diff --git a/Shared/Article Rendering/main.js b/Shared/Article Rendering/main.js
index 413906197..0b42889bd 100644
--- a/Shared/Article Rendering/main.js	
+++ b/Shared/Article Rendering/main.js	
@@ -18,10 +18,27 @@ function stripStylesFromElement(element, propertiesToStrip) {
 	}
 }
 
+// Strip inline styles that could harm readability.
 function stripStyles() {
 	document.getElementsByTagName("body")[0].querySelectorAll("style, link[rel=stylesheet]").forEach(element => element.remove());
 	// Removing "background" and "font" will also remove properties that would be reflected in them, e.g., "background-color" and "font-family"
-	document.getElementsByTagName("body")[0].querySelectorAll("[style]").forEach(element => stripStylesFromElement(element, ["color", "background", "font", "max-width", "max-height"]));
+	document.getElementsByTagName("body")[0].querySelectorAll("[style]").forEach(element => stripStylesFromElement(element, ["color", "background", "font", "max-width", "max-height", "position"]));
+}
+
+// Constrain the height of iframes whose heights are defined relative to the document body to be at most
+// 50% of the viewport width.
+function constrainBodyRelativeIframes() {
+	let iframes = document.getElementsByTagName("iframe");
+
+	for (iframe of iframes) {
+		if (iframe.offsetParent === document.body) {
+			let heightAttribute = iframe.style.height;
+
+			if (/%|vw|vh$/i.test(heightAttribute)) {
+				iframe.classList.add("nnw-constrained");
+			}
+		}
+	}
 }
 
 // Convert all Feedbin proxy images to be used as src, otherwise change image locations to be absolute if not already
@@ -29,7 +46,7 @@ function convertImgSrc() {
 	document.querySelectorAll("img").forEach(element => {
 		if (element.hasAttribute("data-canonical-src")) {
 			element.src = element.getAttribute("data-canonical-src")
-		} else if (!element.src.match(/^[a-z]+\:\/\//i)) {
+		} else if (!/^[a-z]+\:\/\//i.test(element.src)) {
 			element.src = new URL(element.src, document.baseURI).href;
 		}
 	});
@@ -136,6 +153,7 @@ function processPage() {
 	wrapTables();
 	inlineVideos();
 	stripStyles();
+	constrainBodyRelativeIframes();
 	convertImgSrc();
 	flattenPreElements();
 	styleLocalFootnotes();
diff --git a/Shared/Article Rendering/shared.css b/Shared/Article Rendering/shared.css
index 0c5705eda..fa2a5920d 100644
--- a/Shared/Article Rendering/shared.css	
+++ b/Shared/Article Rendering/shared.css	
@@ -204,6 +204,10 @@ iframe {
 	margin: 0 auto;
 }
 
+iframe.nnw-constrained {
+	max-height: 50vw;
+}
+
 figure {
 	margin-bottom: 1em;
 	margin-top: 1em;