<p></p>
<p><b>@gravitystorm</b> commented on this pull request.</p>

<p>I realise that this is going upstream, and for the variable naming etc they will have their own preferences. But here's a small review anyway, and I think the url changes are worth highlighting.</p><hr>

<p>In <a href="https://github.com/openstreetmap/openstreetmap-website/pull/2584#discussion_r406659831">vendor/assets/leaflet/leaflet.osm.js</a>:</p>
<pre style='color:#555'>> @@ -1,8 +1,25 @@
 L.OSM = {};
 
+var h2 = false;
</pre>
<p>I'd choose <code>http2</code> as the variable name, for clarity. I think <code>h2</code> is a bit obscure.</p>

<hr>

<p>In <a href="https://github.com/openstreetmap/openstreetmap-website/pull/2584#discussion_r406683619">vendor/assets/leaflet/leaflet.osm.js</a>:</p>
<pre style='color:#555'>> @@ -1,8 +1,25 @@
 L.OSM = {};
 
+var h2 = false;
+// tile.openstreetmap.org supports http/2 where sharding makes no sense.
+// Use only one subdomain if we're using http/2
+if (
+    (window.performance && window.performance.getEntries      && performance.getEntries()[0].nextHopProtocol == 'h2') ||
+    (window.performance && performance.timing.nextHopProtocol && performance.timing.nextHopProtocol          == 'h2') ||
+    (window.chrome      && window.chrome.loadTimes            && window.chrome.loadTimes().connectionInfo    == 'h2')
+) {
+    h2 = true;
+}
+
+if (h2) {
+    var osmtileurl = 'https://a.tile.openstreetmap.org/{z}/{x}/{y}.png';
</pre>
<p>I recommend using <code>tile.openstreetmap.org</code> if you don't need the abc subdomains, since the <code>a</code> is just an artifact of the load distribution that this patch moves away from.</p>

<hr>

<p>In <a href="https://github.com/openstreetmap/openstreetmap-website/pull/2584#discussion_r406683723">vendor/assets/leaflet/leaflet.osm.js</a>:</p>
<pre style='color:#555'>> @@ -44,9 +61,14 @@ L.OSM.HOT = L.OSM.TileLayer.extend({
   }
 });
 
+if(h2) {
+    var osmgpsurl = 'https://gps-a.tile.openstreetmap.org/lines/{z}/{x}/{y}.png';
</pre>
<p>As above - <code>gps.tile.openstreetmap.org</code> is sufficient</p>

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