diff --git a/Gemfile b/Gemfile
index b60f8af0..450a5d42 100644
--- a/Gemfile
+++ b/Gemfile
@@ -28,6 +28,11 @@ group :jekyll_plugins do
   gem 'jekyll-redirect-from'
 end
 
+# Checkers and such
+group :test do
+  gem 'html-proofer'
+end
+
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
 gem 'tzinfo-data', platforms: %i[mingw mswin x64_mingw jruby]
 
diff --git a/Gemfile.lock b/Gemfile.lock
index f918b9f6..3283bdcf 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,19 +1,44 @@
 GEM
   remote: https://rubygems.org/
   specs:
+    Ascii85 (1.1.0)
     addressable (2.8.4)
       public_suffix (>= 2.0.2, < 6.0)
+    afm (0.2.2)
+    async (2.6.2)
+      console (~> 1.10)
+      fiber-annotation
+      io-event (~> 1.1)
+      timers (~> 4.1)
     colorator (1.1.0)
     concurrent-ruby (1.2.2)
+    console (1.17.2)
+      fiber-annotation
+      fiber-local
     em-websocket (0.5.3)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0)
+    ethon (0.16.0)
+      ffi (>= 1.15.0)
     eventmachine (1.2.7)
     ffi (1.15.5)
+    fiber-annotation (0.2.0)
+    fiber-local (1.0.0)
     forwardable-extended (2.6.0)
+    hashery (2.1.2)
+    html-proofer (5.0.7)
+      addressable (~> 2.3)
+      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 (1.14.1)
       concurrent-ruby (~> 1.0)
+    io-event (1.2.2)
     jekyll (3.9.3)
       addressable (~> 2.4)
       colorator (~> 1.0)
@@ -51,15 +76,28 @@ GEM
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
     mercenary (0.3.6)
+    mini_portile2 (2.8.2)
+    nokogiri (1.15.3)
+      mini_portile2 (~> 2.8.2)
+      racc (~> 1.4)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
+    pdf-reader (2.11.0)
+      Ascii85 (~> 1.0)
+      afm (~> 0.2.1)
+      hashery (~> 2.0)
+      ruby-rc4
+      ttfunk
     public_suffix (5.0.1)
+    racc (1.7.1)
+    rainbow (3.1.1)
     rake (13.0.6)
     rb-fsevent (0.11.2)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
     rexml (3.2.5)
     rouge (3.30.0)
+    ruby-rc4 (0.1.5)
     rubyzip (2.3.2)
     safe_yaml (1.0.5)
     sass (3.7.4)
@@ -67,12 +105,19 @@ GEM
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
+    timers (4.3.5)
+    ttfunk (1.7.0)
+    typhoeus (1.4.0)
+      ethon (>= 0.9.0)
     webrick (1.8.1)
+    yell (2.2.2)
+    zeitwerk (2.6.8)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
+  html-proofer
   jekyll (~> 3.9)
   jekyll-feed
   jekyll-redirect-from
diff --git a/Rakefile b/Rakefile
new file mode 100644
index 00000000..2b7ad803
--- /dev/null
+++ b/Rakefile
@@ -0,0 +1,17 @@
+require 'html-proofer'
+
+task :test do
+  sh "bundle exec jekyll build"
+  options = {
+    assume_extension: '.html',
+    ignore_urls: [
+      %r{^https://indico},
+      %r{^http://lhcb},
+      %r{^http://chep20},
+      'https://seal.web.cern.ch/seal/snapshot/work-packages/mathlibs/minuit/',
+      'https://drupal.star.bnl.gov/STAR/meetings/star-collaboration-meeting-september-2021/juniors-day',
+    ],
+    only_4xx: true,
+  }
+  HTMLProofer.check_directory('_site/', options).run
+end
diff --git a/_config.yml b/_config.yml
index 0a656b08..81dac308 100644
--- a/_config.yml
+++ b/_config.yml
@@ -28,7 +28,7 @@ search_enabled: true
 # Aux links for the upper right navigation
 aux_links:
   "Scikit-HEP on GitHub":
-    - "//github.com/scikit-hep"
+    - "https://github.com/scikit-hep"
 
