diff --git a/configs/main.js.example b/configs/main.js.example
index 0f38a51c..1c3b3be5 100644
--- a/configs/main.js.example
+++ b/configs/main.js.example
@@ -290,6 +290,7 @@ module.exports = {
 		codeTheme: 'ir-black',
 		sfw: false, //safe for work board
 		lockMode: 0, //board lock mode
+		fileR9KMode: 0, //r9k for files, 0=off, 1=per thread, 2=whole board
 		unlistedLocal: false, //board hidden from on-site board list and frontpage
 		unlistedWebring: false, //board hidden from webring
 		captchaMode: 0, //0=disabled, 1=for threads, 2=for all posts
diff --git a/db/posts.js b/db/posts.js
index e370f890..3681f8a8 100644
--- a/db/posts.js
+++ b/db/posts.js
@@ -296,6 +296,27 @@ module.exports = {
 
 	},
 
+	checkExistingFiles: async (board, thread = null, hashes) => {
+		const query = {
+			'board': board,
+			'files.hash': {
+				'$in': hashes
+			}
+		}
+		if (thread !== null) {
+			query['$or'] = [
+				{ 'thread': thread },
+				{ 'postId': thread },
+			]
+		}
+		const postWithExistingFiles = await db.findOne(query, {
+			'projection': {
+				'files.hash': 1,
+			}
+		});
+		return postWithExistingFiles;
+	},
+
 	allBoardPosts: (board) => {
 		return db.find({
 			'board': board
diff --git a/helpers/paramconverter.js b/helpers/paramconverter.js
index e0b1f809..b8b56ae6 100644
--- a/helpers/paramconverter.js
+++ b/helpers/paramconverter.js
@@ -5,7 +5,7 @@ const { ObjectId } = require(__dirname+'/../db/db.js')
 		'checkedreports', 'checkedbans', 'checkedbanners', 'checkedaccounts', 'countries']) //only these should be arrays, since express bodyparser can output arrays
 	, trimFields = ['tags', 'uri', 'moderators', 'filters', 'announcement', 'description', 'message',
 		'name', 'subject', 'email', 'postpassword', 'password', 'default_name', 'report_reason', 'ban_reason', 'log_message', 'custom_css'] //trim if we dont want filed with whitespace
-	, numberFields = ['filter_mode', 'lock_mode', 'captcha_mode', 'tph_trigger', 'pph_trigger', 'trigger_action', 'bump_limit', 'reply_limit', 'move_to_thread',, 'postId',
+	, numberFields = ['filter_mode', 'lock_mode', 'file_r9k_mode', 'captcha_mode', 'tph_trigger', 'pph_trigger', 'trigger_action', 'bump_limit', 'reply_limit', 'move_to_thread',, 'postId',
 		'max_files', 'thread_limit', 'thread', 'max_thread_message_length', 'max_reply_message_length', 'min_thread_message_length', 'min_reply_message_length', 'auth_level'] //convert these to numbers before they hit our routes
 	, banDurationRegex = /^(?<YEAR>[\d]+y)?(?<MONTH>[\d]+m)?(?<WEEK>[\d]+w)?(?<DAY>[\d]+d)?(?<HOUR>[\d]+h)?$/
 	, timeUtils = require(__dirname+'/timeutils.js')
diff --git a/migrations/index.js b/migrations/index.js
index 6dbd6a62..6cdd6bfe 100644
--- a/migrations/index.js
+++ b/migrations/index.js
@@ -13,4 +13,5 @@ module.exports = {
 	'0.0.10': require(__dirname+'/migration-0.0.10.js'), //add links to modlog for new logs
 	'0.0.11': require(__dirname+'/migration-0.0.11.js'), //rename captcha "text" field to "answer" since we support multiple captcha types now
 	'0.0.12': require(__dirname+'/migration-0.0.12.js'), //yotsuba b -> yotsuba-b
+	'0.0.13': require(__dirname+'/migration-0.0.13.js'), //add r9k mode
 }
diff --git a/migrations/migration-0.0.13.js b/migrations/migration-0.0.13.js
new file mode 100644
index 00000000..82dc45b9
--- /dev/null
+++ b/migrations/migration-0.0.13.js
@@ -0,0 +1,12 @@
+'use strict';
+
+module.exports = async(db, redis) => {
+	console.log('Adding file r9k setting to boards db');
+	await db.collection('boards').updateMany({}, {
+		'$set': {
+			'settings.fileR9KMode': 0,
+		}
+	});
+	console.log('Cleared boards cache');
+	await redis.deletePattern('board:*');
+};
diff --git a/models/forms/changeboardsettings.js b/models/forms/changeboardsettings.js
index 5761c39c..3377ed95 100644
--- a/models/forms/changeboardsettings.js
