diff --git a/Tests/LibWeb/Ref/expected/border-radius-shrink-zero-sized-box-ref.html b/Tests/LibWeb/Ref/expected/border-radius-shrink-zero-sized-box-ref.html
index d1a487a5168..8d9c7bda665 100644
--- a/Tests/LibWeb/Ref/expected/border-radius-shrink-zero-sized-box-ref.html
+++ b/Tests/LibWeb/Ref/expected/border-radius-shrink-zero-sized-box-ref.html
@@ -1 +1,2 @@
+<!DOCTYPE html>
 <!-- This page is intentionally left blank. -->
diff --git a/Tests/LibWeb/Ref/expected/css-any-link-selector-ref.html b/Tests/LibWeb/Ref/expected/css-any-link-selector-ref.html
index c52dc9d82a3..2cc7b6217a6 100644
--- a/Tests/LibWeb/Ref/expected/css-any-link-selector-ref.html
+++ b/Tests/LibWeb/Ref/expected/css-any-link-selector-ref.html
@@ -1 +1,2 @@
+<!DOCTYPE html>
 <a href="example.com" style="color: orange">Link</a>
diff --git a/Tests/LibWeb/Ref/expected/css-gradient-currentcolor-ref.html b/Tests/LibWeb/Ref/expected/css-gradient-currentcolor-ref.html
index 1f0ebff8b2e..406804f8ea0 100644
--- a/Tests/LibWeb/Ref/expected/css-gradient-currentcolor-ref.html
+++ b/Tests/LibWeb/Ref/expected/css-gradient-currentcolor-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <html>
 <style>
     div {
diff --git a/Tests/LibWeb/Ref/expected/css-has-compound.html b/Tests/LibWeb/Ref/expected/css-has-compound.html
index 3cd0106af38..95e62c23b37 100644
--- a/Tests/LibWeb/Ref/expected/css-has-compound.html
+++ b/Tests/LibWeb/Ref/expected/css-has-compound.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <a href="https://example.com" style="color: orange"><em><span class="nice"><em>Link</em></span></em></a>
 <a href="https://example.com"><em>Link</em></a>
 <a href="https://example.com"><em><span class="hello"><em>Link</em></span></em></a>
diff --git a/Tests/LibWeb/Ref/expected/css-has-descendant.html b/Tests/LibWeb/Ref/expected/css-has-descendant.html
index 1a4ec55270c..b64debe306f 100644
--- a/Tests/LibWeb/Ref/expected/css-has-descendant.html
+++ b/Tests/LibWeb/Ref/expected/css-has-descendant.html
@@ -1,2 +1,3 @@
+<!DOCTYPE html>
 <a href="https://example.com" style="color: orange"><em><span class="nice"><em>Link</em></span></em></a>
 <a href="https://example.com"><em>Link</em></a>
diff --git a/Tests/LibWeb/Ref/expected/css-has-direct-child.html b/Tests/LibWeb/Ref/expected/css-has-direct-child.html
index 1cf696d2f2c..dd91a85fe2c 100644
--- a/Tests/LibWeb/Ref/expected/css-has-direct-child.html
+++ b/Tests/LibWeb/Ref/expected/css-has-direct-child.html
@@ -1,2 +1,3 @@
+<!DOCTYPE html>
 <a href="https://example.com" style="color: orange"><span>Link</span></a>
 <a href="https://example.com"><em><span>Link</span></em></a>
diff --git a/Tests/LibWeb/Ref/expected/css-has-next-sibling.html b/Tests/LibWeb/Ref/expected/css-has-next-sibling.html
index 85ee3493a20..dc1b7c9ee0f 100644
--- a/Tests/LibWeb/Ref/expected/css-has-next-sibling.html
+++ b/Tests/LibWeb/Ref/expected/css-has-next-sibling.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <a href="https://example.com" style="color: orange">Link</a><span>Hello!</span>
 <a href="https://example.com">Link</a><em>Hello!</em>
 <a href="https://example.com">Link</a><em>Hello</em><span>world!</span>
diff --git a/Tests/LibWeb/Ref/expected/css-has-subsequent-sibling.html b/Tests/LibWeb/Ref/expected/css-has-subsequent-sibling.html
