diff --git a/app/assets/javascripts/diffs/components/app.vue b/app/assets/javascripts/diffs/components/app.vue
index 02307150e2f52c1c4a4b90c873fbfe15a8429d9e..f644c69f0a032d027fd501f3abaa07a71d3c10c5 100644
--- a/app/assets/javascripts/diffs/components/app.vue
+++ b/app/assets/javascripts/diffs/components/app.vue
@@ -325,7 +325,7 @@ export default {
       this.adjustView();
     },
     viewDiffsFileByFile(newViewFileByFile) {
-      if (!newViewFileByFile && this.diffsIncomplete && this.glFeatures.singleFileFileByFile) {
+      if (!newViewFileByFile && this.diffsIncomplete) {
         this.refetchDiffData({ refetchMeta: false });
       }
     },
@@ -467,26 +467,19 @@ export default {
     subscribeToEvents() {
       notesEventHub.$once('fetchDiffData', this.fetchData);
       notesEventHub.$on('refetchDiffData', this.refetchDiffData);
-      if (this.glFeatures.singleFileFileByFile) {
-        diffsEventHub.$on('diffFilesModified', this.setDiscussions);
-        notesEventHub.$on('fetchedNotesData', this.rereadNoteHash);
-      }
+      notesEventHub.$on('fetchedNotesData', this.rereadNoteHash);
+      diffsEventHub.$on('diffFilesModified', this.setDiscussions);
       diffsEventHub.$on(EVT_MR_PREPARED, this.fetchData);
     },
     unsubscribeFromEvents() {
       diffsEventHub.$off(EVT_MR_PREPARED, this.fetchData);
-      if (this.glFeatures.singleFileFileByFile) {
-        notesEventHub.$off('fetchedNotesData', this.rereadNoteHash);
-        diffsEventHub.$off('diffFilesModified', this.setDiscussions);
-      }
+      diffsEventHub.$off('diffFilesModified', this.setDiscussions);
+      notesEventHub.$off('fetchedNotesData', this.rereadNoteHash);
       notesEventHub.$off('refetchDiffData', this.refetchDiffData);
       notesEventHub.$off('fetchDiffData', this.fetchData);
     },
     navigateToDiffFileNumber(number) {
-      this.navigateToDiffFileIndex({
-        index: number - 1,
-        singleFile: this.glFeatures.singleFileFileByFile,
-      });
+      this.navigateToDiffFileIndex(number - 1);
     },
     refetchDiffData({ refetchMeta = true } = {}) {
       this.fetchData({ toggleTree: false, fetchMeta: refetchMeta });
@@ -506,7 +499,7 @@ export default {
             if (data) {
               realSize = data.real_size;
 
-              if (this.viewDiffsFileByFile && this.glFeatures.singleFileFileByFile) {
+              if (this.viewDiffsFileByFile) {
                 this.fetchFileByFile();
               }
             }
@@ -527,7 +520,7 @@ export default {
           });
       }
 
-      if (!this.viewDiffsFileByFile || !this.glFeatures.singleFileFileByFile) {
+      if (!this.viewDiffsFileByFile) {
         this.fetchDiffFilesBatch()
           .then(() => {
             if (toggleTree) this.setTreeDisplay();
@@ -618,10 +611,7 @@ export default {
     jumpToFile(step) {
       const targetIndex = this.currentDiffIndex + step;
       if (targetIndex >= 0 && targetIndex < this.flatBlobsList.length) {
-        this.goToFile({
-          path: this.flatBlobsList[targetIndex].path,
-          singleFile: this.glFeatures.singleFileFileByFile,
-        });
+        this.goToFile({ path: this.flatBlobsList[targetIndex].path });
       }
     },
     setTreeDisplay() {
diff --git a/app/assets/javascripts/diffs/components/diff_file.vue b/app/assets/javascripts/diffs/components/diff_file.vue
index 4c2cb83ffb3f510f4971e9ccbdd10472d676b2bb..64a7c047cb41092926fe844accfd475d38375d96 100644
--- a/app/assets/javascripts/diffs/components/diff_file.vue
+++ b/app/assets/javascripts/diffs/components/diff_file.vue
@@ -209,12 +209,6 @@ export default {
 
     if (this.hasDiff) {
       this.postRender();
-    } else if (
-      this.viewDiffsFileByFile &&
-      !this.isCollapsed &&
-      !this.glFeatures.singleFileFileByFile
-    ) {
-      this.requestDiff();
     }
 