+++ b/models/forms/changeboardsettings.js
@@ -107,6 +107,7 @@ module.exports = async (req, res, next) => {
 		'maxThreadMessageLength': numberSetting(req.body.max_thread_message_length, oldSettings.maxThreadMessageLength),
 		'maxReplyMessageLength': numberSetting(req.body.max_reply_message_length, oldSettings.maxReplyMessageLength),
 		'lockMode': numberSetting(req.body.lock_mode, oldSettings.lockMode),
+		'fileR9KMode': numberSetting(req.body.file_r9k_mode, oldSettings.fileR9KMode),
 		'filterMode': numberSetting(req.body.filter_mode, oldSettings.filterMode),
 		'filterBanDuration': numberSetting(req.body.ban_duration, oldSettings.filterBanDuration),
 		'tags': arraySetting(req.body.tags, oldSettings.tags, 10),
diff --git a/models/forms/makepost.js b/models/forms/makepost.js
index 3541d516..272e4eac 100644
--- a/models/forms/makepost.js
+++ b/models/forms/makepost.js
@@ -50,7 +50,7 @@ module.exports = async (req, res, next) => {
 	const { filterBanDuration, filterMode, filters, blockedCountries, resetTrigger,
 			maxFiles, sageOnlyEmail, forceAnon, replyLimit, disableReplySubject,
 			threadLimit, ids, userPostSpoiler, pphTrigger, tphTrigger, triggerAction,
-			captchaMode, lockMode, allowedFileTypes, flags } = res.locals.board.settings;
+			captchaMode, lockMode, allowedFileTypes, flags, fileR9KMode } = res.locals.board.settings;
 	if (res.locals.permLevel >= 4
 		&& res.locals.country
 		&& blockedCountries.includes(res.locals.country.code)) {
@@ -161,6 +161,22 @@ module.exports = async (req, res, next) => {
 	let files = [];
 	// if we got a file
 	if (res.locals.numFiles > 0) {
+		if ((req.body.thread && fileR9KMode === 1) || fileR9KMode === 2) {
+			const filesHashes = req.files.file.map(f => f.sha256);
+			const postWithExistingFiles = await Posts.checkExistingFiles(res.locals.board._id, (fileR9KMode === 2 ? null : req.body.thread), filesHashes);
+			if (postWithExistingFiles != null) {
+				await deleteTempFiles(req).catch(e => console.error);
+				const conflictingFiles = req.files.file
+					.filter(f => postWithExistingFiles.files.some(fx => fx.hash === f.sha256))
+					.map(f => f.name)
+					.join(', ');
+				return dynamicResponse(req, res, 409, 'message', {
+					'title': 'Conflict',
+					'message': `Uploaded files must be unique ${fileR9KMode === 1 ? 'in this thread' : 'on this board'}.\nAt least the following file${conflictingFiles.length > 1 ? 's are': ' is'} not unique: ${conflictingFiles}`,
+					'redirect': redirect
+				});
+			}
+		}
 		// check all mime types before we try saving anything
 		for (let i = 0; i < res.locals.numFiles; i++) {
 			if (!mimeTypes.allowed(req.files.file[i].mimetype, allowedFileTypes)) {
diff --git a/package.json b/package.json
index 6809e3f2..d1fc9863 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "jschan",
   "version": "0.0.1",
-  "migrateVersion": "0.0.12",
+  "migrateVersion": "0.0.13",
   "description": "",
   "main": "server.js",
   "dependencies": {
diff --git a/views/pages/managesettings.pug b/views/pages/managesettings.pug
index 60557fd0..31b27625 100644
--- a/views/pages/managesettings.pug
+++ b/views/pages/managesettings.pug
@@ -161,6 +161,12 @@ block content
 							option(value='0', selected=board.settings.lockMode === 0) Unlocked
 							option(value='1', selected=board.settings.lockMode === 1) Lock thread creation
 							option(value='2', selected=board.settings.lockMode === 2) Lock board
+					.row
+						.label Unique Files
+						select(name='file_r9k_mode')
+							option(value='0', selected=board.settings.fileR9KMode === 0) Off
+							option(value='1', selected=board.settings.fileR9KMode === 1) Per Thread
+							option(value='2', selected=board.settings.fileR9KMode === 2) Board Wide
 					.row
 						.label Unlist locally
 						label.postform-style.ph-5