diff --git a/_locales/en/messages.json b/_locales/en/messages.json
index 95c6ce81..793003bb 100644
--- a/_locales/en/messages.json
+++ b/_locales/en/messages.json
@@ -393,6 +393,10 @@
     "message": "Install",
     "description": "Label for install button"
   },
+  "installButtonInstalled": {
+    "message": "Installed",
+    "description": "Text displayed when the style is successfully installed"
+  },
   "installButtonUpdate": {
     "message": "Update",
     "description": "Label for update button"
diff --git a/content/install-user-css.js b/content/install-user-css.js
index 29d7bc47..dc542c5c 100644
--- a/content/install-user-css.js
+++ b/content/install-user-css.js
@@ -68,7 +68,10 @@ function createSourceLoader() {
 }
 
 function initUsercssInstall() {
-  const pendingSource = createSourceLoader().load();
+  const sourceLoader = createSourceLoader();
+  const pendingSource = sourceLoader.load();
+  let watcher;
+
   chrome.runtime.onConnect.addListener(port => {
     // FIXME: is this the correct way to reject a connection?
     // https://developer.chrome.com/extensions/messaging#connect
@@ -83,6 +86,19 @@ function initUsercssInstall() {
             port.postMessage({method: msg.method + 'Response', error: err.message || String(err)})
           );
           break;
+
+        case 'liveReloadStart':
+          if (!watcher) {
+            watcher = sourceLoader.watch(sourceCode => {
+              port.postMessage({method: 'sourceCodeChanged', sourceCode});
+            });
+          }
+          watcher.start();
+          break;
+
+        case 'liveReloadStop':
+          watcher.stop();
+          break;
       }
     });
   });
diff --git a/install-usercss.html b/install-usercss.html
index b04f9be0..b2f6b78a 100644
--- a/install-usercss.html
+++ b/install-usercss.html
@@ -54,6 +54,10 @@
           <input type="checkbox">
           <span></span>
         </label>
+        <label class="live-reload">
+          <input type="checkbox">
+          <span i18n-text="liveReloadLabel"></span>
+        </label>
       </div>
       <h1>
         <span class="meta-name"></span>
diff --git a/install-usercss/install-usercss.css b/install-usercss/install-usercss.css
index b9bf9307..5e373b30 100644
--- a/install-usercss/install-usercss.css
+++ b/install-usercss/install-usercss.css
@@ -85,6 +85,18 @@ h1 small {
   overflow: hidden;
   overflow-wrap: break-word;
   min-width: 0;
+
+  display: flex;
+  flex-direction: column;
+}
+
+.main > :first-child {
+  flex: 0 0 auto;
+}
+
+.main > :last-child {
+  flex: 1 1 auto;
+  min-height: 0;
 }
 
 .main .code,
diff --git a/install-usercss/install-usercss.js b/install-usercss/install-usercss.js
index fd2ef383..d4597092 100644
--- a/install-usercss/install-usercss.js
+++ b/install-usercss/install-usercss.js
@@ -4,6 +4,8 @@
 
 (function () {
   const params = getParams();
+  let liveReload = false;
+  let installed = false;
 
   const port = chrome.tabs.connect(
     Number(params.tabId),
@@ -19,11 +21,104 @@
           initSourceCode(msg.sourceCode);
         }
         break;
+      case 'sourceCodeChanged':
+        if (msg.error) {
+          alert(msg.error);
+        } else {
+          liveReloadUpdate(msg.sourceCode);
+        }
+        break;
     }
   });
   port.onDisconnect.addListener(closeCurrentTab);
 