     this.manageViewedEffects();
diff --git a/app/assets/javascripts/diffs/components/tree_list.vue b/app/assets/javascripts/diffs/components/tree_list.vue
index 4f1875e91751fa6c7696b87897f8070aac17cb42..544bbbfe9d8a503a2a9d965f5fcf4a5c933f2f09 100644
--- a/app/assets/javascripts/diffs/components/tree_list.vue
+++ b/app/assets/javascripts/diffs/components/tree_list.vue
@@ -5,7 +5,6 @@ import micromatch from 'micromatch';
 import { debounce } from 'lodash';
 import { getModifierKey } from '~/constants';
 import { s__, sprintf } from '~/locale';
-import glFeatureFlagsMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
 import { RecycleScroller } from 'vendor/vue-virtual-scroller';
 import DiffFileRow from './diff_file_row.vue';
 
@@ -20,7 +19,6 @@ export default {
     DiffFileRow,
     RecycleScroller,
   },
-  mixins: [glFeatureFlagsMixin()],
   props: {
     hideFileStats: {
       type: Boolean,
@@ -177,7 +175,7 @@ export default {
             :class="{ 'tree-list-parent': item.level > 0 }"
             class="gl-relative"
             @toggleTreeOpen="toggleTreeOpen"
-            @clickFile="(path) => goToFile({ singleFile: glFeatures.singleFileFileByFile, path })"
+            @clickFile="(path) => goToFile({ path })"
           />
         </template>
         <template #after>
diff --git a/app/assets/javascripts/diffs/store/actions.js b/app/assets/javascripts/diffs/store/actions.js
index 3be6562f5863d9ff2e93c62f7cfc0e6baa3d4794..30c34e9a5be4bfe23de360644b50726c629a07dd 100644
--- a/app/assets/javascripts/diffs/store/actions.js
+++ b/app/assets/javascripts/diffs/store/actions.js
@@ -608,8 +608,8 @@ export const setCurrentFileHash = ({ commit }, hash) => {
   commit(types.SET_CURRENT_DIFF_FILE, hash);
 };
 
-export const goToFile = ({ state, commit, dispatch, getters }, { path, singleFile }) => {
-  if (!state.viewDiffsFileByFile || !singleFile) {
+export const goToFile = ({ state, commit, dispatch, getters }, { path }) => {
+  if (!state.viewDiffsFileByFile) {
     dispatch('scrollToFile', { path });
   } else {
     if (!state.treeEntries[path]) return;
@@ -943,16 +943,13 @@ export const setCurrentDiffFileIdFromNote = ({ commit, getters, rootGetters }, n
   }
 };
 
-export const navigateToDiffFileIndex = (
-  { state, getters, commit, dispatch },
-  { index, singleFile },
-) => {
+export const navigateToDiffFileIndex = ({ state, getters, commit, dispatch }, index) => {
   const { fileHash } = getters.flatBlobsList[index];
   document.location.hash = fileHash;
 
   commit(types.SET_CURRENT_DIFF_FILE, fileHash);
 
-  if (state.viewDiffsFileByFile && singleFile) {
+  if (state.viewDiffsFileByFile) {
     dispatch('fetchFileByFile');
   }
 };
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index 91788444f1f6c573f21fa279840449d16e5da4f1..4423929e48b7c8c6c1fdd4d0b064cd92e90de441 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -44,7 +44,6 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
     push_frontend_feature_flag(:refactor_security_extension, @project)
     push_frontend_feature_flag(:deprecate_vulnerabilities_feedback, @project)
     push_frontend_feature_flag(:moved_mr_sidebar, project)
-    push_frontend_feature_flag(:single_file_file_by_file, project)
     push_frontend_feature_flag(:mr_experience_survey, project)
     push_frontend_feature_flag(:realtime_mr_status_change, project)
     push_frontend_feature_flag(:realtime_approvals, project)
diff --git a/app/views/projects/merge_requests/_page.html.haml b/app/views/projects/merge_requests/_page.html.haml
index 3e56148f7777729fc72c7285aeb9118f29dd3b1f..5ea67376a866a0467dd57300b9cb43e718e1110a 100644
--- a/app/views/projects/merge_requests/_page.html.haml
+++ b/app/views/projects/merge_requests/_page.html.haml
@@ -16,7 +16,7 @@
 - add_page_specific_style 'page_bundles/ci_status'
 
