diff --git a/TODO b/TODO
index 4a642b97..03f12696 100644
--- a/TODO
+++ b/TODO
@@ -20,8 +20,9 @@ everything related to posts:
           (move post snapshot factory methods to PostService)
 
 everything related to tags:
+    - automatic tag removal
+    - tag refresh when editing post
     - tag listing
-    - tag autocompletion (difficult)
     - time of last tag usage
     - time of tag addition
     - mass tag
diff --git a/public_html/css/tags.css b/public_html/css/tags.css
new file mode 100644
index 00000000..9c522f91
--- /dev/null
+++ b/public_html/css/tags.css
@@ -0,0 +1,23 @@
+.autocomplete {
+	position: absolute;
+	display: none;
+	z-index: 10;
+}
+.autocomplete ul {
+	list-style-type: none;
+	padding: 0 0 !important;
+	margin: 0 !important;
+	border: 2px solid #5da;
+	background: white;
+	display: block !important;
+	text-align: left;
+}
+
+.autocomplete li {
+	margin: 0;
+	padding: 0.1em 0.5em !important;
+}
+
+.autocomplete li.active {
+	background: #5da;
+}
diff --git a/public_html/index.html b/public_html/index.html
index dbef564a..1ca3f8e9 100644
--- a/public_html/index.html
+++ b/public_html/index.html
@@ -37,6 +37,7 @@
 	<link rel="stylesheet" type="text/css" href="/css/home.css"/>
 	<link rel="stylesheet" type="text/css" href="/css/history.css"/>
 	<link rel="stylesheet" type="text/css" href="/css/comments.css"/>
+	<link rel="stylesheet" type="text/css" href="/css/tags.css"/>
 	<!-- /build -->
 
 	<!-- build:remove -->
@@ -86,9 +87,11 @@
 	<script type="text/javascript" src="/js/Pager.js"></script>
 	<script type="text/javascript" src="/js/BrowsingSettings.js"></script>
 	<script type="text/javascript" src="/js/Controls/FileDropper.js"></script>
+	<script type="text/javascript" src="/js/Controls/AutoCompleteInput.js"></script>
 	<script type="text/javascript" src="/js/Controls/TagInput.js"></script>
 	<script type="text/javascript" src="/js/PresenterManager.js"></script>
 
+	<script type="text/javascript" src="/js/Services/TagList.js"></script>
 	<script type="text/javascript" src="/js/Services/PostsAroundCalculator.js"></script>
 