index 744d14a8115..dc3988ae600 100644
--- a/Tests/LibWeb/Ref/expected/css-has-subsequent-sibling.html
+++ b/Tests/LibWeb/Ref/expected/css-has-subsequent-sibling.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <div>
     <a href="https://example.com" style="color: orange">Link</a><span>Hello!</span>
 </div>
diff --git a/Tests/LibWeb/Ref/expected/css-lang-selector-ref.html b/Tests/LibWeb/Ref/expected/css-lang-selector-ref.html
index a6ae6f7831b..8483dd5add7 100644
--- a/Tests/LibWeb/Ref/expected/css-lang-selector-ref.html
+++ b/Tests/LibWeb/Ref/expected/css-lang-selector-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <html lang="en">
 <style>
     div {
diff --git a/Tests/LibWeb/Ref/expected/css-local-link-selector-ref.html b/Tests/LibWeb/Ref/expected/css-local-link-selector-ref.html
index 44d033ca803..b87b81168f6 100644
--- a/Tests/LibWeb/Ref/expected/css-local-link-selector-ref.html
+++ b/Tests/LibWeb/Ref/expected/css-local-link-selector-ref.html
@@ -1,2 +1,3 @@
+<!DOCTYPE html>
 <a href="" style="color: orange">Local</a>
 <a href="example.com">Not local</a>
diff --git a/Tests/LibWeb/Ref/expected/css-nested-has.html b/Tests/LibWeb/Ref/expected/css-nested-has.html
index 48f04cc05fa..8ae839f8d5b 100644
--- a/Tests/LibWeb/Ref/expected/css-nested-has.html
+++ b/Tests/LibWeb/Ref/expected/css-nested-has.html
@@ -1 +1,2 @@
+<!DOCTYPE html>
 <a href="https://example.com"><em><span><strong>Link</strong></span></em></a>
diff --git a/Tests/LibWeb/Ref/expected/css-placeholder-shown-selector-ref.html b/Tests/LibWeb/Ref/expected/css-placeholder-shown-selector-ref.html
index e04d3fb7349..94a9bd315f8 100644
--- a/Tests/LibWeb/Ref/expected/css-placeholder-shown-selector-ref.html
+++ b/Tests/LibWeb/Ref/expected/css-placeholder-shown-selector-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style>
 .placeholder-shown {
     background-color: yellow;
diff --git a/Tests/LibWeb/Ref/expected/css-pseudo-element-in-has.html b/Tests/LibWeb/Ref/expected/css-pseudo-element-in-has.html
index 7eee20c6ad3..269d5ed3303 100644
--- a/Tests/LibWeb/Ref/expected/css-pseudo-element-in-has.html
+++ b/Tests/LibWeb/Ref/expected/css-pseudo-element-in-has.html
@@ -1 +1,2 @@
+<!DOCTYPE html>
 <a href="https://example.com"><span>foo<span style="color: red">bar</span></span></a>
diff --git a/Tests/LibWeb/Ref/expected/css-read-only-read-write-selectors-ref.html b/Tests/LibWeb/Ref/expected/css-read-only-read-write-selectors-ref.html
index a01bac2daf5..59e7af2a3d3 100644
--- a/Tests/LibWeb/Ref/expected/css-read-only-read-write-selectors-ref.html
+++ b/Tests/LibWeb/Ref/expected/css-read-only-read-write-selectors-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style>
     .read-write {
         background-color: green;
diff --git a/Tests/LibWeb/Ref/expected/inline-stacking-context-ref.html b/Tests/LibWeb/Ref/expected/inline-stacking-context-ref.html
index d9a54c53375..4a160f73404 100644
--- a/Tests/LibWeb/Ref/expected/inline-stacking-context-ref.html
+++ b/Tests/LibWeb/Ref/expected/inline-stacking-context-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style>
 #text {
     z-index: 10;
