diff --git a/src/api/crawler.ts b/src/api/crawler.ts
index 6dfdae4..7dc5e56 100644
--- a/src/api/crawler.ts
+++ b/src/api/crawler.ts
@@ -15,7 +15,7 @@ import { Defer } from 'civkit/defer';
 import { retryWith } from 'civkit/decorators';
 import { FancyFile } from 'civkit/fancy-file';
 
-import { CONTENT_FORMAT, CrawlerOptions, CrawlerOptionsHeaderOnly, ENGINE_TYPE } from '../dto/crawler-options';
+import { CONTENT_FORMAT, CrawlerOptions, CrawlerOptionsHeaderOnly, ENGINE_TYPE, RESPOND_TIMING } from '../dto/crawler-options';
 
 import { Crawled } from '../db/crawled';
 import { DomainBlockade } from '../db/domain-blockade';
@@ -585,6 +585,7 @@ export class CrawlerHost extends RPCHost {
             url: urlToCrawl.toString(),
             createdAt: nowDate,
             expireAt: new Date(nowDate.valueOf() + this.cacheRetentionMs),
+            htmlModifiedByJs: snapshot.htmlModifiedByJs,
             urlPathDigest: digest,
         });
 
@@ -732,6 +733,12 @@ export class CrawlerHost extends RPCHost {
             cache = await this.queryCache(urlToCrawl, cacheTolerance);
         }
 
+        if (cache?.htmlModifiedByJs === false) {
+            if (crawlerOpts) {
+                crawlerOpts.respondTiming ??= RESPOND_TIMING.HTML;
+            }
+        }
+
         if (cache?.isFresh &&
             (!crawlOpts?.favorScreenshot || (crawlOpts?.favorScreenshot && (cache.screenshotAvailable && cache.pageshotAvailable))) &&
             (_.get(cache.snapshot, 'locale') === crawlOpts?.locale)
diff --git a/src/db/crawled.ts b/src/db/crawled.ts
index 4ec64f1..ee5379f 100644
--- a/src/db/crawled.ts
+++ b/src/db/crawled.ts
@@ -21,6 +21,9 @@ export class Crawled extends FirestoreRecord {
     })
     urlPathDigest!: string;
 
+    @Prop()
+    htmlModifiedByJs?: boolean;
+
     @Prop()
     snapshot?: PageSnapshot & { screenshot: never; pageshot: never; };
 
diff --git a/src/dto/crawler-options.ts b/src/dto/crawler-options.ts
index a358a64..a33471b 100644
--- a/src/dto/crawler-options.ts
+++ b/src/dto/crawler-options.ts
@@ -584,13 +584,6 @@ export class CrawlerOptions extends AutoCastable {
         if (respondTiming) {
             instance.respondTiming ??= respondTiming as RESPOND_TIMING;
         }
-        if (instance.timeout) {
-            instance.respondTiming ??= RESPOND_TIMING.NETWORK_IDLE;
-        }
-        if (instance.respondWith.includes('shot') || instance.respondWith.includes('vlm')) {
-            instance.respondTiming ??= RESPOND_TIMING.MEDIA_IDLE;
-        }
-        instance.respondTiming ??= RESPOND_TIMING.RESOURCE_IDLE;
 
         if (instance.cacheTolerance) {
             instance.cacheTolerance = instance.cacheTolerance * 1000;
@@ -603,14 +596,29 @@ export class CrawlerOptions extends AutoCastable {
         return instance;
     }
 