 	<script type="text/javascript" src="/js/Presenters/TopNavigationPresenter.js"></script>
diff --git a/public_html/js/Controls/AutoCompleteInput.js b/public_html/js/Controls/AutoCompleteInput.js
new file mode 100644
index 00000000..26a027da
--- /dev/null
+++ b/public_html/js/Controls/AutoCompleteInput.js
@@ -0,0 +1,223 @@
+var App = App || {};
+App.Controls = App.Controls || {};
+
+App.Controls.AutoCompleteInput = function($input) {
+	var _ = App.DI.get('_');
+	var jQuery = App.DI.get('jQuery');
+	var tagList = App.DI.get('tagList');
+
+	var KEY_RETURN = 13;
+	var KEY_ESCAPE = 27;
+	var KEY_UP = 38;
+	var KEY_DOWN = 40;
+
+	var options = {
+		caseSensitive: false,
+		source: null,
+		maxResults: 15,
+		minLengthToArbitrarySearch: 3,
+		onApply: null,
+		additionalFilter: null,
+	};
+	var showTimeout = null;
+	var cachedSource = null;
+	var results = [];
+	var activeResult = -1;
+
+	if ($input.length === 0) {
+		throw new Error('Input element was not found');
+	}
+	if ($input.length > 1) {
+		throw new Error('Cannot add autocompletion to more than one element at once');
+	}
+	if ($input.attr('data-autocomplete')) {
+		throw new Error('Autocompletion was already added for this element');
+	}
+	$input.attr('data-autocomplete', true);
+	$input.attr('autocomplete', 'off');
+
+	var $div = jQuery('<div>');
+	var $list = jQuery('<ul>');
+	$div.addClass('autocomplete');
+	$div.append($list);
+	jQuery(document.body).append($div);
+
+	function getSource() {
+		if (cachedSource) {
+			return cachedSource;
+		} else {
+			var source = source || tagList.getTags();
+			source = _.pairs(source);
+			source = _.sortBy(source, function(a) { return -a[1]; });
+			source = _.filter(source, function(a) { return a[1] > 0; });
+			source = _.map(source, function(a) { return [a[0], a[0] + ' (' + a[1] + ')']; });
+			cachedSource = source;
+			return source;
+		}
+	}
+
+	$input.bind('keydown', function(e) {
+		if (isShown() && e.which === KEY_ESCAPE) {
+			e.preventDefault();
+			e.stopPropagation();
+			e.stopImmediatePropagation();
+			hide();
+		} else if (isShown() && e.which === KEY_DOWN) {
+			e.preventDefault();
+			e.stopPropagation();
+			e.stopImmediatePropagation();
+			selectNext();
+		} else if (isShown() && e.which === KEY_UP) {
+			e.preventDefault();
+			e.stopPropagation();
+			e.stopImmediatePropagation();
+			selectPrevious();
+		} else if (isShown() && e.which === KEY_RETURN && activeResult >= 0) {
+			e.preventDefault();
+			e.stopPropagation();
+			e.stopImmediatePropagation();
+			applyAutocomplete();
+			hide();
+		} else {
+			window.clearTimeout(showTimeout);
+			showTimeout = window.setTimeout(showOrHide, 250);
+		}
+	});
+
+	$input.blur(function(e) {
+		window.clearTimeout(showTimeout);
+		window.setTimeout(function() { hide(); }, 50);
+	});
+
+	function getSelectionStart(){
+		var input = $input.get(0);
+		if (!input) {
+			return;
+		}
+		if ('selectionStart' in input) {
+			return input.selectionStart;
+		} else if (document.selection) {
+			input.focus();
+			var sel = document.selection.createRange();
+			var selLen = document.selection.createRange().text.length;
+			sel.moveStart('character', -input.value.length);
+			return sel.text.length - selLen;
+		} else {
+			return 0;
+		}
+	}
+
+	function getTextToFind() {
+		var val = $input.val();
+		var start = getSelectionStart();
+		return val.substring(0, start).replace(/.*\s/, '');
+	}
+
+	function showOrHide() {
+		var textToFind = getTextToFind();
+		if (textToFind.length === 0) {
+			hide();
+		} else {
+			updateResults(textToFind);
+			refreshList();
+		}
+	}
+
+	function isShown() {
+		return $div.is(':visible');
+	}
+
+	function hide() {
+		$div.hide();
+	}
+
+	function selectPrevious() {
+		select(activeResult === -1 ? results.length - 1 : activeResult - 1);
+	}
+
+	function selectNext() {
+		select(activeResult === -1 ? 0 : activeResult + 1);
+	}
+
+	function select(newActiveResult) {
+		if (newActiveResult >= 0 && newActiveResult < results.length) {
+			activeResult = newActiveResult;
+			refreshActiveResult();
+		} else {
+			activeResult = - 1;
+			refreshActiveResult();
+		}
+	}
+
+	function getResultsFilter(textToFind) {
+		if (textToFind.length < options.minLengthToArbitrarySearch) {
+			return options.caseSensitive ?
+				function(resultItem) { return resultItem[0].indexOf(textToFind) === 0; } :
+				function(resultItem) { return resultItem[0].toLowerCase().indexOf(textToFind.toLowerCase()) === 0; };
+		} else {
+			return options.caseSensitive ?
+				function(resultItem) { return resultItem[0].indexOf(textToFind) >= 0; } :
+				function(resultItem) { return resultItem[0].toLowerCase().indexOf(textToFind.toLowerCase()) >= 0; };
+		}
+	}
+
+	function updateResults(textToFind) {
+		var source = getSource();
+		var filter = getResultsFilter(textToFind);
+		results = _.filter(source, filter);
+		if (options.additionalFilter) {
+			results = options.additionalFilter(results);
+		}
+		results = results.slice(0, options.maxResults);
+		activeResult = -1;
+	}
+
+	function applyAutocomplete() {
+		if (options.onApply) {
+			options.onApply(results[activeResult][0]);
+		} else {
+			var val = $input.val();
+			var start = getSelectionStart();
+			var prefix = '';
+			var suffix = val.substring(start);
+			var middle = val.substring(0, start);
+			var index = middle.lastIndexOf(' ');
+			if (index !== -1) {
+				prefix = val.substring(0, index + 1);
+				middle = val.substring(index + 1);
+			}
+			$input.val(prefix + results[activeResult][0] + ' ' + suffix.trimLeft());
+			$input.focus();
+		}
+	}
+
+	function refreshList() {
+		if (results.length === 0) {
+			hide();
+			return;
+		}
+
+		$list.empty();
+		_.each(results, function(resultItem) {
+			var $listItem = jQuery('<li/>');
+			$listItem.text(resultItem[1]);
+			$listItem.attr('data-key', resultItem[0]);
+			$list.append($listItem);
+		});
+		refreshActiveResult();
+		$div.css({
+			left: ($input.offset().left) + 'px',
+			top: ($input.offset().top + $input.outerHeight() - 2) + 'px',
+		});
+		$div.show();
+	}
+
+	function refreshActiveResult() {
+		$list.find('li.active').removeClass('active');
+		if (activeResult >= 0) {
+			$list.find('li').eq(activeResult).addClass('active');
+		}
+	}
+
+	return options;
+};
diff --git a/public_html/js/Controls/FileDropper.js b/public_html/js/Controls/FileDropper.js
index 3344023a..007b02b6 100644
--- a/public_html/js/Controls/FileDropper.js
+++ b/public_html/js/Controls/FileDropper.js
@@ -1,10 +1,9 @@
 var App = App || {};
 App.Controls = App.Controls || {};
 