diff --git a/Tests/LibWeb/Ref/expected/inline-visibility-hidden-ref.html b/Tests/LibWeb/Ref/expected/inline-visibility-hidden-ref.html
index 60a090765ab..5a328351b49 100644
--- a/Tests/LibWeb/Ref/expected/inline-visibility-hidden-ref.html
+++ b/Tests/LibWeb/Ref/expected/inline-visibility-hidden-ref.html
@@ -1 +1,2 @@
+<!DOCTYPE html>
 <span>hello friends</span>
diff --git a/Tests/LibWeb/Ref/expected/nested-svg-as-img-ref.html b/Tests/LibWeb/Ref/expected/nested-svg-as-img-ref.html
index e6e304f081c..19dac361fcc 100644
--- a/Tests/LibWeb/Ref/expected/nested-svg-as-img-ref.html
+++ b/Tests/LibWeb/Ref/expected/nested-svg-as-img-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <svg width="22" height="22" xmlns="http://www.w3.org/2000/svg">
   <rect x="5" y="5" width="12" height="12" fill="red" />
 </svg>
diff --git a/Tests/LibWeb/Ref/expected/options-set-index.html b/Tests/LibWeb/Ref/expected/options-set-index.html
index f2530448d2d..90bfac1c8a8 100644
--- a/Tests/LibWeb/Ref/expected/options-set-index.html
+++ b/Tests/LibWeb/Ref/expected/options-set-index.html
@@ -1 +1,2 @@
+<!DOCTYPE html>
 <select><option>text</option></select>
diff --git a/Tests/LibWeb/Ref/expected/positioned-elements-in-scroll-container-ref.html b/Tests/LibWeb/Ref/expected/positioned-elements-in-scroll-container-ref.html
index 42f46bc0140..30fe6b1960a 100644
--- a/Tests/LibWeb/Ref/expected/positioned-elements-in-scroll-container-ref.html
+++ b/Tests/LibWeb/Ref/expected/positioned-elements-in-scroll-container-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <html>
 <link rel="match" href="../expected/positioned-elements-in-scroll-container-ref.html" />
 <style>
diff --git a/Tests/LibWeb/Ref/expected/scrollable-box-with-nested-stacking-context-ref.html b/Tests/LibWeb/Ref/expected/scrollable-box-with-nested-stacking-context-ref.html
index 8f2863a4337..5379ced67cd 100644
--- a/Tests/LibWeb/Ref/expected/scrollable-box-with-nested-stacking-context-ref.html
+++ b/Tests/LibWeb/Ref/expected/scrollable-box-with-nested-stacking-context-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style>
     * {
         scrollbar-width: none;
diff --git a/Tests/LibWeb/Ref/expected/scrollable-overflow-viewport-bug.html b/Tests/LibWeb/Ref/expected/scrollable-overflow-viewport-bug.html
index 04ce6d96c5f..1c3a7f6b9f7 100644
--- a/Tests/LibWeb/Ref/expected/scrollable-overflow-viewport-bug.html
+++ b/Tests/LibWeb/Ref/expected/scrollable-overflow-viewport-bug.html
@@ -1 +1,2 @@
+<!DOCTYPE html>
 <!-- This page intentionally left blank -->
diff --git a/Tests/LibWeb/Ref/expected/separate-borders-ref.html b/Tests/LibWeb/Ref/expected/separate-borders-ref.html
index 717f118bd11..7fbcba64e10 100644
--- a/Tests/LibWeb/Ref/expected/separate-borders-ref.html
+++ b/Tests/LibWeb/Ref/expected/separate-borders-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style type="text/css">
     td {
         border: 5px solid blue;
diff --git a/Tests/LibWeb/Ref/expected/simple-svg-mask-ref.html b/Tests/LibWeb/Ref/expected/simple-svg-mask-ref.html
index dcdc1df6253..e9d87b266be 100644
--- a/Tests/LibWeb/Ref/expected/simple-svg-mask-ref.html
+++ b/Tests/LibWeb/Ref/expected/simple-svg-mask-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <svg width="120" viewBox="-10 -10 120 120">