 gh_edit_link: true
 gh_edit_link_text: "View source for this page on GitHub."
diff --git a/_data/projects/fitting/goofit.yml b/_data/projects/fitting/goofit.yml
index 19458adf..4d154d9c 100644
--- a/_data/projects/fitting/goofit.yml
+++ b/_data/projects/fitting/goofit.yml
@@ -9,7 +9,7 @@ affiliated: true
 image: /assets/images/projusers/logo_goofit.png
 image-style: height:96px;
 longdescription: |
-  [GooFit] is a powerful, fast fitting library designed to mimic the familiar syntax of [ROOT](https://root.cern.ch)'s [RooFit](http://roofit.sourceforge.net). The code and installation instructions are [available here, on GitHub][GooFit], and a description of the fitting process and API is available on [GitHub IO](https://GooFit.github.io/GooFit).
+  [GooFit] is a powerful, fast fitting library designed to mimic the familiar syntax of [ROOT](https://root.cern.ch)'s [RooFit](https://roofit.sourceforge.net). The code and installation instructions are [available here, on GitHub][GooFit], and a description of the fitting process and API is available on [GitHub IO](https://GooFit.github.io/GooFit).
 
   [GooFit]:            https://github.com/GooFit/GooFit
 badges:
diff --git a/_data/projects/manipulation/root-numpy.yml b/_data/projects/manipulation/root-numpy.yml
index 0ca03040..34d7a2ae 100644
--- a/_data/projects/manipulation/root-numpy.yml
+++ b/_data/projects/manipulation/root-numpy.yml
@@ -1,7 +1,7 @@
 name: root\_numpy
 description: Interface between ROOT and NumPy.
 url: https://github.com/scikit-hep/root_numpy
-docs: http://scikit-hep.org/root_numpy/
+docs: https://scikit-hep.org/root_numpy/
 # affiliated: set to true for affiliated packages
 deprecated: true
 # repo: only if different from url
diff --git a/_data/projects/misc/pybind11.yml b/_data/projects/misc/pybind11.yml
index cb656154..3e5e44fe 100644
--- a/_data/projects/misc/pybind11.yml
+++ b/_data/projects/misc/pybind11.yml
@@ -17,7 +17,7 @@ longdescription: |
   system, including setuptools and CMake, without adding any dependencies.
   Unlike [Cython](https://cython.readthedocs.io), there is no new language
   required - you'll just be working in vanilla C++11. Unlike
-  [SWIG](http://swig.org), you can build up your bindings one part at a time,
+  [SWIG](https://swig.org), you can build up your bindings one part at a time,
   adding Pythonizations or custom interfaces. And unlike
   [ROOT](https://root.cern) or
   [cppyy](https://cppyy.readthedocs.io/en/latest/), it creates compiled
diff --git a/pages/about/faq.md b/pages/about/faq.md
index e00fe2c2..1c688b15 100644
--- a/pages/about/faq.md
+++ b/pages/about/faq.md
@@ -31,9 +31,9 @@ of \"issues\" or files CONTRIBUTING for details on how to get involved.
 
 ## Is there support for PyPy?
 
-It\'s a nice idea. Support for [PyPy](http://pypy.org/) across the various
+It\'s a nice idea. Support for [PyPy](https://pypy.org/) across the various
 packages could be envisaged in the near future but only once the scientific
-stack based on [NumPy](http://www.numpy.org/) supports it. This being
+stack based on [NumPy](https://numpy.org/) supports it. This being
 said, certain packages do support PyPy already.
 
 ## Is there support for GPUs?
diff --git a/pages/developers/gha_wheels.md b/pages/developers/gha_wheels.md
index 4a78ad5b..7f698b28 100644
--- a/pages/developers/gha_wheels.md
+++ b/pages/developers/gha_wheels.md
@@ -4,7 +4,7 @@ title: "GHA: Binary wheels 🔗"
 permalink: /developer/gha_wheels
 nav_order: 12
 parent: Developer information
-redirect_to: https://learn.scientific-python.org/development/guides/gha-binary/
+redirect_to: https://learn.scientific-python.org/development/guides/gha-wheels/
 ---
 
 This page has moved to Scientific-Python.
diff --git a/pages/news.md b/pages/news.md
index 177b3a60..f5ff345d 100644
--- a/pages/news.md
+++ b/pages/news.md
@@ -187,7 +187,7 @@ see also the [PDF version](https://pdg.lbl.gov/2020/reviews/rpp2020-rev-online-h
 
 **April 2017:** Package `root_numpy` joined Scikit-HEP.
 
-**November 2016:** Scikit-HEP GitHub organization and <http://scikit-hep.org/> site created.
+**November 2016:** Scikit-HEP GitHub organization and <https://scikit-hep.org/> site created.
 
