diff --git a/public/openapi/components/schemas/PostObject.yaml b/public/openapi/components/schemas/PostObject.yaml
index f02b8a5b9c..7b8341f03c 100644
--- a/public/openapi/components/schemas/PostObject.yaml
+++ b/public/openapi/components/schemas/PostObject.yaml
@@ -34,6 +34,9 @@ PostObject:
     sourceContent:
       type: string
       nullable: true
+    anonymous:
+      type: number
+      description: Whether this post was made anonymously (1 for anonymous, 0 for not)
     uid:
       type: number
       description: A user identifier
@@ -203,6 +206,9 @@ PostDataObject:
           type: string
         timestamp:
           type: number
+        anonymous:
+          type: number
+          description: Whether this post was made anonymously (1 for anonymous, 0 for not)
         votes:
           type: number
         deleted:
diff --git a/public/openapi/read/topic/topic_id.yaml b/public/openapi/read/topic/topic_id.yaml
index 81b3e9531f..f4e4f8d8c9 100644
--- a/public/openapi/read/topic/topic_id.yaml
+++ b/public/openapi/read/topic/topic_id.yaml
@@ -150,6 +150,8 @@ get:
                         type: boolean
                       isAdminOrMod:
                         type: boolean
+                      isAdmin:
+                        type: boolean
                       disabled:
                         type: number
                       tid:
diff --git a/src/api/posts.js b/src/api/posts.js
index 7c892dec97..e2dff69047 100644
--- a/src/api/posts.js
+++ b/src/api/posts.js
@@ -42,6 +42,11 @@ postsAPI.get = async function (caller, data) {
 		post.content = '[[topic:post-is-deleted]]';
 	}
 
+	if (post.anonymous === 1) {
+		const isAdmin = await user.isAdministrator(caller.uid);
+		posts.anonymizePost(post, isAdmin);
+	}
+
 	return post;
 };
 
@@ -571,7 +576,11 @@ postsAPI.getReplies = async (caller, { pid }) => {
 		privileges.posts.get(pids, uid),
 	]);
 	postData = await topics.addPostData(postData, uid);
-	postData.forEach((postData, index) => posts.modifyPostByPrivilege(postData, postPrivileges[index]));
+	const isAdmin = await user.isAdministrator(uid);
+	postData.forEach((postData, index) => {
+		posts.modifyPostByPrivilege(postData, postPrivileges[index]);
+		posts.anonymizePost(postData, isAdmin);
+	});
 	postData = postData.filter((postData, index) => postData && postPrivileges[index].read);
 	postData = await user.blocks.filter(uid, postData);
 
diff --git a/src/posts/create.js b/src/posts/create.js
index 044b07d699..48cbc10708 100644
--- a/src/posts/create.js
+++ b/src/posts/create.js
@@ -39,6 +39,7 @@ module.exports = function (Posts) {
 		if (data.handle && !parseInt(uid, 10)) {
 			postData.handle = data.handle;
 		}
+		postData.anonymous = data.anonymous ? 1 : 0;
 		if (_activitypub) {
 			if (_activitypub.url) {
 				postData.url = _activitypub.url;
diff --git a/src/posts/data.js b/src/posts/data.js
index 57bd089f91..28d280e752 100644
--- a/src/posts/data.js
+++ b/src/posts/data.js
@@ -6,7 +6,7 @@ const utils = require('../utils');
 const intFields = [
 	'uid', 'pid', 'tid', 'deleted', 'timestamp',
 	'upvotes', 'downvotes', 'deleterUid', 'edited',
-	'replies', 'bookmarks', 'announces',
+	'replies', 'bookmarks', 'announces', 'anonymous',
 ];
 const groups = require('../groups');
 const user = require('../user');
diff --git a/src/posts/index.js b/src/posts/index.js
index 59c61381b9..de6123e739 100644
--- a/src/posts/index.js
+++ b/src/posts/index.js
@@ -95,6 +95,27 @@ Posts.getPostIndices = async function (posts, uid) {
 	return indices.map(index => (utils.isNumber(index) ? parseInt(index, 10) + 1 : 0));
 };
 