-App.Controls.FileDropper = function(
-	$fileInput,
-	_,
-	jQuery) {
+App.Controls.FileDropper = function($fileInput) {
+	var _ = App.DI.get('_');
+	var jQuery = App.DI.get('jQuery');
 
 	var options = {
 		onChange: null,
@@ -63,7 +62,4 @@ App.Controls.FileDropper = function(
 	});
 
 	return options;
-
 };
-
-App.DI.register('fileDropper', App.Controls.FileDropper);
diff --git a/public_html/js/Controls/TagInput.js b/public_html/js/Controls/TagInput.js
index d2c8bd52..1c1fa5db 100644
--- a/public_html/js/Controls/TagInput.js
+++ b/public_html/js/Controls/TagInput.js
@@ -1,12 +1,9 @@
 var App = App || {};
 App.Controls = App.Controls || {};
 
-//todo: autocomplete
-
-App.Controls.TagInput = function(
-	$underlyingInput,
-	_,
-	jQuery) {
+App.Controls.TagInput = function($underlyingInput) {
+	var _ = App.DI.get('_');
+	var jQuery = App.DI.get('jQuery');
 
 	var KEY_RETURN = 13;
 	var KEY_SPACE = 32;
@@ -48,21 +45,36 @@ App.Controls.TagInput = function(
 	});
 	$input.attr('placeholder', $underlyingInput.attr('placeholder'));
 
-	var tagsToAdd = $underlyingInput.val().split(/\s+/);
-	_.map(tagsToAdd, addTag);
+	addTagsFromText($underlyingInput.val());
 	$underlyingInput.val('');
 