   const cm = CodeMirror.fromTextArea($('.code textarea'), {readOnly: true});
+  let liveReloadPending = Promise.resolve();
+
+  function liveReloadUpdate(sourceCode) {
+    liveReloadPending = liveReloadPending.then(() => {
+      const scrollInfo = cm.getScrollInfo();
+      const cursor = cm.getCursor();
+      cm.setValue(sourceCode);
+      cm.setCursor(cursor);
+      cm.scrollTo(scrollInfo.left, scrollInfo.top);
+
+      return runtimeSend({
+        method: 'saveUsercss',
+        reason: 'update',
+        sourceCode
+      }).then(updateMeta).catch(showError);
+    });
+  }
+
+  function updateMeta(style, dup) {
+    $$('.main .warning').forEach(e => e.remove());
+
+    const data = style.usercssData;
+    const dupData = dup && dup.usercssData;
+    const versionTest = dup && semverCompare(data.version, dupData.version);
+
+    // update editor
+    cm.setPreprocessor(data.preprocessor);
+
+    // update metas
+    document.title = `${installButtonLabel()} ${data.name}`;
+
+    $('.install').textContent = installButtonLabel();
+    $('.set-update-url').title = dup && dup.updateUrl && t('installUpdateFrom', dup.updateUrl) || '';
+    $('.meta-name').textContent = data.name;
+    $('.meta-version').textContent = data.version;
+    $('.meta-description').textContent = data.description;
+
+    $('.meta-author').parentNode.style.display = data.author ? '' : 'none';
+    $('.meta-author').textContent = data.author;
+
+    $('.meta-license').parentNode.style.display = data.license ? '' : 'none';
+    $('.meta-license').textContent = data.license;
+
+    $('.applies-to').textContent = '';
+    getAppliesTo(style).forEach(pattern =>
+      $('.applies-to').appendChild($element({tag: 'li', textContent: pattern}))
+    );
+
+    $('.external-link').textContent = '';
+    const externalLink = makeExternalLink();
+    if (externalLink) {
+      $('.external-link').appendChild(externalLink);
+    }
+
+    function makeExternalLink() {
+      const urls = [];
+      if (data.homepageURL) {
+        urls.push([data.homepageURL, t('externalHomepage')]);
+      }
+      if (data.supportURL) {
+        urls.push([data.supportURL, t('externalSupport')]);
+      }
+      if (urls.length) {
+        return $element({appendChild: [
+          $element({tag: 'h3', textContent: t('externalLink')}),
+          $element({tag: 'ul', appendChild: urls.map(args =>
+            $element({tag: 'li', appendChild: makeLink(...args)})
+          )})
+        ]});
+      }
+    }
+
+    function installButtonLabel() {
+      return t(
+        installed ? 'installButtonInstalled' :
+        !dup ? 'installButton' :
+        versionTest > 0 ? 'installButtonUpdate' : 'installButtonReinstall'
+      );
+    }
+  }
+
+  function showError(err) {
+    $$('.main .warning').forEach(e => e.remove());
+    const main = $('.main');
+    main.insertBefore(buildWarning(err), main.firstChild);
+  }
 
   function runtimeSend(request) {
     return new Promise((resolve, reject) => {
@@ -41,15 +136,25 @@
     });
     return runtimeSend(request)
       .then(result => {
+        installed = true;
+
         $$('.warning')
           .forEach(el => el.remove());
-        $('.install').textContent = 'Installed';
         $('.install').disabled = true;
         $('.install').classList.add('installed');
         $('.set-update-url input[type=checkbox]').disabled = true;
         $('.set-update-url').title = result.updateUrl ?
           t('installUpdateFrom', result.updateUrl) : '';
-        window.dispatchEvent(new CustomEvent('installed', {detail: result}));
+
+        updateMeta(result);
+
+        if (liveReload) {
+          port.postMessage({method: 'liveReloadStart'});
+        }
+        $('.live-reload').addEventListener('change', () => {
+          const method = 'liveReload' + (liveReload ? 'Start' : 'Stop');
+          port.postMessage({method});
+        });
       })
       .catch(err => {
         alert(chrome.i18n.getMessage('styleInstallFailed', String(err)));
@@ -81,6 +186,8 @@
     const dupData = dup && dup.usercssData;
     const versionTest = dup && semverCompare(data.version, dupData.version);
 
+    updateMeta(style, dup);
+
     // update UI
     if (versionTest < 0) {
       $('.actions').parentNode.insertBefore(
@@ -120,59 +227,14 @@
       }
     };
 
-    // update editor
-    cm.setPreprocessor(data.preprocessor);
-
-    // update metas
-    document.title = `${installButtonLabel()} ${data.name}`;
-
-    $('.install').textContent = installButtonLabel();
-    $('.set-update-url').title = dup && dup.updateUrl && t('installUpdateFrom', dup.updateUrl) || '';
-    $('.meta-name').textContent = data.name;
-    $('.meta-version').textContent = data.version;
-    $('.meta-description').textContent = data.description;
-
-    if (data.author) {
-      $('.meta-author').textContent = data.author;
+    // live reload
+    const setLiveReload = $('.live-reload input[type=checkbox]');
+    if (updateUrl.protocol !== 'file:') {
+      setLiveReload.parentNode.remove();
     } else {
-      $('.meta-author').parentNode.remove();
-    }
-    if (data.license) {
-      $('.meta-license').textContent = data.license;
-    } else {
-      $('.meta-license').parentNode.remove();
-    }
-
-    getAppliesTo(style).forEach(pattern =>
-      $('.applies-to').appendChild($element({tag: 'li', textContent: pattern}))
-    );
-
-    const externalLink = makeExternalLink();
-    if (externalLink) {
-      $('.external-link').appendChild(externalLink);
-    }
-
-    function makeExternalLink() {
-      const urls = [];
-      if (data.homepageURL) {
-        urls.push([data.homepageURL, t('externalHomepage')]);
-      }
-      if (data.supportURL) {
-        urls.push([data.supportURL, t('externalSupport')]);
-      }
-      if (urls.length) {
-        return $element({appendChild: [
-          $element({tag: 'h3', textContent: t('externalLink')}),
-          $element({tag: 'ul', appendChild: urls.map(args =>
-            $element({tag: 'li', appendChild: makeLink(...args)})
-          )})
-        ]});
-      }
-    }
-
-    function installButtonLabel() {
-      return t(!dup ? 'installButton' :
-        versionTest > 0 ? 'installButtonUpdate' : 'installButtonReinstall');
+      setLiveReload.addEventListener('change', () => {
+        liveReload = setLiveReload.checked;
+      });
     }
   }