+Posts.anonymizePost = function (post, isAdmin) {
+	if (post && post.anonymous === 1 && !isAdmin) {
+		post.uid = 0;
+		post.user = {
+			uid: 0,
+			username: 'Anonymous',
+			displayname: 'Anonymous',
+			userslug: '',
+			picture: '',
+			signature: '',
+			status: 'offline',
+			selectedGroups: [],
+			custom_profile_info: [],
+			'icon:text': '?',
+			'icon:bgColor': '#aaa',
+		};
+		post.editor = null;
+		post.selfPost = false;
+	}
+};
+
 Posts.modifyPostByPrivilege = function (post, privileges) {
 	if (post && post.deleted && !(post.selfPost || privileges['posts:view_deleted'])) {
 		post.content = '[[topic:post-is-deleted]]';
diff --git a/src/posts/summary.js b/src/posts/summary.js
index 5995514eb6..836233bdda 100644
--- a/src/posts/summary.js
+++ b/src/posts/summary.js
@@ -10,6 +10,7 @@ const user = require('../user');
 const plugins = require('../plugins');
 const categories = require('../categories');
 const utils = require('../utils');
+const privileges = require('../privileges');
 
 module.exports = function (Posts) {
 	Posts.getPostSummaryByPids = async function (pids, uid, options) {
@@ -22,7 +23,7 @@ module.exports = function (Posts) {
 		options.escape = options.hasOwnProperty('escape') ? options.escape : false;
 		options.extraFields = options.hasOwnProperty('extraFields') ? options.extraFields : [];
 
-		const fields = ['pid', 'tid', 'toPid', 'url', 'content', 'sourceContent', 'uid', 'timestamp', 'deleted', 'upvotes', 'downvotes', 'replies', 'handle'].concat(options.extraFields);
+		const fields = ['pid', 'tid', 'toPid', 'url', 'content', 'sourceContent', 'uid', 'timestamp', 'deleted', 'upvotes', 'downvotes', 'replies', 'handle', 'anonymous'].concat(options.extraFields);
 
 		let posts = await Posts.getPostsFields(pids, fields);
 		posts = posts.filter(Boolean);
@@ -40,6 +41,8 @@ module.exports = function (Posts) {
 		const tidToTopic = toObject('tid', topicsAndCategories.topics);
 		const cidToCategory = toObject('cid', topicsAndCategories.categories);
 