 - add_page_startup_api_call @endpoint_metadata_url
-- if mr_action == 'diffs' && (!@file_by_file_default || !single_file_file_by_file?)
+- if mr_action == 'diffs' && !@file_by_file_default
   - add_page_startup_api_call @endpoint_diff_batch_url
 
 .merge-request{ data: { mr_action: mr_action, url: merge_request_path(@merge_request, format: :json), project_path: project_path(@merge_request.project), lock_version: @merge_request.lock_version, diffs_batch_cache_key: @diffs_batch_cache_key } }
diff --git a/spec/frontend/diffs/components/app_spec.js b/spec/frontend/diffs/components/app_spec.js
index 42eec0af961a83e034da7b91055dbaee2497e2a3..29ade6514beed5a5a7fe5c03abe0c0b64145c353 100644
--- a/spec/frontend/diffs/components/app_spec.js
+++ b/spec/frontend/diffs/components/app_spec.js
@@ -711,27 +711,19 @@ describe('diffs/components/app', () => {
       });
 
       it.each`
-        currentDiffFileId | targetFile | newFileByFile
-        ${'123'}          | ${2}       | ${false}
-        ${'312'}          | ${1}       | ${true}
+        currentDiffFileId | targetFile
+        ${'123'}          | ${2}
+        ${'312'}          | ${1}
       `(
         'calls navigateToDiffFileIndex with $index when $link is clicked',
-        async ({ currentDiffFileId, targetFile, newFileByFile }) => {
-          createComponent(
-            { fileByFileUserPreference: true },
-            ({ state }) => {
-              state.diffs.treeEntries = {
-                123: { type: 'blob', fileHash: '123', filePaths: { old: '1234', new: '123' } },
-                312: { type: 'blob', fileHash: '312', filePaths: { old: '3124', new: '312' } },
-              };
-              state.diffs.currentDiffFileId = currentDiffFileId;
-            },
-            {
-              glFeatures: {
-                singleFileFileByFile: newFileByFile,
-              },
-            },
-          );
+        async ({ currentDiffFileId, targetFile }) => {
+          createComponent({ fileByFileUserPreference: true }, ({ state }) => {
+            state.diffs.treeEntries = {
+              123: { type: 'blob', fileHash: '123', filePaths: { old: '1234', new: '123' } },
+              312: { type: 'blob', fileHash: '312', filePaths: { old: '3124', new: '312' } },
+            };
+            state.diffs.currentDiffFileId = currentDiffFileId;
+          });
 
           await nextTick();
 
@@ -741,10 +733,7 @@ describe('diffs/components/app', () => {
 
           await nextTick();
 
-          expect(wrapper.vm.navigateToDiffFileIndex).toHaveBeenCalledWith({
-            index: targetFile - 1,
-            singleFile: newFileByFile,
-          });
+          expect(wrapper.vm.navigateToDiffFileIndex).toHaveBeenCalledWith(targetFile - 1);
         },
       );
     });
diff --git a/spec/frontend/diffs/store/actions_spec.js b/spec/frontend/diffs/store/actions_spec.js
index f084458b5c77681d26b3be3c60698f85f3061e82..d32c2d4665dcc70866d7af3bd78aba6ff9bf6618 100644
--- a/spec/frontend/diffs/store/actions_spec.js
+++ b/spec/frontend/diffs/store/actions_spec.js
@@ -1117,67 +1117,50 @@ describe('DiffsStoreActions', () => {
     });
 
     describe('when the app is in fileByFile mode', () => {
-      describe('when the singleFileFileByFile feature flag is enabled', () => {
-        it('commits SET_CURRENT_DIFF_FILE', () => {
-          diffActions.goToFile(
-            { state, commit, dispatch, getters },
-            { path: file.path, singleFile: true },
-          );
+      it('commits SET_CURRENT_DIFF_FILE', () => {
+        diffActions.goToFile({ state, commit, dispatch, getters }, file);
 
-          expect(commit).toHaveBeenCalledWith(types.SET_CURRENT_DIFF_FILE, fileHash);
-        });
+        expect(commit).toHaveBeenCalledWith(types.SET_CURRENT_DIFF_FILE, fileHash);
+      });
 
-        it('does nothing more if the path has already been loaded', () => {
-          getters.isTreePathLoaded = () => true;
+      it('does nothing more if the path has already been loaded', () => {
+        getters.isTreePathLoaded = () => true;
 
