diff --git a/netlink-html.pl b/netlink-html.pl
index 65b055f..ebec88c 100755
--- a/netlink-html.pl
+++ b/netlink-html.pl
@@ -333,6 +333,7 @@ sub write_html_hier_files {
 	html_header($html, "OpenBSD Netlink Hierarchie",
 	    "OpenBSD netlink $short test results",
 	    @nav);
+	print $html "<script src='/tables.js'></script>\n";
 
 	my @hv = sort { $a->{key} cmp $b->{key} } @{$H{$date}};
 	html_hier_top($html, $date, @hv);
diff --git a/tables.js b/tables.js
new file mode 100644
index 0000000..5e3a9fc
--- /dev/null
+++ b/tables.js
@@ -0,0 +1,157 @@
+/*
+* Copyright (c) 2024 Moritz Buhl <mbuhl@moritzbuhl.de>
+*
+* Permission to use, copy, modify, and distribute this software for any
+* purpose with or without fee is hereby granted, provided that the above
+* copyright notice and this permission notice appear in all copies.
+*
+* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+'use strict';
+
+function merge_rows() {
+    const utilization = document.getElementsByClassName('utilization')[0];
+    const otbody = utilization.children[1];
+    const tbody = otbody.cloneNode(1);
+
+    let otr = [];
+    for (const trc of tbody.children) {
+	const tr = trc.children;
+	const len = trc.childElementCount;
+	if (!otr.length) {
+	    for (let i = 0; i < len; i++) {
+		otr[i] = tr[i];
+	    }
+	    continue;
+	}
+
+	if (len != otr.length) {
+	    console.warn(`inhomogeneous cell count: ${len} vs ${otr.length}.`);
+	    return;
+	}
+	for (let i = 0; i < len; i++) {
+	    if (tr[i].innerText && otr[i].innerText == tr[i].innerText) {
+		let rowspan = Number(otr[i].getAttribute('rowspan'));
+		if (!rowspan) {
+		    rowspan = 1;
+		}
+		otr[i].setAttribute('rowspan', rowspan + 1);
+		tr[i].hidden = 1;
+	    } else {
+		tr[i].hidden = 0;
+		otr[i] = tr[i];
+	    }
+	}
+    }
+
+    otbody.replaceWith(tbody);
+}
+
+function sort_by_col(ev) {
+    const utilization = document.getElementsByClassName('utilization')[0];
+    const otbody = utilization.children[1];
+    const tbody = otbody.cloneNode(0);
+    const thead = utilization.children[0].children[0].children;
+    let col;
+    let rows = [];
+
+    for (col = 0; col < thead.length; col++) {
+	if (thead[col] == ev.target) break;
+    }
+
+    for (const tr of otbody.children) {
+	rows.push(tr);
+    }
+
+    rows.sort((a,b) => {
+	let c = col;
+	do {
+	    if (c > 5)
+		c = 1;
+	    if (a.children[c].innerText == b.children[c].innerText) {
+		c++;
+	    } else
+		break;
+	} while (c != col);
+
+	/* XXX: return >= depending on arrow */
+	return a.children[c].innerText < b.children[c].innerText;
+    });
+
+    for (const tr of rows) {
+	tbody.appendChild(tr);
+    }
+
+    tbody.innerHTML = tbody.innerHTML.replaceAll('hidden=""', '').replaceAll(
+	'rowspan=', 'foo='); // XXX
+
+    otbody.replaceWith(tbody);
+    merge_rows();
+}
+
+function filter_by_target(ev) {
+    const utilization = document.getElementsByClassName('utilization')[0];
+    const otbody = utilization.children[1];
+    const tbody = otbody.cloneNode(0);
+    const par = ev.target.parentElement.children;
+    let col;
+    let match = [], others = [];
+
+    for (col = 0; col < par.length; col++) {
+	if (par[col] == ev.target) break;
+    }
+
+    for (const tr of otbody.children) {
+	if (tr.children[col].innerText == ev.target.innerText)
+	    match.push(tr);
+	else
+	    others.push(tr);
+    }
+
+    for (const tr of match) {
+	tbody.appendChild(tr);
+    }
+    for (const tr of others) {
+	tbody.appendChild(tr);
+    }
+
+    tbody.innerHTML = tbody.innerHTML.replaceAll('hidden=""', '').replaceAll(
+	'rowspan=', 'foo='); // XXX
+
+    otbody.replaceWith(tbody);
+    merge_rows();
+    const descs = utilization.children[1].getElementsByClassName('desc');
+    for (let i = 0; i < descs.length; i++) {
+	let td = descs[i];
+	td.onclick = filter_by_target;
+    }
+}
+
+window.addEventListener("load", () => {
+    merge_rows();
+    const utilization = document.getElementsByClassName('utilization')[0];
+    const thead_tr = utilization.children[0].children[0].children;
+    const descs = utilization.children[1].getElementsByClassName('desc');
+
+    thead_tr[1].innerHTML = "IP";
+    thead_tr[2].innerHTML = "Transport";
+    thead_tr[3].innerHTML = "Direction";
+    thead_tr[4].innerHTML = "Test";
+    thead_tr[5].innerHTML = "Modifier";
+    for (let i = 1; i <= 5; i++) {
+	thead_tr[i].innerHTML += " &rarr;";
+	thead_tr[i].classList.add("desc");
+	/* XXX: add on-click listeners for td.descs */
+	thead_tr[i].addEventListener("click", sort_by_col);
+    }
+    for (let i = 0; i < descs.length; i++) {
+	let td = descs[i];
+	td.onclick = filter_by_target;
+    }
+});