diff --git a/Gemfile b/Gemfile
index 7ed3a16..8afb943 100644
--- a/Gemfile
+++ b/Gemfile
@@ -20,4 +20,4 @@ gem "tzinfo-data", platforms: [:mingw, :mswin, :x64_mingw, :jruby]
 # Performance-booster for watching directories on Windows
 gem "wdm", "~> 0.1.0" if Gem.win_platform?
 
-gem "html-proofer", "~> 3.18"
+gem "html-proofer", "~> 5.0"
diff --git a/Gemfile.lock b/Gemfile.lock
index f60577c..febc07e 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -18,22 +18,30 @@ GIT
 GEM
   remote: https://rubygems.org/
   specs:
+    Ascii85 (1.1.0)
     activesupport (6.1.4.6)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 1.6, < 2)
       minitest (>= 5.1)
       tzinfo (~> 2.0)
       zeitwerk (~> 2.3)
-    addressable (2.8.0)
-      public_suffix (>= 2.0.2, < 5.0)
+    addressable (2.8.1)
+      public_suffix (>= 2.0.2, < 6.0)
+    afm (0.2.2)
+    async (2.3.1)
+      console (~> 1.10)
+      io-event (~> 1.1)
+      timers (~> 4.1)
     autoprefixer-rails (10.4.2.0)
       execjs (~> 2)
     colorator (1.1.0)
     concurrent-ruby (1.1.9)
+    console (1.16.2)
+      fiber-local
     em-websocket (0.5.3)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0)
-    ethon (0.15.0)
+    ethon (0.16.0)
       ffi (>= 1.15.0)
     eventmachine (1.2.7)
     execjs (2.7.0)
@@ -41,18 +49,22 @@ GEM
       forwardable-extended (~> 2.5)
     fastimage (2.2.6)
     ffi (1.15.5)
+    fiber-local (1.0.0)
     forwardable-extended (2.6.0)
-    html-proofer (3.19.3)
+    hashery (2.1.2)
+    html-proofer (5.0.4)
       addressable (~> 2.3)
-      mercenary (~> 0.3)
-      nokogiri (~> 1.12)
-      parallel (~> 1.3)
+      async (~> 2.1)
+      nokogiri (~> 1.13)
+      pdf-reader (~> 2.11)
       rainbow (~> 3.0)
       typhoeus (~> 1.3)
       yell (~> 2.0)
+      zeitwerk (~> 2.5)
     http_parser.rb (0.8.0)
     i18n (1.10.0)
       concurrent-ruby (~> 1.0)
+    io-event (1.1.6)
     jekyll (4.2.1)
       addressable (~> 2.4)
       colorator (~> 1.0)
@@ -97,16 +109,21 @@ GEM
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
     mercenary (0.4.0)
-    mini_portile2 (2.7.1)
+    mini_portile2 (2.8.1)
     minitest (5.15.0)
-    nokogiri (1.13.1)
-      mini_portile2 (~> 2.7.0)
+    nokogiri (1.14.1)
+      mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
-    parallel (1.21.0)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    public_suffix (4.0.6)
-    racc (1.6.0)
+    pdf-reader (2.11.0)
+      Ascii85 (~> 1.0)
+      afm (~> 0.2.1)
+      hashery (~> 2.0)
+      ruby-rc4
+      ttfunk
+    public_suffix (5.0.1)
+    racc (1.6.2)
     rack (2.2.3)
     rainbow (3.1.1)
     rb-fsevent (0.11.1)
@@ -114,6 +131,7 @@ GEM
       ffi (~> 1.0)
     rexml (3.2.5)
     rouge (3.28.0)
+    ruby-rc4 (0.1.5)
     safe_yaml (1.0.5)
     sassc (2.4.0)
       ffi (~> 1.9)
@@ -122,6 +140,8 @@ GEM
       rack (> 1, < 3)
     terminal-table (2.0.0)
       unicode-display_width (~> 1.1, >= 1.1.1)
+    timers (4.3.5)
+    ttfunk (1.7.0)
     typhoeus (1.4.0)
       ethon (>= 0.9.0)
     tzinfo (2.0.4)
@@ -136,7 +156,7 @@ PLATFORMS
 DEPENDENCIES
   autoprefixer-rails
   execjs (= 2.7.0)
-  html-proofer (~> 3.18)
+  html-proofer (~> 5.0)
   jekyll (~> 4.0)
   jekyll-assets!
   jekyll-feed (~> 0.15)