   <rect x="-10" y="-10" width="120" height="120" fill="blue" />
   <rect x="50" y="10" width="40" height="80" fill="red"  />
diff --git a/Tests/LibWeb/Ref/expected/square-ref.html b/Tests/LibWeb/Ref/expected/square-ref.html
index 4f1f9eec268..bbcfa2d5c73 100644
--- a/Tests/LibWeb/Ref/expected/square-ref.html
+++ b/Tests/LibWeb/Ref/expected/square-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style>
     .box {
         width: 100px;
diff --git a/Tests/LibWeb/Ref/expected/sticky-box-with-percentage-insets-ref.html b/Tests/LibWeb/Ref/expected/sticky-box-with-percentage-insets-ref.html
index 725c217f396..3419d6ea886 100644
--- a/Tests/LibWeb/Ref/expected/sticky-box-with-percentage-insets-ref.html
+++ b/Tests/LibWeb/Ref/expected/sticky-box-with-percentage-insets-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style>
     * {
         scrollbar-width: 0;
diff --git a/Tests/LibWeb/Ref/expected/sticky-positioned-box-with-border-ref.html b/Tests/LibWeb/Ref/expected/sticky-positioned-box-with-border-ref.html
index b74173708f5..20d98462d47 100644
--- a/Tests/LibWeb/Ref/expected/sticky-positioned-box-with-border-ref.html
+++ b/Tests/LibWeb/Ref/expected/sticky-positioned-box-with-border-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="reference/sticky-positioned-box-with-border-ref.html" />
 <style>
     * {
diff --git a/Tests/LibWeb/Ref/expected/svg-clipPathUnits.html b/Tests/LibWeb/Ref/expected/svg-clipPathUnits.html
index 6214c901ca9..b980689026c 100644
--- a/Tests/LibWeb/Ref/expected/svg-clipPathUnits.html
+++ b/Tests/LibWeb/Ref/expected/svg-clipPathUnits.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <svg width="200" viewBox="0 0 100 100">
   <link rel="match" href="../expected/svg-maskContentUnits-ref.html" />
   <clipPath id="myClip1" clipPathUnits="userSpaceOnUse">
diff --git a/Tests/LibWeb/Ref/expected/svg-display-attr.html b/Tests/LibWeb/Ref/expected/svg-display-attr.html
index 366ce5d2d97..bfcdeda6815 100644
--- a/Tests/LibWeb/Ref/expected/svg-display-attr.html
+++ b/Tests/LibWeb/Ref/expected/svg-display-attr.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <svg width="120" viewBox="0 0 100 100">
 	<circle cx="25" cy="25" fill="blue" r="25" />
     <g><circle cx="75" cy="25" fill="red" r="25" /></g>
diff --git a/Tests/LibWeb/Ref/expected/svg-file-matches-html-file.html b/Tests/LibWeb/Ref/expected/svg-file-matches-html-file.html
index ca773b9b333..4f2dfafadf5 100644
--- a/Tests/LibWeb/Ref/expected/svg-file-matches-html-file.html
+++ b/Tests/LibWeb/Ref/expected/svg-file-matches-html-file.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style>
   * {
     margin: 0;
diff --git a/Tests/LibWeb/Ref/expected/svg-overflow-hidden-ref.html b/Tests/LibWeb/Ref/expected/svg-overflow-hidden-ref.html
index af93097d4b4..a3a2c9e6252 100644
--- a/Tests/LibWeb/Ref/expected/svg-overflow-hidden-ref.html
+++ b/Tests/LibWeb/Ref/expected/svg-overflow-hidden-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style>
     svg { 
         height: 200px;
diff --git a/Tests/LibWeb/Ref/expected/svg-overflow-visible-ref.html b/Tests/LibWeb/Ref/expected/svg-overflow-visible-ref.html
index cd82def5f4b..5fe821ef7fa 100644
--- a/Tests/LibWeb/Ref/expected/svg-overflow-visible-ref.html