-          diffActions.goToFile(
-            { state, dispatch, getters, commit },
-            { path: file.path, singleFile: true },
-          );
+        diffActions.goToFile({ state, dispatch, getters, commit }, file);
 
-          expect(commit).toHaveBeenCalledWith(types.SET_CURRENT_DIFF_FILE, fileHash);
-          expect(dispatch).toHaveBeenCalledTimes(0);
-        });
+        expect(commit).toHaveBeenCalledWith(types.SET_CURRENT_DIFF_FILE, fileHash);
+        expect(dispatch).toHaveBeenCalledTimes(0);
+      });
 
-        describe('when the tree entry has not been loaded', () => {
-          it('updates location hash', () => {
-            diffActions.goToFile(
-              { state, commit, getters, dispatch },
-              { path: file.path, singleFile: true },
-            );
+      describe('when the tree entry has not been loaded', () => {
+        it('updates location hash', () => {
+          diffActions.goToFile({ state, commit, getters, dispatch }, file);
 
-            expect(document.location.hash).toBe('#test');
-          });
+          expect(document.location.hash).toBe('#test');
+        });
 
-          it('loads the file and then scrolls to it', async () => {
-            diffActions.goToFile(
-              { state, commit, getters, dispatch },
-              { path: file.path, singleFile: true },
-            );
+        it('loads the file and then scrolls to it', async () => {
+          diffActions.goToFile({ state, commit, getters, dispatch }, file);
 
-            // Wait for the fetchFileByFile dispatch to return, to trigger scrollToFile
-            await waitForPromises();
+          // Wait for the fetchFileByFile dispatch to return, to trigger scrollToFile
+          await waitForPromises();
 
-            expect(dispatch).toHaveBeenCalledWith('fetchFileByFile');
-            expect(dispatch).toHaveBeenCalledWith('scrollToFile', file);
-            expect(dispatch).toHaveBeenCalledTimes(2);
-          });
+          expect(dispatch).toHaveBeenCalledWith('fetchFileByFile');
+          expect(dispatch).toHaveBeenCalledWith('scrollToFile', file);
+          expect(dispatch).toHaveBeenCalledTimes(2);
+        });
 
-          it('shows an alert when there was an error fetching the file', async () => {
-            dispatch = jest.fn().mockRejectedValue();
+        it('shows an alert when there was an error fetching the file', async () => {
+          dispatch = jest.fn().mockRejectedValue();
 
-            diffActions.goToFile(
-              { state, commit, getters, dispatch },
-              { path: file.path, singleFile: true },
-            );
+          diffActions.goToFile({ state, commit, getters, dispatch }, file);
 
-            // Wait for the fetchFileByFile dispatch to return, to trigger the catch
-            await waitForPromises();
+          // Wait for the fetchFileByFile dispatch to return, to trigger the catch
+          await waitForPromises();
 
-            expect(createAlert).toHaveBeenCalledTimes(1);
-            expect(createAlert).toHaveBeenCalledWith({
-              message: expect.stringMatching(LOAD_SINGLE_DIFF_FAILED),
-            });
+          expect(createAlert).toHaveBeenCalledTimes(1);
+          expect(createAlert).toHaveBeenCalledWith({
+            message: expect.stringMatching(LOAD_SINGLE_DIFF_FAILED),
           });
         });
       });
@@ -1798,17 +1781,17 @@ describe('DiffsStoreActions', () => {
     it('commits SET_CURRENT_DIFF_FILE', () => {
       return testAction(
         diffActions.navigateToDiffFileIndex,
-        { index: 0, singleFile: false },
+        0,
         { flatBlobsList: [{ fileHash: '123' }] },
         [{ type: types.SET_CURRENT_DIFF_FILE, payload: '123' }],
         [],
       );
     });
 
-    it('dispatches the fetchFileByFile action when the state value viewDiffsFileByFile is true and the single-file file-by-file feature flag is enabled', () => {
+    it('dispatches the fetchFileByFile action when the state value viewDiffsFileByFile is true', () => {
       return testAction(
         diffActions.navigateToDiffFileIndex,
-        { index: 0, singleFile: true },
+        0,
         { viewDiffsFileByFile: true, flatBlobsList: [{ fileHash: '123' }] },
         [{ type: types.SET_CURRENT_DIFF_FILE, payload: '123' }],
         [{ type: 'fetchFileByFile' }],