+		const isAdmin = await privileges.users.isAdministrator(uid);
+
 		posts.forEach((post) => {
 			// If the post author isn't represented in the retrieved users' data,
 			// then it means they were deleted, assume guest.
@@ -53,6 +56,8 @@ module.exports = function (Posts) {
 			post.user = uidToUser[post.uid];
 			Posts.overrideGuestHandle(post, post.handle);
 			post.handle = undefined;
+
+			Posts.anonymizePost(post, isAdmin);
 			post.topic = tidToTopic[post.tid];
 			post.category = post.topic && cidToCategory[post.topic.cid];
 			post.isMainPost = post.topic && post.pid === post.topic.mainPid;
diff --git a/src/privileges/topics.js b/src/privileges/topics.js
index 5538e626d9..ef2a8ce3a6 100644
--- a/src/privileges/topics.js
+++ b/src/privileges/topics.js
@@ -64,6 +64,7 @@ privsTopics.get = async function (tid, uid) {
 		view_deleted: isAdminOrMod || isOwner || privData['posts:view_deleted'],
 		view_scheduled: privData['topics:schedule'] || isAdministrator,
 		isAdminOrMod: isAdminOrMod,
+		isAdmin: isAdministrator,
 		disabled: disabled,
 		tid: tid,
 		uid: uid,
diff --git a/src/topics/posts.js b/src/topics/posts.js
index a8535939e9..bb6dd61f84 100644
--- a/src/topics/posts.js
+++ b/src/topics/posts.js
@@ -163,6 +163,9 @@ module.exports = function (Topics) {
 		const loggedIn = parseInt(topicPrivileges.uid, 10) > 0;
 		topicData.posts.forEach((post) => {
 			if (post) {
+				// Anonymize posts with anonymous flag for non-admin viewers
+				posts.anonymizePost(post, topicPrivileges.isAdmin === true);
+
 				post.topicOwnerPost = parseInt(topicData.uid, 10) === parseInt(post.uid, 10);
 				post.display_edit_tools = topicPrivileges.isAdminOrMod || (post.selfPost && topicPrivileges['posts:edit']);
 				post.display_delete_tools = topicPrivileges.isAdminOrMod || (post.selfPost && topicPrivileges['posts:delete']);
diff --git a/test/posts.js b/test/posts.js
index 0e8ad7fc4a..3b9064c4a8 100644
--- a/test/posts.js
+++ b/test/posts.js
@@ -1302,6 +1302,222 @@ describe('Post\'s', () => {
 			});
 		});
 	});
+
+	describe('Anonymous posts', () => {
+		let adminUid;
+		let regularUid;
+		let anonCid;
+		let anonTopicData;
+		let anonPost;
+		let normalPost;
+
+		before(async () => {
+			adminUid = await user.create({ username: 'anon_admin' });
+			await groups.join('administrators', adminUid);
+			regularUid = await user.create({ username: 'anon_regular' });
+			({ cid: anonCid } = await categories.create({
+				name: 'Anon Test Category',
+				description: 'Category for anonymous post tests',
+			}));
+			anonTopicData = await topics.post({
+				uid: regularUid,
+				cid: anonCid,
+				title: 'Anonymous Test Topic',
+				content: 'Topic for anonymous post tests',
+			});
+			anonPost = await topics.reply({
+				uid: regularUid,
+				tid: anonTopicData.topicData.tid,
+				content: 'anon reply',
+				anonymous: true,
+			});
+			normalPost = await topics.reply({
+				uid: regularUid,
+				tid: anonTopicData.topicData.tid,
+				content: 'normal reply',
+				anonymous: false,
+			});
+		});
+
+		describe('Anonymous flag storage', () => {
+			it('should store anonymous flag as 1 when anonymous is true', async () => {
+				const value = await posts.getPostField(anonPost.pid, 'anonymous');
+				assert.strictEqual(value, 1);
+			});
+
+			it('should store anonymous flag as 0 when anonymous is falsy', async () => {
+				const value = await posts.getPostField(normalPost.pid, 'anonymous');
+				assert.strictEqual(value, 0);
+			});
+		});
+
+		describe('API masking for regular users', () => {
+			it('should mask poster identity for regular users on anonymous posts', async () => {
+				const post = await apiPosts.get({ uid: regularUid }, { pid: anonPost.pid });
+				assert.strictEqual(post.uid, 0);
+				assert.strictEqual(post.user.username, 'Anonymous');
+				assert.strictEqual(post.user.displayname, 'Anonymous');
+				assert.strictEqual(post.user['icon:text'], '?');
+			});
+
+			it('should not have isAnonymous flag for regular users', async () => {
+				const post = await apiPosts.get({ uid: regularUid }, { pid: anonPost.pid });
+				assert.strictEqual(post.isAnonymous, undefined);
+			});
+		});
+
+		describe('Admin visibility', () => {
+			it('should expose real user data and preserve anonymous flag for admins', async () => {
+				const post = await apiPosts.get({ uid: adminUid }, { pid: anonPost.pid });
+				assert.strictEqual(post.anonymous, 1);
+				assert.strictEqual(post.uid, regularUid);
+			});
+		});
+
+		describe('Regression for non-anonymous posts', () => {