-	$input.unbind('focus').bind('focus', function(e) {
+	initAutocomplete();
+
+	function initAutocomplete() {
+		var autocomplete = new App.Controls.AutoCompleteInput($input);
+		autocomplete.onApply = function(text) {
+			addTagsFromText(text);
+			$input.val('');
+		};
+		autocomplete.additionalFilter = function(results) {
+			var tags = getTags();
+			return _.filter(results, function(resultItem) {
+				return !_.contains(tags, resultItem[0]);
+			});
+		};
+	}
+
+	$input.bind('focus', function(e) {
 		$wrapper.addClass('focused');
 	});
-	$input.unbind('blur').bind('blur', function(e) {
+	$input.bind('blur', function(e) {
 		$wrapper.removeClass('focused');
 		var tag = $input.val();
 		addTag(tag);
 		$input.val('');
 	});
 
-	$input.unbind('paste').bind('paste', function(e) {
+	$input.bind('paste', function(e) {
 		e.preventDefault();
 		var pastedText;
 		if (window.clipboardData) {
@@ -82,7 +94,7 @@ App.Controls.TagInput = function(
 		$input.val(lastTag);
 	});
 
-	$input.unbind('keydown').bind('keydown', function(e) {
+	$input.bind('keydown', function(e) {
 		if (_.contains(inputConfirmKeys, e.which) && !$input.val()) {
 			e.preventDefault();
 			if (typeof(options.inputConfirmed) !== 'undefined') {
@@ -99,6 +111,11 @@ App.Controls.TagInput = function(
 		}
 	});
 
+	function addTagsFromText(text) {
+		var tagsToAdd = text.split(/\s+/);
+		_.map(tagsToAdd, addTag);
+	}
+
 	function addTag(tag) {
 		tag = tag.trim();
 		if (tag.length === 0) {
@@ -185,5 +202,3 @@ App.Controls.TagInput = function(
 	});
 	return options;
 };
-
-App.DI.register('tagInput', App.Controls.TagInput);
diff --git a/public_html/js/Presenters/PostListPresenter.js b/public_html/js/Presenters/PostListPresenter.js
index 52367a7a..de1e21a2 100644
--- a/public_html/js/Presenters/PostListPresenter.js
+++ b/public_html/js/Presenters/PostListPresenter.js
@@ -70,6 +70,7 @@ App.Presenters.PostListPresenter = function(
 	function render() {
 		$el.html(templates.list());
 		$searchInput = $el.find('input[name=query]');
+		App.Controls.AutoCompleteInput($searchInput);
 
 		$searchInput.val(searchArgs.query);
 		$searchInput.keydown(searchInputKeyPressed);
@@ -80,7 +81,7 @@ App.Presenters.PostListPresenter = function(
 		});
 
 		keyboard.keyup('q', function() {
-			$searchInput.eq(0).focus();
+			$searchInput.eq(0).focus().select();
 		});
 	}
 
@@ -95,7 +96,7 @@ App.Presenters.PostListPresenter = function(
 			var $post = jQuery('<li>' + templates.listItem({
 				searchArgs: searchArgs,
 				post: post,
-			}) + '</li>')
+			}) + '</li>');
 			util.loadImagesNicely($post.find('img'));
 			$target.append($post);
 		});
@@ -116,7 +117,7 @@ App.Presenters.PostListPresenter = function(
 	function updateSearch() {
 		$searchInput.blur();
 		pagerPresenter.setSearchParams({
-			query: $searchInput.val(),
+			query: $searchInput.val().trim(),
 			order: searchArgs.order});
 	}
 
diff --git a/public_html/js/Presenters/PostPresenter.js b/public_html/js/Presenters/PostPresenter.js
index 3004af90..2edef41c 100644
--- a/public_html/js/Presenters/PostPresenter.js
+++ b/public_html/js/Presenters/PostPresenter.js
@@ -135,14 +135,14 @@ App.Presenters.PostPresenter = function(
 		$messages = $el.find('.messages');
 
 		if (editPrivileges.canChangeTags) {
-			tagInput = App.Controls.TagInput($el.find('form [name=tags]'), _, jQuery);
+			tagInput = new App.Controls.TagInput($el.find('form [name=tags]'));
 			tagInput.inputConfirmed = editPost;
 		}
 