+++ b/Tests/LibWeb/Ref/expected/svg-overflow-visible-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style>
     svg { 
         height: 200px;
diff --git a/Tests/LibWeb/Ref/expected/svg-symbol-ref.html b/Tests/LibWeb/Ref/expected/svg-symbol-ref.html
index c89ff115495..a8d66e6a0cd 100644
--- a/Tests/LibWeb/Ref/expected/svg-symbol-ref.html
+++ b/Tests/LibWeb/Ref/expected/svg-symbol-ref.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <svg><symbol fill="green" id="dot" width="500" height="500" viewBox="0 0 2 10">
 <circle cx="1" cy="1" r="1"/>
 <circle fill="blue" cx="1.5" cy="1" r="1"/>
diff --git a/Tests/LibWeb/Ref/expected/webkit-text-fill-color.html b/Tests/LibWeb/Ref/expected/webkit-text-fill-color.html
index 91529b23845..b2d4797d94a 100644
--- a/Tests/LibWeb/Ref/expected/webkit-text-fill-color.html
+++ b/Tests/LibWeb/Ref/expected/webkit-text-fill-color.html
@@ -1 +1,2 @@
+<!DOCTYPE html>
 <p style="color: lime; text-decoration: underline black;">Well, hello friends!</p>
diff --git a/Tests/LibWeb/Ref/expected/zero-area-child-creating-scrollable-overflow.html b/Tests/LibWeb/Ref/expected/zero-area-child-creating-scrollable-overflow.html
index d1a487a5168..8d9c7bda665 100644
--- a/Tests/LibWeb/Ref/expected/zero-area-child-creating-scrollable-overflow.html
+++ b/Tests/LibWeb/Ref/expected/zero-area-child-creating-scrollable-overflow.html
@@ -1 +1,2 @@
+<!DOCTYPE html>
 <!-- This page is intentionally left blank. -->
diff --git a/Tests/LibWeb/Ref/input/border-radius-shrink-zero-sized-box.html b/Tests/LibWeb/Ref/input/border-radius-shrink-zero-sized-box.html
index 4a439a5d0ad..e9d8a4cc10c 100644
--- a/Tests/LibWeb/Ref/input/border-radius-shrink-zero-sized-box.html
+++ b/Tests/LibWeb/Ref/input/border-radius-shrink-zero-sized-box.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/border-radius-shrink-zero-sized-box-ref.html" />
 <style>
   #test {
diff --git a/Tests/LibWeb/Ref/input/css-any-link-selector.html b/Tests/LibWeb/Ref/input/css-any-link-selector.html
index dd9a1fdca1d..fe84bc99996 100644
--- a/Tests/LibWeb/Ref/input/css-any-link-selector.html
+++ b/Tests/LibWeb/Ref/input/css-any-link-selector.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/css-any-link-selector-ref.html" />
 <style>
     :any-link {
diff --git a/Tests/LibWeb/Ref/input/css-gradient-currentcolor.html b/Tests/LibWeb/Ref/input/css-gradient-currentcolor.html
index 12695b5e9b3..645a794fc1a 100644
--- a/Tests/LibWeb/Ref/input/css-gradient-currentcolor.html
+++ b/Tests/LibWeb/Ref/input/css-gradient-currentcolor.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <html>
 <link rel="match" href="../expected/css-gradient-currentcolor-ref.html" />
 <style>
diff --git a/Tests/LibWeb/Ref/input/css-lang-selector.html b/Tests/LibWeb/Ref/input/css-lang-selector.html
index 8a3aaa9227f..96b27952e0f 100644
--- a/Tests/LibWeb/Ref/input/css-lang-selector.html
+++ b/Tests/LibWeb/Ref/input/css-lang-selector.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <html lang="en">
 <link rel="match" href="../expected/css-lang-selector-ref.html" />
 <style>
diff --git a/Tests/LibWeb/Ref/input/css-local-link-selector.html b/Tests/LibWeb/Ref/input/css-local-link-selector.html