+    get presumedRespondTiming() {
+        if (this.respondTiming) {
+            return this.respondTiming;
+        }
+        if (this.timeout) {
+            return RESPOND_TIMING.NETWORK_IDLE;
+        }
+        if (this.respondWith.includes('shot') || this.respondWith.includes('vlm')) {
+            return RESPOND_TIMING.MEDIA_IDLE;
+        }
+
+        return RESPOND_TIMING.RESOURCE_IDLE;
+    }
+
     isSnapshotAcceptableForEarlyResponse(snapshot: PageSnapshot) {
         if (this.waitForSelector?.length) {
             return false;
         }
-        if (this.respondTiming === RESPOND_TIMING.HTML && snapshot.html) {
+        const presumedTiming = this.presumedRespondTiming;
+        if (presumedTiming === RESPOND_TIMING.HTML && snapshot.html) {
             return true;
         }
-        if (this.respondTiming === RESPOND_TIMING.MEDIA_IDLE && snapshot.lastMediaResourceLoaded && snapshot.lastMutationIdle) {
+        if (presumedTiming === RESPOND_TIMING.MEDIA_IDLE && snapshot.lastMediaResourceLoaded && snapshot.lastMutationIdle) {
             const now = Date.now();
             if ((Math.max(snapshot.lastMediaResourceLoaded, snapshot.lastContentResourceLoaded || 0) + 500) < now) {
                 return true;
@@ -622,7 +630,7 @@ export class CrawlerOptions extends AutoCastable {
         if ((this.respondWith.includes('vlm') || this.respondWith.includes('screenshot')) && !snapshot.screenshot) {
             return false;
         }
-        if (this.respondTiming === RESPOND_TIMING.RESOURCE_IDLE && snapshot.lastContentResourceLoaded && snapshot.lastMutationIdle) {
+        if (presumedTiming === RESPOND_TIMING.RESOURCE_IDLE && snapshot.lastContentResourceLoaded && snapshot.lastMutationIdle) {
             const now = Date.now();
             if ((snapshot.lastContentResourceLoaded + 500) < now) {
                 return true;
@@ -632,10 +640,10 @@ export class CrawlerOptions extends AutoCastable {
         if (this.injectFrameScript?.length || this.injectPageScript?.length) {
             return false;
         }
-        if (this.respondTiming === RESPOND_TIMING.NETWORK_IDLE) {
+        if (presumedTiming === RESPOND_TIMING.NETWORK_IDLE) {
             return false;
         }
-        if (this.respondTiming === RESPOND_TIMING.MUTATION_IDLE && snapshot.lastMutationIdle) {
+        if (presumedTiming === RESPOND_TIMING.MUTATION_IDLE && snapshot.lastMutationIdle) {
             return true;
         }
         if (this.respondWith.includes('lm')) {
diff --git a/src/services/puppeteer.ts b/src/services/puppeteer.ts
index 6f17d8e..2f29f29 100644
--- a/src/services/puppeteer.ts
+++ b/src/services/puppeteer.ts
@@ -55,6 +55,7 @@ export interface PageSnapshot {
     href: string;
     rebase?: string;
     html: string;
+    htmlModifiedByJs?: boolean;
     shadowExpanded?: string;
     text: string;
     status?: number;
@@ -377,9 +378,11 @@ function shadowDomPresent(rootElement = document.documentElement) {
 }
 
 let lastMutationIdle = 0;
+let initialHTML;
 document.addEventListener('mutationIdle', ()=> lastMutationIdle = Date.now());
 
 function giveSnapshot(stopActiveSnapshot) {
+    initialHTML ??= document.documentElement?.outerHTML;
     if (stopActiveSnapshot) {
         window.haltSnapshot = true;
     }
@@ -395,6 +398,7 @@ function giveSnapshot(stopActiveSnapshot) {
         description: document.head?.querySelector('meta[name="description"]')?.getAttribute('content') ?? '',
         href: document.location.href,
         html: document.documentElement?.outerHTML,
+        htmlModifiedByJs: false,
         text: document.body?.innerText,
         shadowExpanded: shadowDomPresent() ? cloneAndExpandShadowRoots()?.outerHTML : undefined,
         parsed: parsed,
@@ -403,6 +407,9 @@ function giveSnapshot(stopActiveSnapshot) {
         elemCount: domAnalysis.elementCount,
         lastMutationIdle,
     };
+    if (initialHTML) {
+        r.htmlModifiedByJs = initialHTML !== r.html && !r.shadowExpanded;
+    }
     if (document.baseURI !== r.href) {
         r.rebase = document.baseURI;
     }