--- a/browser/components/preferences/connection.js
+++ b/browser/components/preferences/connection.js
@@ -37,16 +37,17 @@ Preferences.addAll([
   { id: "network.trr.uri", type: "string" },
 ]);
 
 window.addEventListener("DOMContentLoaded", () => {
   Preferences.get("network.proxy.type").on("change",
     gConnectionsDialog.proxyTypeChanged.bind(gConnectionsDialog));
   Preferences.get("network.proxy.socks_version").on("change",
     gConnectionsDialog.updateDNSPref.bind(gConnectionsDialog));
+  gConnectionsDialog.initDnsOverHttpsUI();
 
   document
     .getElementById("disableProxyExtension")
     .addEventListener(
       "command", makeDisableControllingExtension(
         PREF_SETTING_TYPE, PROXY_KEY).bind(gConnectionsDialog));
   gConnectionsDialog.updateProxySettingsUI();
   initializeProxyUI(gConnectionsDialog);
@@ -305,9 +306,14 @@ var gConnectionsDialog = {
 
   writeDnsOverHttpsUri() {
     // called to update pref with user input
     let input = document.getElementById("networkDnsOverHttpsUrl");
     let uriString = input.value.trim();
     // turn an empty string into `undefined` to clear the pref back to the default
     return uriString.length ? uriString : undefined;
   },
+
+  initDnsOverHttpsUI() {
+    let input = document.getElementById("networkDnsOverHttpsUrl");
+    input.placeholder = Preferences.get("network.trr.uri").defaultValue;
+  },
 };

--- a/browser/components/preferences/connection.xul
+++ b/browser/components/preferences/connection.xul
@@ -154,14 +154,13 @@
               data-l10n-id="connection-dns-over-https"
               preference="network.trr.mode"
               onsyncfrompreference="return gConnectionsDialog.readDnsOverHttpsMode();"
               onsynctopreference="return gConnectionsDialog.writeDnsOverHttpsMode()" />
     <hbox class="indent" flex="1" align="center">
       <label control="networkDnsOverHttpsUrl" data-l10n-id="connection-dns-over-https-url"
              data-l10n-attrs="tooltiptext"/>
       <textbox id="networkDnsOverHttpsUrl" flex="1" preference="network.trr.uri"
-               placeholder="https://doh.example.com/dns-query"
                onsynctopreference="return gConnectionsDialog.writeDnsOverHttpsUri()" />
     </hbox>
     <separator/>
   </vbox>
 </dialog>

--- a/browser/components/preferences/in-content/tests/browser_connection_dnsoverhttps.js
+++ b/browser/components/preferences/in-content/tests/browser_connection_dnsoverhttps.js
@@ -3,17 +3,17 @@ ChromeUtils.import("resource://gre/modul
 const SUBDIALOG_URL = "chrome://browser/content/preferences/connection.xul";
 const TRR_MODE_PREF = "network.trr.mode";
 const TRR_URI_PREF = "network.trr.uri";
 
 const modeCheckboxSelector = "#networkDnsOverHttps";
 const uriTextboxSelector = "#networkDnsOverHttpsUrl";
 const defaultPrefValues = Object.freeze({
   [TRR_MODE_PREF]: 0,
-  [TRR_URI_PREF]: "",
+  [TRR_URI_PREF]: "https://mozilla.cloudflare-dns.com/dns-query",
 });
 
 function resetPrefs() {
   Services.prefs.clearUserPref(TRR_MODE_PREF);
   Services.prefs.clearUserPref(TRR_URI_PREF);
 }
 
 let preferencesOpen = new Promise(res => open_preferences(res));
@@ -122,30 +122,30 @@ add_task(async function default_values()
   is(modePref, defaultPrefValues[TRR_MODE_PREF],
      `Actual value of ${TRR_MODE_PREF} matches expected default value`);
   is(uriPref, defaultPrefValues[TRR_URI_PREF],
      `Actual value of ${TRR_MODE_PREF} matches expected default value`);
 });
 
 let testVariations = [
   // verify state with defaults
-  { expectedModePref: 0, expectedUriValue: "" },
+  { expectedModePref: 0, expectedUriValue: "https://mozilla.cloudflare-dns.com/dns-query" },
 
   // verify each of the modes maps to the correct checked state
   { [TRR_MODE_PREF]: 0, expectedModeChecked: false },
   { [TRR_MODE_PREF]: 1, expectedModeChecked: true },
   { [TRR_MODE_PREF]: 2, expectedModeChecked: true },
   { [TRR_MODE_PREF]: 3, expectedModeChecked: true },
   { [TRR_MODE_PREF]: 4, expectedModeChecked: true },
   { [TRR_MODE_PREF]: 5, expectedModeChecked: false },
   // verify an out of bounds mode value maps to the correct checked state
   { [TRR_MODE_PREF]: 77, expectedModeChecked: false },
 
   // verify toggling the checkbox gives the right outcomes
-  { clickMode: true, expectedModeValue: 2, expectedUriValue: "" },
+  { clickMode: true, expectedModeValue: 2, expectedUriValue: "https://mozilla.cloudflare-dns.com/dns-query" },
   {
     [TRR_MODE_PREF]: 4,
     expectedModeChecked: true, clickMode: true, expectedModePref: 0,
   },
   {
     [TRR_MODE_PREF]: 2, [TRR_URI_PREF]: "https://example.com",
     expectedModeValue: true, expectedUriValue: "https://example.com",
   },

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -5428,17 +5428,17 @@ pref("network.captive-portal-service.max
 // Every 10 checks, the delay is increased by a factor of 5
 pref("network.captive-portal-service.backoffFactor", "5.0");
 pref("network.captive-portal-service.enabled", false);
 
 // DNS Trusted Recursive Resolver
 // 0 - default off, 1 - race, 2 TRR first, 3 TRR only, 4 shadow, 5 off by choice
 pref("network.trr.mode", 0);
 // DNS-over-HTTP service to use, must be HTTPS://
-pref("network.trr.uri", "");
+pref("network.trr.uri", "https://mozilla.cloudflare-dns.com/dns-query");
 // credentials to pass to DOH end-point
 pref("network.trr.credentials", "");
 // Wait for captive portal confirmation before enabling TRR
 #if defined(ANDROID)
 // On Android, the captive portal is handled by the OS itself
 pref("network.trr.wait-for-portal", false);
 #else
 pref("network.trr.wait-for-portal", true);