  params.provider_name,
+                                  params.pact_version_sha)
       end
 
       def no_previous_version_message(pact)
@@ -46,11 +48,12 @@ def no_previous_version_message(pact)
       # the latest distinct version content was first created.
 
       class DiffDecorator
-        def initialize(pact, previous_distinct_pact, next_pact, base_url)
+        def initialize(pact, comparison_pact, next_pact, base_url, options)
           @pact = pact
-          @previous_distinct_pact = previous_distinct_pact
+          @comparison_pact = comparison_pact
           @next_pact = next_pact
           @base_url = base_url
+          @options = options
         end
 
         def to_text
@@ -59,7 +62,7 @@ def to_text
 
         private
 
-        attr_reader :pact, :previous_distinct_pact, :next_pact, :base_url
+        attr_reader :pact, :comparison_pact, :next_pact, :base_url, :options
 
         def change_date_in_words
           DateHelper.local_date_in_words next_pact.created_at
@@ -70,7 +73,7 @@ def now
         end
 
         def header
-          title = "# Diff between versions #{previous_distinct_pact.consumer_version_number} and #{pact.consumer_version_number} of the pact between #{pact.consumer.name} and #{pact.provider.name}"
+          title = "# Diff between versions #{comparison_pact.consumer_version_number} and #{pact.consumer_version_number} of the pact between #{pact.consumer.name} and #{pact.provider.name}"
           description = "The following changes were made #{change_date_ago_in_words} ago (#{change_date_in_words})"
 
           title +  "\n\n" + description
@@ -78,7 +81,7 @@ def header
 
         def links
           self_url = PactBroker::Api::PactBrokerUrls.pact_url(base_url, pact)
-          previous_distinct_url = PactBroker::Api::PactBrokerUrls.pact_url(base_url, previous_distinct_pact)
+          previous_distinct_url = PactBroker::Api::PactBrokerUrls.pact_url(base_url, comparison_pact)
 
           links = {
             "current-pact-version" => {
@@ -88,7 +91,7 @@ def links
             },
             "previous-distinct-pact-version" => {
               "title" => "Pact",
-              "name" => previous_distinct_pact.name,
+              "name" => comparison_pact.name,
               "href" => previous_distinct_url
             }
           }
@@ -96,12 +99,20 @@ def links
         end
 
         def diff
-          CreateFormattedDiff.(pact.json_content, previous_distinct_pact.json_content)
+          CreateFormattedDiff.(prepare_content(pact.json_content), prepare_content(comparison_pact.json_content))
         end
 
         def change_date_ago_in_words
           DateHelper.distance_of_time_in_words next_pact.created_at, now
         end
+
+        def prepare_content json_content
+          if options[:raw]
+            json_content
+          else
+            PactBroker::Pacts::SortVerifiableContent.call(json_content)
+          end
+        end
       end
     end
   end
diff --git a/lib/pact_broker/pacts/pact_params.rb b/lib/pact_broker/pacts/pact_params.rb
index 06de93f26..456658ac2 100644
--- a/lib/pact_broker/pacts/pact_params.rb
+++ b/lib/pact_broker/pacts/pact_params.rb
@@ -10,6 +10,16 @@ def initialize attributes
         merge!(attributes)
       end
 
+      def self.from_path_info path_info
+        new(
+          consumer_name: path_info.fetch(:consumer_name),
+          provider_name: path_info.fetch(:provider_name),
+          consumer_version_number: path_info[:consumer_version_number],
+          revision_number: path_info[:revision_number],
+          pact_version_sha: path_info[:pact_version_sha]
+        )
+      end
+
       def self.from_request request, path_info
         json_content = request.body.to_s
         parsed_content = begin
diff --git a/lib/pact_broker/pacts/sort_verifiable_content.rb b/lib/pact_broker/pacts/sort_verifiable_content.rb
new file mode 100644
index 000000000..b9149e506
--- /dev/null
+++ b/lib/pact_broker/pacts/sort_verifiable_content.rb
@@ -0,0 +1,41 @@
+require 'pact_broker/json'
+
+module PactBroker
+  module Pacts
+    class SortVerifiableContent
+
+      def self.call json
+        hash = JSON.parse(json, PACT_PARSING_OPTIONS)
+        verifiable_content = if hash['interactions']
+          hash['interactions']
+        elsif hash['messages']
+          hash['messages']
+        end
+        order_verifiable_content(verifiable_content).to_json
+      end
+
+      def self.order_verifiable_content array
+        array_with_ordered_hashes = order_hashes(array)
+        array_with_ordered_hashes.sort{|a, b| a.to_json <=> b.to_json }
+      end
+
+      def self.order_hashes thing
+        case thing
+          when Hash then order_hash(thing)
+          when Array then order_child_array(thing)
+        else thing
+        end
+      end
+
+      def self.order_child_array array
+        array.collect{|thing| order_hashes(thing) }
+      end
+
+      def self.order_hash hash
+        hash.keys.sort.each_with_object({}) do | key, new_hash |
+          new_hash[key] = order_hashes(hash[key])
+        end
+      end
+    end
+  end
+end
diff --git a/spec/lib/pact_broker/pacts/diff_spec.rb b/spec/lib/pact_broker/pacts/diff_spec.rb
index c1287b50b..914f3409f 100644
--- a/spec/lib/pact_broker/pacts/diff_spec.rb
+++ b/spec/lib/pact_broker/pacts/diff_spec.rb
@@ -15,6 +15,19 @@ module Pacts
         end
         let(:pact_content_version_2) { load_fixture('consumer-provider.json') }
         let(:pact_content_version_3) { pact_content_version_2 }
+        let(:pact_content_version_4) do
+          hash = load_json_fixture('consumer-provider.json')
+          hash['interactions'].first['request']['method'] = 'delete'
+          hash.to_json
+        end
+
+        let(:pact_params) do
+          PactBroker::Pacts::PactParams.new(
+            consumer_name: 'Consumer',
+            provider_name: 'Provider',
+            consumer_version_number: '3'
+          )
+        end
 
