diff --git a/chrome/content/zotero/xpcom/data/dataObject.js b/chrome/content/zotero/xpcom/data/dataObject.js
index 4bc9423c48..a3f12309ab 100644
--- a/chrome/content/zotero/xpcom/data/dataObject.js
+++ b/chrome/content/zotero/xpcom/data/dataObject.js
@@ -1335,10 +1335,10 @@ Zotero.DataObject.prototype.toResponseJSON = function (options = {}) {
 				href: Zotero.URI.toAPIURL(uri, options.apiURL),
 				type: 'application/json'
 			},
-			alternate: {
+			alternate: Zotero.Users.getCurrentUserID() ? {
 				href: Zotero.URI.toWebURL(uri),
 				type: 'text/html'
-			}
+			} : undefined
 		},
 		meta: {},
 		data: this.toJSON(options)
diff --git a/chrome/content/zotero/xpcom/data/library.js b/chrome/content/zotero/xpcom/data/library.js
index a1dcd74f2a..24884a9013 100644
--- a/chrome/content/zotero/xpcom/data/library.js
+++ b/chrome/content/zotero/xpcom/data/library.js
@@ -136,7 +136,7 @@ Zotero.defineProperty(Zotero.Library.prototype, 'libraryTypeID', {
 	get: function () {
 		switch (this._libraryType) {
 		case 'user':
-			return Zotero.Users.getCurrentUserID();
+			return Zotero.Users.getCurrentUserID() || 0;
 		
 		case 'group':
 			return Zotero.Groups.getGroupIDFromLibraryID(this._libraryID);
@@ -689,10 +689,10 @@ Zotero.Library.prototype.toResponseJSON = function (options = {}) {
 				href: Zotero.URI.toAPIURL(uri, options.apiURL),
 				type: 'application/json'
 			},
-			alternate: {
+			alternate: Zotero.Users.getCurrentUserID() ? {
 				href: Zotero.URI.toWebURL(uri),
 				type: 'text/html'
-			}
+			} : undefined
 		}
 	};
 };
diff --git a/chrome/content/zotero/xpcom/data/tags.js b/chrome/content/zotero/xpcom/data/tags.js
index 8da35248bd..c1d1702924 100644
--- a/chrome/content/zotero/xpcom/data/tags.js
+++ b/chrome/content/zotero/xpcom/data/tags.js
@@ -253,10 +253,10 @@ Zotero.Tags = new function() {
 						href: Zotero.URI.toAPIURL(uri),
 						type: 'application/json'
 					},
-					alternate: {
+					alternate: Zotero.Users.getCurrentUserID() ? {
 						href: uri, // No toWebURL - match dataserver behavior
 						type: 'text/html'
-					}
+					} : undefined
 				},
 				meta: {
 					type: tag.type || 0,
diff --git a/chrome/content/zotero/xpcom/localAPI/server_localAPI.js b/chrome/content/zotero/xpcom/localAPI/server_localAPI.js
index 674e613616..f9f5a09e13 100644
--- a/chrome/content/zotero/xpcom/localAPI/server_localAPI.js
+++ b/chrome/content/zotero/xpcom/localAPI/server_localAPI.js
@@ -101,7 +101,12 @@ class LocalAPIEndpoint {
 		if (userID !== undefined
 				&& userID != 0
 				&& userID != Zotero.Users.getCurrentUserID()) {
-			return this.makeResponse(400, 'text/plain', 'Only data for the logged-in user is available locally - use userID 0');
+			let suffix = "";
+			let currentUserID = Zotero.Users.getCurrentUserID();
+			if (currentUserID) {
+				suffix += " or " + currentUserID;
+			}
+			return this.makeResponse(400, 'text/plain', 'Only data for the logged-in user is available locally -- use userID 0' + suffix);
 		}
 
 		requestData.libraryID = requestData.pathParams.groupID
@@ -273,10 +278,11 @@ class LocalAPIEndpoint {
 			}
 		}
 
-		// alternate: cut off '/api/', replace userID 0 with current user's ID
-		links.alternate = ZOTERO_CONFIG.WWW_BASE_URL
-			+ requestData.pathname.substring(5)
+		// alternate: only include if logged in, cut off '/api/', replace userID 0 with current userID
+		if (Zotero.Users.getCurrentUserID()) {
+			links.alternate = ZOTERO_CONFIG.WWW_BASE_URL + requestData.pathname.substring(5)
 				.replace('users/0/', `users/${Zotero.Users.getCurrentUserID()}/`);
+		}
 		
 		return links;
 	}
diff --git a/chrome/content/zotero/xpcom/uri.js b/chrome/content/zotero/xpcom/uri.js
index 1fcf85c791..766c743808 100644
--- a/chrome/content/zotero/xpcom/uri.js
+++ b/chrome/content/zotero/xpcom/uri.js
@@ -359,7 +359,10 @@ Zotero.URI = new function () {
 		if (!apiURL) {
 			apiURL = ZOTERO_CONFIG.API_URL;
 		}
-		return uri.replace(ZOTERO_CONFIG.BASE_URI, apiURL);
+		return uri
+			.replace(ZOTERO_CONFIG.BASE_URI, apiURL)
+			// Replace local user key with users/0
+			.replace(/(http:\/\/localhost:\d+\/api\/users)\/local\/\w+/, '$1/0');
 	};
 
 	/**