diff --git a/compiler/apps/playground/components/Editor/Output.tsx b/compiler/apps/playground/components/Editor/Output.tsx
index 5300392c6b..0847e044c5 100644
--- a/compiler/apps/playground/components/Editor/Output.tsx
+++ b/compiler/apps/playground/components/Editor/Output.tsx
@@ -187,6 +187,21 @@ function Output({ store, compilerOutput }: Props) {
     });
   }, [store.source, compilerOutput]);
 
+  const changedPasses: Set<string> = new Set();
+  let lastResult: string = "";
+  for (const [passName, results] of compilerOutput.results) {
+    for (const result of results) {
+      let currResult = "";
+      if (result.kind === "hir" || result.kind === "reactive") {
+        currResult += `function ${result.fnName}\n\n${result.value}`;
+      }
+      if (currResult !== lastResult) {
+        changedPasses.add(passName);
+      }
+      lastResult = currResult;
+    }
+  }
+
   return (
     <>
       <TabbedWindow
@@ -194,6 +209,7 @@ function Output({ store, compilerOutput }: Props) {
         setTabsOpen={setTabsOpen}
         tabsOpen={tabsOpen}
         tabs={tabs}
+        changedPasses={changedPasses}
       />
       {compilerOutput.kind === "err" ? (
         <div
diff --git a/compiler/apps/playground/components/TabbedWindow.tsx b/compiler/apps/playground/components/TabbedWindow.tsx
index 624f9b4936..29d094298e 100644
--- a/compiler/apps/playground/components/TabbedWindow.tsx
+++ b/compiler/apps/playground/components/TabbedWindow.tsx
@@ -15,6 +15,7 @@ export default function TabbedWindow(props: {
   tabs: TabsRecord;
   tabsOpen: Set<string>;
   setTabsOpen: (newTab: Set<string>) => void;
+  changedPasses: Set<string>;
 }): React.ReactElement {
   if (props.tabs.size === 0) {
     return (
@@ -36,6 +37,7 @@ export default function TabbedWindow(props: {
             tabs={props.tabs}
             tabsOpen={props.tabsOpen}
             setTabsOpen={props.setTabsOpen}
+            hasChanged={props.changedPasses.has(name)}
           />
         );
       })}
@@ -48,11 +50,13 @@ function TabbedWindowItem({
   tabs,
   tabsOpen,
   setTabsOpen,
+  hasChanged,
 }: {
   name: string;
   tabs: TabsRecord;
   tabsOpen: Set<string>;
   setTabsOpen: (newTab: Set<string>) => void;
+  hasChanged: boolean;
 }): React.ReactElement {
   const isShow = tabsOpen.has(name);
 
@@ -74,7 +78,7 @@ function TabbedWindowItem({
             title="Minimize tab"
             aria-label="Minimize tab"
             onClick={toggleTabs}
-            className="p-4 duration-150 ease-in border-b cursor-pointer border-grey-200 font-medium text-secondary hover:text-link"
+            className={`p-4 duration-150 ease-in border-b cursor-pointer border-grey-200 ${hasChanged ? 'font-bold' : 'font-light'} text-secondary hover:text-link`}
           >
             - {name}
           </h2>
@@ -87,7 +91,7 @@ function TabbedWindowItem({
             aria-label={`Expand compiler tab: ${name}`}
             style={{ transform: "rotate(90deg) translate(-50%)" }}
             onClick={toggleTabs}
-            className="flex-grow-0 w-5 transition-colors duration-150 ease-in font-medium text-secondary hover:text-link"
+            className={`flex-grow-0 w-5 transition-colors duration-150 ease-in ${hasChanged ? 'font-bold' : 'font-light'} text-secondary hover:text-link`}
           >
             {name}
           </button>