         before do
           TestDataBuilder.new
@@ -26,21 +39,36 @@ module Pacts
             .create_pact(json_content: pact_content_version_2)
             .create_consumer_version("3")
             .create_pact(json_content: pact_content_version_3)
+            .create_consumer_version("4")
+            .create_pact(json_content: pact_content_version_4)
+
           allow(DateHelper).to receive(:local_date_in_words).and_return("a date")
         end
 
-        subject { Diff.new.process(pact_params.merge(base_url: 'http://example.org')) }
-
-        context "when there is a previous distinct version" do
+        subject { Diff.new.process(pact_params.merge(base_url: 'http://example.org'), nil, raw: true) }
 
-          let(:pact_params) do
+        context "when a comparison version is specified" do
+          let(:comparison_pact_params) do
             PactBroker::Pacts::PactParams.new(
               consumer_name: 'Consumer',
               provider_name: 'Provider',
-              consumer_version_number: '3'
-            )
+              consumer_version_number: '4'
+            ).merge(base_url: 'http://example.org')
           end
 
+          subject { Diff.new.process(pact_params.merge(base_url: 'http://example.org'), comparison_pact_params) }
+
+          it "compares the two pacts" do
+            expect(subject).to include "Pact between Consumer (v3) and Provider"
+            expect(subject).to include "Pact between Consumer (v4) and Provider"
+          end
+
+          it "includes a link to the comparison pact", pending: true do
+            expect(subject).to include "comparision-pact-version:"
+          end
+        end
+
+        context "when there is a previous distinct version" do
           it "indicates when the previous change was made" do
             expect(subject).to include "The following changes were made less than a minute ago (a date)"
           end
@@ -66,7 +94,6 @@ module Pacts
           end
         end
       end
-
     end
   end
 end
diff --git a/spec/lib/pact_broker/pacts/pact_params_spec.rb b/spec/lib/pact_broker/pacts/pact_params_spec.rb
index 87ce56748..c693e4234 100644
--- a/spec/lib/pact_broker/pacts/pact_params_spec.rb
+++ b/spec/lib/pact_broker/pacts/pact_params_spec.rb
@@ -9,19 +9,44 @@ module Pacts
       let(:consumer_version_number) { '1.2.3' }
       let(:headers) { { 'X-Pact-Consumer-Version' => consumer_version_number, 'Host' => 'example.org' } }
       let(:revision_number) { '1' }
+      let(:path_info) do
+        {
+          consumer_name: 'Consumer',
+          provider_name: 'Provider',
+          consumer_version_number: '1.2.3',
+          revision_number: revision_number,
+          pact_version_sha: '123'
+        }
+      end
+
+      describe "from_path_info" do
+        subject { PactParams.from_path_info(path_info) }
+
+        it "extracts the consumer name from the path" do
+          expect(subject.consumer_name).to eq "Consumer"
+        end
+
+        it "extracts the provider name from the path" do
+          expect(subject.provider_name).to eq "Provider"
+        end
+
+        it "extracts the consumer_version_number from the path" do
+          expect(subject.consumer_version_number).to eq "1.2.3"
+        end
+
+        it "extracts the revision_number from the path" do
+          expect(subject.revision_number).to eq "1"
+        end
+
+        it "extracts the pact_version_sha from the path" do
+          expect(subject.pact_version_sha).to eq "123"
+        end
+      end
 
       describe "from_request" do
 
         context "from a PUT request" do
           let(:request) { Webmachine::Request.new("PUT", "/", headers, body)}
-          let(:path_info) do
-            {
-              consumer_name: 'Consumer',
-              provider_name: 'Provider',
-              consumer_version_number: '1.2.3',
-              revision_number: revision_number
-            }
-          end
 
           subject { PactParams.from_request(request, path_info) }
 
diff --git a/spec/lib/pact_broker/pacts/sort_verifiable_content_spec.rb b/spec/lib/pact_broker/pacts/sort_verifiable_content_spec.rb
new file mode 100644
index 000000000..459e916d1
--- /dev/null
+++ b/spec/lib/pact_broker/pacts/sort_verifiable_content_spec.rb
@@ -0,0 +1,25 @@
+require 'pact_broker/pacts/sort_verifiable_content'
+
+module PactBroker
+  module Pacts
+    describe SortVerifiableContent do
+      let(:pact_content_1) do
+        {
+          a: 1,
+          interactions: [{ a: 1, b: 2 }, { a: 2, b: 3 }]
+        }.to_json
+      end
+
+      let(:pact_content_2) do
+        {
+          interactions: [{ b: 3, a: 2}, { b: 2, a: 1 }],
+          a: 1
+        }.to_json
+      end
+
+      it "sorts the interactions/messages and keys in a deterministic way" do
+        expect(SortVerifiableContent.call(pact_content_1).to_json).to eq(SortVerifiableContent.call(pact_content_2).to_json)
+      end
+    end
+  end
+end