diff --git a/index.html b/index.html
index 319e62b..df8a198 100644
--- a/index.html
+++ b/index.html
@@ -15,6 +15,7 @@
     <script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.5.2/underscore-min.js"></script>
     <script type="text/javascript" src="js/localstorage.js"></script>
     <script type="text/javascript" src="js/weechat.js"></script>
+    <script type="text/javascript" src="js/irc-utils.js"></script>
     <script type="text/javascript" src="js/websockets.js"></script>
     <script type="text/javascript" src="js/models.js"></script>
     <script type="text/javascript" src="js/plugins.js"></script>
diff --git a/js/irc-utils.js b/js/irc-utils.js
new file mode 100644
index 0000000..7942c21
--- /dev/null
+++ b/js/irc-utils.js
@@ -0,0 +1,174 @@
+/**
+ * Portable utilities for IRC.
+ */
+
+var IrcUtils = {
+    /**
+     * Completes a single nick.
+     *
+     * @param candidate What to search for
+     * @param nickList Array of current nicks sorted alphabetically
+     * @return Completed nick (null if not found)
+     */
+    _completeSingleNick: function(candidate, nickList) {
+        var foundNick = null;
+
+        nickList.some(function(nick) {
+            if (nick.search(candidate) == 0) {
+                // found!
+                foundNick = nick;
+                return true;
+            }
+            return false;
+        });
+
+        return foundNick;
+    },
+
+    /**
+     * Get the next nick when iterating nicks.
+     *
+     * @param iterCandidate First characters to look at
+     * @param currentNick Current selected nick
+     * @param nickList Array of current nicks sorted alphabetically
+     * @return Next nick (may be the same)
+     */
+    _nextNick: function(iterCandidate, currentNick, nickList) {
+        var firstInGroup = null;
+        var matchingNicks = [];
+        var at = null;
+
+        // collect matching nicks
+        for (var i = 0; i < nickList.length; ++i) {
+            if (nickList[i].search(iterCandidate) == 0) {
+                matchingNicks.push(nickList[i]);
+                if (currentNick == nickList[i]) {
+                    at = matchingNicks.length - 1;
+                }
+            } else if (matchingNicks.length > 0) {
+                // end of group, no need to check after this
+                break;
+            }
+        }
+
+        if (at == null || matchingNicks.length == 0) {
+            return currentNick;
+        } else {
+            ++at;
+            if (at == matchingNicks.length) {
+                // cycle
+                at = 0;
+            }
+            return matchingNicks[at];
+        }
+    },
+
+    /**
+     * Nicks tab completion.
+     *
+     * @param text Plain text (no colors)
+     * @param caretPos Current caret position (0 means before the first character)
+     * @param doIterate True to iterate the nicks if possible
+     * @param iterCandidate Current iteration candidate (null if not iterating)
+     * @param nickList Array of current nicks sorted alphabetically
+     * @return Object with following properties:
+     *      text: new complete replacement text
+     *      caretPos: new caret position within new text
+     *      foundNick: completed nick (or null if not possible)
+     *      iterCandidate: current iterating candidate
+     */
+    completeNick: function(text, caretPos, doIterate, iterCandidate, nickList) {
+        // text before and after caret
+        var beforeCaret = text.substring(0, caretPos);
+        var afterCaret = text.substring(caretPos);
+
+        // default: don't change anything
+        var ret = {
+            text: text,
+            caretPos: caretPos,
+            foundNick: null,
+            iterCandidate: null
+        };
+
+        // iterating nicks at the beginning?
+        var m = beforeCaret.match(/^([a-zA-Z0-9_\\\[\]{}^`|-]+): $/);
+        if (m) {
+            if (doIterate) {
+                // try iterating
+                var newNick = IrcUtils._nextNick(iterCandidate, m[1], nickList);
+                beforeCaret = newNick + ': ';
+                return {
+                    text: beforeCaret + afterCaret,
+                    caretPos: beforeCaret.length,
+                    foundNick: newNick,
+                    iterCandidate: iterCandidate
+                };
+            } else {
+                // if not iterating, don't do anything
+                return ret;
+            }
+        }
+
+        // nick completion in the beginning?
+        m = beforeCaret.match(/^([a-zA-Z0-9_\\\[\]{}^`|-]+)$/);
+        if (m) {
+            // try completing
+            var newNick = IrcUtils._completeSingleNick(m[1], nickList);
+            if (newNick === null) {
+                // no match
+                return ret;
+            }
+            beforeCaret = newNick + ': ';
+            if (afterCaret[0] == ' ') {
+                // swallow first space after caret if any
+                afterCaret = afterCaret.substring(1);
+            }
+            return {
+                text: beforeCaret + afterCaret,
+                caretPos: beforeCaret.length,
+                foundNick: newNick,
+                iterCandidate: m[1]
+            };
+        }
+
+        // iterating nicks in the middle?
+        m = beforeCaret.match(/^(.* )([a-zA-Z0-9_\\\[\]{}^`|-]+) $/);
+        if (m) {
+            if (doIterate) {
+                // try iterating
+                var newNick = IrcUtils._nextNick(iterCandidate, m[2], nickList);
+                beforeCaret = m[1] + newNick + ' ';
+                return {
+                    text: beforeCaret + afterCaret,
+                    caretPos: beforeCaret.length,
+                    foundNick: newNick,
+                    iterCandidate: iterCandidate
+                };
+            } else {
+                // if not iterating, don't do anything
+                return ret;
+            }
+        }
+
+        // nick completion elsewhere in the middle?
+        m = beforeCaret.match(/^(.* )([a-zA-Z0-9_\\\[\]{}^`|-]+)$/);
+        if (m) {
+            // try completing
+            var newNick = IrcUtils._completeSingleNick(m[2], nickList);
+            if (newNick === null) {
+                // no match
+                return ret;
+            }
+            beforeCaret = m[1] + newNick + ' ';
+            return {
+                text: beforeCaret + afterCaret,
+                caretPos: beforeCaret.length,
+                foundNick: newNick,
+                iterCandidate: m[2]
+            };
+        }
+
+        // completion not possible
+        return ret;
+    }
+};