-		postContentFileDropper = new App.Controls.FileDropper($el.find('form [name=content]'), _, jQuery);
+		postContentFileDropper = new App.Controls.FileDropper($el.find('form [name=content]'));
 		postContentFileDropper.onChange = postContentChanged;
 		postContentFileDropper.setNames = true;
-		postThumbnailFileDropper = new App.Controls.FileDropper($el.find('form [name=thumbnail]'), _, jQuery);
+		postThumbnailFileDropper = new App.Controls.FileDropper($el.find('form [name=thumbnail]'));
 		postThumbnailFileDropper.onChange = postThumbnailChanged;
 		postThumbnailFileDropper.setNames = true;
 
diff --git a/public_html/js/Presenters/PostUploadPresenter.js b/public_html/js/Presenters/PostUploadPresenter.js
index 0d1bbcfc..ebae81f4 100644
--- a/public_html/js/Presenters/PostUploadPresenter.js
+++ b/public_html/js/Presenters/PostUploadPresenter.js
@@ -41,8 +41,8 @@ App.Presenters.PostUploadPresenter = function(
 		}));
 		$messages = $el.find('.messages');
 
-		tagInput = new App.Controls.TagInput($el.find('form [name=tags]'), _, jQuery);
-		fileDropper = App.Controls.FileDropper($el.find('[name=post-content]'), _, jQuery);
+		tagInput = new App.Controls.TagInput($el.find('form [name=tags]'));
+		fileDropper = new App.Controls.FileDropper($el.find('[name=post-content]'));
 		fileDropper.onChange = fileHandlerChanged;
 
 		$el.find('.url-handler input').keydown(urlHandlerKeyPressed);
diff --git a/public_html/js/Presenters/UserAccountSettingsPresenter.js b/public_html/js/Presenters/UserAccountSettingsPresenter.js
index 10b28caf..05c2e546 100644
--- a/public_html/js/Presenters/UserAccountSettingsPresenter.js
+++ b/public_html/js/Presenters/UserAccountSettingsPresenter.js
@@ -54,7 +54,7 @@ App.Presenters.UserAccountSettingsPresenter = function(
 		$el.find('form').submit(accountSettingsFormSubmitted);
 		$el.find('form [name=avatar-style]').change(avatarStyleChanged);
 		avatarStyleChanged();
-		fileDropper = new App.Controls.FileDropper($el.find('[name=avatar-content]'), _, jQuery);
+		fileDropper = new App.Controls.FileDropper($el.find('[name=avatar-content]'));
 		fileDropper.onChange = avatarContentChanged;
 		fileDropper.setNames = true;
 	}
diff --git a/public_html/js/Services/TagList.js b/public_html/js/Services/TagList.js
new file mode 100644
index 00000000..6ba1691d
--- /dev/null
+++ b/public_html/js/Services/TagList.js
@@ -0,0 +1,27 @@
+var App = App || {};
+App.Services = App.Services || {};
+
+App.Services.TagList = function(jQuery) {
+	var tags = [];
+
+	jQuery.ajax({
+		success: function(data, textStatus, xhr) {
+			tags = data;
+		},
+		error: function(xhr, textStatus, errorThrown) {
+			console.log(new Error(errorThrown));
+		},
+		type: 'GET',
+		url: '/data/tags.json',
+	});
+
+	function getTags() {
+		return tags;
+	}
+
+	return {
+		getTags: getTags,
+	};
+};
+
+App.DI.registerSingleton('tagList', ['jQuery'], App.Services.TagList);