--- a/browser/components/aboutconfig/content/aboutconfig.js
+++ b/browser/components/aboutconfig/content/aboutconfig.js
@@ -1,16 +1,20 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+ChromeUtils.import("resource://gre/modules/DeferredTask.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 ChromeUtils.import("resource://gre/modules/Preferences.jsm");
 
+const SEARCH_TIMEOUT_MS = 500;
+
 let gDefaultBranch = Services.prefs.getDefaultBranch("");
+let gFilterPrefsTask = new DeferredTask(() => filterPrefs(), SEARCH_TIMEOUT_MS);
 
 /**
  * Maps the name of each preference in the back-end to its PrefRow object,
  * separating the preferences that actually exist. This is as an optimization to
  * avoid querying the preferences service each time the list is filtered.
  */
 let gExistingPrefs = new Map();
 let gDeletedPrefs = new Map();
@@ -284,22 +288,33 @@ function loadPrefs() {
   let prefs = document.createElement("table");
   prefs.id = "prefs";
   document.body.appendChild(prefs);
 
   for (let name of Services.prefs.getChildList("")) {
     new PrefRow(name);
   }
 
-  search.addEventListener("keypress", e => {
-    if (e.key == "Enter") {
-      filterPrefs();
+  search.addEventListener("keypress", event => {
+    switch (event.key) {
+      case "Escape":
+        search.value = "";
+        // Fall through.
+      case "Enter":
+        gFilterPrefsTask.disarm();
+        filterPrefs();
     }
   });
 
+  search.addEventListener("input", () => {
+    // We call "disarm" to restart the timer at every input.
+    gFilterPrefsTask.disarm();
+    gFilterPrefsTask.arm();
+  });
+
   prefs.addEventListener("click", event => {
     if (event.target.localName != "button") {
       return;
     }
     let pref = gElementToPrefMap.get(event.target.closest("tr"));
     let button = event.target.closest("button");
     if (button.classList.contains("button-add")) {
       Preferences.set(pref.name, pref.value);

--- a/browser/components/aboutconfig/test/browser/browser_search.js
+++ b/browser/components/aboutconfig/test/browser/browser_search.js
@@ -54,8 +54,36 @@ add_task(async function test_search() {
     Assert.equal(this.rows.length, 2);
 
     // When searching case insensitively, there is an additional row to add a
     // new preference with the same name but a different case.
     this.search("TEST.aboutconfig.a");
     Assert.equal(this.rows.length, 3);
   });
 });
+
+add_task(async function test_search_delayed() {
+  await AboutConfigTest.withNewTab(async function() {
+    let prefs = this.document.getElementById("prefs");
+
+    // Prepare the table and the search field for the test.
+    this.search("test.aboutconfig.a");
+    Assert.equal(this.rows.length, 2);
+
+    // The table is updated in a single microtask, so we don't need to wait for
+    // specific mutations, we can just continue when the children are updated.
+    let prefsTableChanged = new Promise(resolve => {
+      let observer = new MutationObserver(() => {
+        observer.disconnect();
+        resolve();
+      });
+      observer.observe(prefs, { childList: true });
+    });
+
+    // Add a character and test that the table is not updated immediately.
+    EventUtils.synthesizeKey("b");
+    Assert.equal(this.rows.length, 2);
+
+    // The table will eventually be updated after a delay.
+    await prefsTableChanged;
+    Assert.equal(this.rows.length, 1);
+  });
+});