index 7773ea25b18..cd8ba942a5f 100644
--- a/Tests/LibWeb/Ref/input/css-local-link-selector.html
+++ b/Tests/LibWeb/Ref/input/css-local-link-selector.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/css-local-link-selector-ref.html" />
 <style>
     :local-link {
diff --git a/Tests/LibWeb/Ref/input/css-placeholder-shown-selector.html b/Tests/LibWeb/Ref/input/css-placeholder-shown-selector.html
index 32fcc461f4d..29f6ddb190a 100644
--- a/Tests/LibWeb/Ref/input/css-placeholder-shown-selector.html
+++ b/Tests/LibWeb/Ref/input/css-placeholder-shown-selector.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/css-placeholder-shown-selector-ref.html" />
 <style>
 :placeholder-shown {
diff --git a/Tests/LibWeb/Ref/input/css-read-only-read-write-selectors.html b/Tests/LibWeb/Ref/input/css-read-only-read-write-selectors.html
index e524992d6b8..a0e09828939 100644
--- a/Tests/LibWeb/Ref/input/css-read-only-read-write-selectors.html
+++ b/Tests/LibWeb/Ref/input/css-read-only-read-write-selectors.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/css-read-only-read-write-selectors-ref.html" />
 <style>
     body :read-write {
diff --git a/Tests/LibWeb/Ref/input/inline-stacking-context.html b/Tests/LibWeb/Ref/input/inline-stacking-context.html
index 9e4b987df0d..21f96d048c1 100644
--- a/Tests/LibWeb/Ref/input/inline-stacking-context.html
+++ b/Tests/LibWeb/Ref/input/inline-stacking-context.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/inline-stacking-context-ref.html" /><style>
 span {
     z-index: 10;
diff --git a/Tests/LibWeb/Ref/input/inline-visibility-hidden.html b/Tests/LibWeb/Ref/input/inline-visibility-hidden.html
index fa6a463a687..5b1b573702d 100644
--- a/Tests/LibWeb/Ref/input/inline-visibility-hidden.html
+++ b/Tests/LibWeb/Ref/input/inline-visibility-hidden.html
@@ -1,2 +1,3 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/inline-visibility-hidden-ref.html" />
 <span>hello friends<span style="visibility: hidden"> and enemies</span></span>
diff --git a/Tests/LibWeb/Ref/input/nested-svg-as-img.html b/Tests/LibWeb/Ref/input/nested-svg-as-img.html
index af2b6318a23..f9e7d726b46 100644
--- a/Tests/LibWeb/Ref/input/nested-svg-as-img.html
+++ b/Tests/LibWeb/Ref/input/nested-svg-as-img.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <style>
   img { border: 1px solid black; }
  </style>
diff --git a/Tests/LibWeb/Ref/input/options-set-index.html b/Tests/LibWeb/Ref/input/options-set-index.html
index 4cd3b17bc84..e5f22ed82cc 100644
--- a/Tests/LibWeb/Ref/input/options-set-index.html
+++ b/Tests/LibWeb/Ref/input/options-set-index.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/options-set-index.html" />
 <select id="select"></select>
 <script>
diff --git a/Tests/LibWeb/Ref/input/positioned-elements-in-scroll-container.html b/Tests/LibWeb/Ref/input/positioned-elements-in-scroll-container.html
index 38a2de1cf1d..08c37de88d2 100644
--- a/Tests/LibWeb/Ref/input/positioned-elements-in-scroll-container.html
+++ b/Tests/LibWeb/Ref/input/positioned-elements-in-scroll-container.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <html>
 <link rel="match" href="../expected/positioned-elements-in-scroll-container-ref.html" />
 <style>