+			it('should not mask poster on non-anonymous posts for regular users', async () => {
+				const post = await apiPosts.get({ uid: regularUid }, { pid: normalPost.pid });
+				assert.strictEqual(post.uid, regularUid);
+				assert.strictEqual(post.isAnonymous, undefined);
+				assert(!post.user || post.user.uid !== 0, 'non-anonymous post should not have masked user');
+			});
+		});
+
+		describe('Topic-level masking (modifyPostsByPrivilege)', () => {
+			it('should mask anonymous posts in topic view for regular users', () => {
+				const mockTopicData = {
+					uid: regularUid,
+					locked: false,
+					postSharing: [],
+					posts: [
+						{
+							anonymous: 1,
+							uid: regularUid,
+							user: { uid: regularUid, username: 'anon_regular', displayname: 'anon_regular' },
+							editor: { uid: regularUid },
+							selfPost: true,
+							deleted: false,
+							index: 1,
+						},
+						{
+							anonymous: 0,
+							uid: regularUid,
+							user: { uid: regularUid, username: 'anon_regular', displayname: 'anon_regular' },
+							editor: null,
+							selfPost: true,
+							deleted: false,
+							index: 2,
+						},
+					],
+				};
+				topics.modifyPostsByPrivilege(mockTopicData, {
+					uid: regularUid,
+					isAdmin: false,
+					isAdminOrMod: false,
+					'posts:edit': false,
+					'posts:delete': false,
+				});
+				const anonPostResult = mockTopicData.posts[0];
+				assert.strictEqual(anonPostResult.user.username, 'Anonymous');
+				assert.strictEqual(anonPostResult.editor, null);
+				assert.strictEqual(anonPostResult.selfPost, false);
+			});
+
+			it('should not set isAnonymous flag (removed)', () => {
+				const mockTopicData = {
+					uid: regularUid,
+					locked: false,
+					postSharing: [],
+					posts: [
+						{
+							anonymous: 1,
+							uid: regularUid,
+							user: { uid: regularUid, username: 'anon_regular', displayname: 'anon_regular' },
+							editor: null,
+							selfPost: false,
+							deleted: false,
+							index: 1,
+						},
+					],
+				};
+				topics.modifyPostsByPrivilege(mockTopicData, {
+					uid: adminUid,
+					isAdmin: true,
+					isAdminOrMod: true,
+					'posts:edit': true,
+					'posts:delete': true,
+				});
+				assert.strictEqual(mockTopicData.posts[0].isAnonymous, undefined);
+			});
+
+			it('should preserve real user data on anonymous posts in topic view for admins', () => {
+				const originalUser = { uid: regularUid, username: 'anon_regular', displayname: 'anon_regular' };
+				const mockTopicData = {
+					uid: regularUid,
+					locked: false,
+					postSharing: [],
+					posts: [
+						{
+							anonymous: 1,
+							uid: regularUid,
+							user: { ...originalUser },
+							editor: null,
+							selfPost: false,
+							deleted: false,
+							index: 1,
+						},
+					],
+				};
+				topics.modifyPostsByPrivilege(mockTopicData, {
+					uid: adminUid,
+					isAdmin: true,
+					isAdminOrMod: true,
+					'posts:edit': true,
+					'posts:delete': true,
+				});
+				const anonPostResult = mockTopicData.posts[0];
+				assert.strictEqual(anonPostResult.anonymous, 1);
+				assert.strictEqual(anonPostResult.user.uid, regularUid);
+				assert.strictEqual(anonPostResult.user.username, 'anon_regular');
+			});
+		});
+
+		describe('Replies endpoint masking', () => {
+			let parentPost;
+			let anonReply;
+
+			before(async () => {
+				parentPost = await topics.reply({
+					uid: adminUid,
+					tid: anonTopicData.topicData.tid,
+					content: 'parent post for reply test',
+				});
+				anonReply = await topics.reply({
+					uid: regularUid,
+					tid: anonTopicData.topicData.tid,
+					content: 'anonymous reply to parent',
+					anonymous: true,
+					toPid: parentPost.pid,
+				});
+			});
+
+			it('should mask anonymous replies for regular users via getReplies', async () => {
+				const replies = await apiPosts.getReplies({ uid: regularUid }, { pid: parentPost.pid });
+				const reply = replies.find(r => r.pid === anonReply.pid);
+				assert(reply, 'anonymous reply should be in replies');
+				assert.strictEqual(reply.user.username, 'Anonymous');
+				assert.strictEqual(reply.user.uid, 0);
+			});
+
+			it('should expose real user data on anonymous replies for admins via getReplies', async () => {
+				const replies = await apiPosts.getReplies({ uid: adminUid }, { pid: parentPost.pid });
+				const reply = replies.find(r => r.pid === anonReply.pid);
+				assert(reply, 'anonymous reply should be in replies');
+				assert.strictEqual(reply.anonymous, 1);
+				assert.strictEqual(reply.user.uid, regularUid);
+			});
+		});
+	});
 });
 
 describe('Posts\'', async () => {