diff --git a/core/modules/filters/url-ops.js b/core/modules/filters/url-ops.js
new file mode 100644
index 000000000..392e510be
--- /dev/null
+++ b/core/modules/filters/url-ops.js
@@ -0,0 +1,39 @@
+/*\
+title: $:/core/modules/filters/url-ops.js
+type: application/javascript
+module-type: filteroperator
+
+Filter operators for URL operations
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+exports["setquerystring"] = function(source,operator,options) {
+	var URL = $tw.browser ? window.URL : require("url").URL,
+		URLSearchParams = $tw.browser ? window.URLSearchParams : require("url").URLSearchParams,
+		name = operator.operands.length >= 1 ? operator.operands[0] : null,
+		value = operator.operands.length >= 2 ? operator.operands[1] : "",
+		results = [];
+	source(function(tiddler,title) {
+		var url;
+		try {
+			url = new URL(title);
+		} catch(e) {
+		}
+		if(url) {
+			var params = new URLSearchParams(url.search);
+			if(name) {
+				params.set(name,value);
+			}
+			url.search = params.toString();
+			results.push(url.toString());
+		}
+	});
+	return results;
+};
+
+})();
diff --git a/core/modules/utils/dom/http.js b/core/modules/utils/dom/http.js
index 3eca4985b..6b9ef4bb2 100644
--- a/core/modules/utils/dom/http.js
+++ b/core/modules/utils/dom/http.js
@@ -66,9 +66,9 @@ HttpClient.prototype.handleHttpRequest = function(event) {
 			callback: function(err,data,xhr) {
 				var headers = {};
 				$tw.utils.each(xhr.getAllResponseHeaders().split("\r\n"),function(line) {
-					var parts = line.split(":");
-					if(parts.length === 2) {
-						headers[parts[0].toLowerCase()] = parts[1].trim();
+					var pos = line.indexOf(":");
+					if(pos !== -1) {
+						headers[line.substr(0,pos)] = line.substr(pos + 1).trim();
 					}
 				});
 				setBinding(bindStatus,xhr.status === 200 ? "complete" : "error");
diff --git a/editions/test/tiddlers/tests/data/filters/querystrings.tid b/editions/test/tiddlers/tests/data/filters/querystrings.tid
new file mode 100644
index 000000000..fb3dd7687
--- /dev/null
+++ b/editions/test/tiddlers/tests/data/filters/querystrings.tid
@@ -0,0 +1,27 @@
+title: Filters/QueryStrings
+description: Query string filter operators
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
+title: Output
+
+\define url() https://tiddlywiki.com/
+
+<$let lf={{{ [charcode[10],[13]]}}}>
+
+<$text text={{{
+	[<url>setquerystring[]]
+	[<url>setquerystring[animal],[elephant]]
+	[<url>setquerystring[animal],[elephant]setquerystring[animal],[ostrich]]
+	[<url>setquerystring[animal],[elephant]setquerystring[animal],[ostrich]setquerystring[animal]]
+	+[join<lf>]
+}}}/>
+
+</$let>
++
+title: ExpectedResult
+
+https://tiddlywiki.com/
+https://tiddlywiki.com/?animal=elephant
+https://tiddlywiki.com/?animal=ostrich
+https://tiddlywiki.com/?animal=
\ No newline at end of file
diff --git a/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-http-request Example Zotero.tid b/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-http-request Example Zotero.tid
new file mode 100644
index 000000000..0a05ca6e1
--- /dev/null
+++ b/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-http-request Example Zotero.tid	
@@ -0,0 +1,78 @@
+title: WidgetMessage: tm-http-request Example - Zotero
+tags: $:/tags/Macro
+
+\define zotero-save-item(item)
+<$action-createtiddler
+	$basetitle={{{ =[[_zotero_import ]] =[<item>jsonget[key]] =[[ ]] =[<item>jsonget[title]] +[join[]] }}}
+	text={{{ [<item>jsonget[title]] }}}
+	tags="$:/tags/ZoteroImport"
+>
+	<$action-setmultiplefields $tiddler=<<createTiddler-title>> $fields="[<item>jsonindexes[]addprefix[zotero-]]" $values="[<item>jsonindexes[]] :map[<item>jsonget<currentTiddler>else[.XXXXX.]]"/>
+</$action-createtiddler>
+\end zotero-save-item
+
+\define zotero-save-items(data)
+<$list filter="[<data>jsonindexes[]] :map[<data>jsonextract<currentTiddler>,[data]]" variable="item">
+	<$macrocall $name="zotero-save-item" item=<<item>>/>
+</$list>
+\end zotero-save-items
+
+\define zotero-get-items(start:"0",limit:"25")
+
+\define completion()
+\import [[$:/core/ui/PageMacros]] [all[shadows+tiddlers]tag[$:/tags/Macro]!has[draft.of]]
+	<$action-log msg="In completion"/>
+	<$action-log/>
+	<!-- Success -->
+	<$list filter="[<status>compare:number:gteq[200]compare:number:lteq[299]]" variable="ignore">
+		<!-- Import these items -->
+		<$macrocall $name="zotero-save-items" data=<<data>>/>
+		<!-- Check if there are any more items to download -->
+		<$list filter="[<headers>jsonget[total-results]subtract<start>subtract<limit>compare:number:gt[0]]" variable="ignore">
+			<$macrocall $name="zotero-get-items" start={{{ [<start>add<limit>] }}} limit=<<limit>>/>
+		</$list>
+	</$list>
+\end completion
+
+\define progress()
+\import [[$:/core/ui/PageMacros]] [all[shadows+tiddlers]tag[$:/tags/Macro]!has[draft.of]]
+	<$action-log message="In progress-actions"/>
+\end progress
+
+\define request-url()
+https://api.zotero.org/groups/27508/items/?format=json&sort=title
+\end request-url
+
+<$action-sendmessage
+	$message="tm-http-request"
+	url={{{ [<request-url>setquerystring[start],<__start__>setquerystring[limit],<__limit__>] }}}
+	method="GET"
+	header-accept="application/json"
+	bind-status="$:/temp/zotero/status"
+	bind-progress="$:/temp/zotero/progress"
+	oncompletion=<<completion>>
+	onprogress=<<progress>>
+	var-start=<<__start__>>
+	var-limit=<<__limit__>>
+/>
+\end
+
+\define zotero-actions()
+<$macrocall $name="zotero-get-items" start="0" limit="5"/>
+\end
+
+<$button actions=<<zotero-actions>>>
+Call Zotero
+</$button>
+
+Tiddlers:
+
+<ol>
+<$list filter="[tag[$:/tags/ZoteroImport]]">
+<li>
+<$link>
+<$view field="title"/>
+</$link>
+</li>
+</$list>
+</ol>
diff --git a/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-http-request.tid b/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-http-request.tid
index 5befb6f1b..826ca3032 100644
--- a/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-http-request.tid	
+++ b/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-http-request.tid	
@@ -41,3 +41,7 @@ The following variables are passed to the progress handler:
 |lengthComputable |Whether the progress loaded and total figures are valid - "yes" or "no" |
 |loaded |Number of bytes loaded so far |
 |total |Total number bytes to be loaded |
+
+!! Examples
+
+* [[Zotero's|https://www.zotero.org/]] API for retrieving reference items: [[WidgetMessage: tm-http-request Example - Zotero]]