diff --git a/Tests/LibWeb/Ref/input/scrollable-box-with-nested-stacking-context.html b/Tests/LibWeb/Ref/input/scrollable-box-with-nested-stacking-context.html
index bc1050b4afc..96a19fe0e5b 100644
--- a/Tests/LibWeb/Ref/input/scrollable-box-with-nested-stacking-context.html
+++ b/Tests/LibWeb/Ref/input/scrollable-box-with-nested-stacking-context.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/scrollable-box-with-nested-stacking-context-ref.html" />
 <style>
     * {
diff --git a/Tests/LibWeb/Ref/input/separate-borders-inline-table.html b/Tests/LibWeb/Ref/input/separate-borders-inline-table.html
index 697c584fd61..5d1fae66187 100644
--- a/Tests/LibWeb/Ref/input/separate-borders-inline-table.html
+++ b/Tests/LibWeb/Ref/input/separate-borders-inline-table.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/separate-borders-ref.html" />
 <style type="text/css">
     td {
diff --git a/Tests/LibWeb/Ref/input/simple-svg-mask.html b/Tests/LibWeb/Ref/input/simple-svg-mask.html
index f2b3f1f79fc..26adfcccf24 100644
--- a/Tests/LibWeb/Ref/input/simple-svg-mask.html
+++ b/Tests/LibWeb/Ref/input/simple-svg-mask.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/simple-svg-mask-ref.html" />
 <svg width="120" viewBox="-10 -10 120 120">
   <mask id="myMask">
diff --git a/Tests/LibWeb/Ref/input/square-flex.html b/Tests/LibWeb/Ref/input/square-flex.html
index 9857e946441..173e9592bc1 100644
--- a/Tests/LibWeb/Ref/input/square-flex.html
+++ b/Tests/LibWeb/Ref/input/square-flex.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/square-ref.html" />
 <style>
     .box {
diff --git a/Tests/LibWeb/Ref/input/sticky-box-with-percentage-insets.html b/Tests/LibWeb/Ref/input/sticky-box-with-percentage-insets.html
index ddad8a31734..8bd27ddb831 100644
--- a/Tests/LibWeb/Ref/input/sticky-box-with-percentage-insets.html
+++ b/Tests/LibWeb/Ref/input/sticky-box-with-percentage-insets.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/sticky-box-with-percentage-insets-ref.html" />
 <style>
     * {
diff --git a/Tests/LibWeb/Ref/input/sticky-positioned-box-with-border.html b/Tests/LibWeb/Ref/input/sticky-positioned-box-with-border.html
index 00d325799bf..e0c095bace2 100644
--- a/Tests/LibWeb/Ref/input/sticky-positioned-box-with-border.html
+++ b/Tests/LibWeb/Ref/input/sticky-positioned-box-with-border.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/sticky-positioned-box-with-border-ref.html" />
 <style>
     * {
diff --git a/Tests/LibWeb/Ref/input/svg-alpha-mask-attribute.html b/Tests/LibWeb/Ref/input/svg-alpha-mask-attribute.html
index d65fe30574f..36e4b359cd2 100644
--- a/Tests/LibWeb/Ref/input/svg-alpha-mask-attribute.html
+++ b/Tests/LibWeb/Ref/input/svg-alpha-mask-attribute.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/simple-svg-mask-ref.html" />
 <svg width="120" viewBox="-10 -10 120 120">
   <defs>
diff --git a/Tests/LibWeb/Ref/input/svg-alpha-mask.html b/Tests/LibWeb/Ref/input/svg-alpha-mask.html
index fa93cab15d1..865095acf9c 100644
--- a/Tests/LibWeb/Ref/input/svg-alpha-mask.html
+++ b/Tests/LibWeb/Ref/input/svg-alpha-mask.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/simple-svg-mask-ref.html" />
 <svg width="120" viewBox="-10 -10 120 120">
   <defs>
diff --git a/Tests/LibWeb/Ref/input/svg-display-attr.html b/Tests/LibWeb/Ref/input/svg-display-attr.html
index 662f50b8324..5bb88ec7045 100644
--- a/Tests/LibWeb/Ref/input/svg-display-attr.html
+++ b/Tests/LibWeb/Ref/input/svg-display-attr.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/svg-display-attr.html" />
 <svg width="120" viewBox="0 0 100 100">
 	<circle cx="25" cy="25" fill="blue" r="25" />
diff --git a/Tests/LibWeb/Ref/input/svg-mask-in-defs.html b/Tests/LibWeb/Ref/input/svg-mask-in-defs.html
index 0b847f614f6..100ff0620c4 100644
--- a/Tests/LibWeb/Ref/input/svg-mask-in-defs.html
+++ b/Tests/LibWeb/Ref/input/svg-mask-in-defs.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/simple-svg-mask-ref.html" />
 <svg width="120" viewBox="-10 -10 120 120">
   <defs>
diff --git a/Tests/LibWeb/Ref/input/svg-mask-maskUnits-userSpaceOnUse.html b/Tests/LibWeb/Ref/input/svg-mask-maskUnits-userSpaceOnUse.html
index a490f5d3fa3..d77bac0dc02 100644
--- a/Tests/LibWeb/Ref/input/svg-mask-maskUnits-userSpaceOnUse.html
+++ b/Tests/LibWeb/Ref/input/svg-mask-maskUnits-userSpaceOnUse.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/simple-svg-mask-ref.html" />
 <svg width="120" viewBox="-10 -10 120 120">
   <defs>
diff --git a/Tests/LibWeb/Ref/input/svg-overflow-hidden.html b/Tests/LibWeb/Ref/input/svg-overflow-hidden.html
index f2de1f078bb..3aaa3120954 100644
--- a/Tests/LibWeb/Ref/input/svg-overflow-hidden.html
+++ b/Tests/LibWeb/Ref/input/svg-overflow-hidden.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/svg-overflow-hidden-ref.html" />
 <style>
     svg { 
diff --git a/Tests/LibWeb/Ref/input/svg-overflow-visible.html b/Tests/LibWeb/Ref/input/svg-overflow-visible.html
index 8fa22221eb2..095632e28da 100644
--- a/Tests/LibWeb/Ref/input/svg-overflow-visible.html
+++ b/Tests/LibWeb/Ref/input/svg-overflow-visible.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/svg-overflow-visible-ref.html" />
 <style>
     svg { 
diff --git a/Tests/LibWeb/Ref/input/svg-symbol.html b/Tests/LibWeb/Ref/input/svg-symbol.html
index c65cd2d8bbb..224227ccb6b 100644
--- a/Tests/LibWeb/Ref/input/svg-symbol.html
+++ b/Tests/LibWeb/Ref/input/svg-symbol.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/svg-symbol-ref.html" />
 <svg><symbol id="dot" width="500" height="500" viewBox="0 0 2 10">
 <circle fill="green" cx="1" cy="1" r="1"/>
diff --git a/Tests/LibWeb/Ref/input/svg-text-crash.html b/Tests/LibWeb/Ref/input/svg-text-crash.html
index 5e409546230..5e1b131b8d0 100644
--- a/Tests/LibWeb/Ref/input/svg-text-crash.html
+++ b/Tests/LibWeb/Ref/input/svg-text-crash.html
@@ -1,3 +1,4 @@
+<!DOCTYPE html>
 <!-- matches against itself because the only thing being tested is that this does not crash. -->
 <link rel="match" href="./svg-text-crash.html" />
 <svg>
diff --git a/Tests/LibWeb/Ref/input/webkit-text-fill-color.html b/Tests/LibWeb/Ref/input/webkit-text-fill-color.html
index b8654714ea0..4fe69f8bb04 100644
--- a/Tests/LibWeb/Ref/input/webkit-text-fill-color.html
+++ b/Tests/LibWeb/Ref/input/webkit-text-fill-color.html
@@ -1,2 +1,3 @@
+<!DOCTYPE html>
 <link rel="match" href="../expected/webkit-text-fill-color.html" />
 <p style="text-decoration: underline; -webkit-text-fill-color: lime">Well, hello friends!</p>