 **August 2016:** First discussions brainstorming the grand picture of the Scikit-HEP project.
 Eduardo Rodrigues, Jim Pivarski and others.
diff --git a/pages/projusers/projects.md b/pages/projusers/projects.md
index 779355fc..e55cd91f 100644
--- a/pages/projusers/projects.md
+++ b/pages/projusers/projects.md
@@ -90,7 +90,7 @@ the Standard Model and beyond.
 [![img-coffea]][coffea]
 
 [Coffea][] - a prototype [Analysis
-System](http://iris-hep.org/as.html) incorporating Scikit-HEP packages
+System](https://iris-hep.org/as.html) incorporating Scikit-HEP packages
 to provide a lightweight, scalable, portable, and user-friendly
 interface for columnar analysis of HEP data. Some of the sub-packages of
 Coffea may become Scikit-HEP packages as development continues.
diff --git a/pages/user/getting-in-touch.md b/pages/user/getting-in-touch.md
index 49d2241b..f5de84e2 100644
--- a/pages/user/getting-in-touch.md
+++ b/pages/user/getting-in-touch.md
@@ -33,13 +33,13 @@ which are of particular interest for general exchanges with the "Python in HEP"
 
 Forum for general matters, announcements and discussions concerning the
 Scikit-HEP project :
-[scikit-hep-forum@googlegroups.com](scikit-hep-forum@googlegroups.com).
+[scikit-hep-forum@googlegroups.com](mailto:scikit-hep-forum@googlegroups.com).
 Please go
 [here](https://groups.google.com/forum/#!forum/scikit-hep-forum) to
 subscribe.
 
 Mailing list to ping all admins at once:
-[scikit-hep-admins@googlegroups.com](scikit-hep-admins@googlegroups.com).
+[scikit-hep-admins@googlegroups.com](mailto:scikit-hep-admins@googlegroups.com).
 Note that this list is private but anyone can send an email to it
 without sign-up.
 
diff --git a/pages/user/index.md b/pages/user/index.md
index 08799e64..95468758 100644
--- a/pages/user/index.md
+++ b/pages/user/index.md
@@ -8,7 +8,7 @@ has_children: true
 
 The pages here are intended for users of the scikit-hep packages.
 
-If you're having trouble installing Python packages or using ROOT with Scikit-HEP packages, see our [Conda installation instructions](Conda installation instructions).
+If you're having trouble installing Python packages or using ROOT with Scikit-HEP packages, see our [Conda installation instructions][installing-conda].
 
 You can find more [resources here][resources], like tutorials, publications, and talks.
 
diff --git a/pages/user/resources.md b/pages/user/resources.md
index 38ee3375..869f5fbf 100644
--- a/pages/user/resources.md
+++ b/pages/user/resources.md
@@ -141,7 +141,6 @@ or related to, the Scikit-HEP project.
 - **25 July 2022:** [NSF Cyberinfrastructure for Sustained Scientific Innovation (CSSI) Principal Investigator Meeting](https://cssi-pi-community.github.io/2022-meeting/):
 
   - _Awkward Arrays: Accelerating scientific data analysis on irregularly shaped data (poster)_, Jim Pivarski
-    \[[link](https://)\]
 
 - **14 July 2022:** [SciPy 2022](https://www.scipy2022.scipy.org/):
 
@@ -504,7 +503,7 @@ or related to, the Scikit-HEP project.
   - _Python in High-Energy Physics_, Hans Dembinski
     \[[PDF]({{ site.baseurl }}{% link assets/resources/dembinski-pygamma19-2019-03-21.pdf %})\]
 
-- **15 October 2018:** [DIANA/HEP](http://www.diana-hep.org/) project
+- **15 October 2018:** [DIANA/HEP](https://www.diana-hep.org/) project
   [topical meeting](https://indico.cern.ch/event/754335/):
 
   - _I/O for uproot_, Pratyush Das
@@ -532,14 +531,14 @@ or related to, the Scikit-HEP project.
   - _Uproot: rapidly moving data from ROOT to NumPy and Pandas_, Jim
     Pivarski
 
-- **23 October 2017:** [DIANA/HEP](http://www.diana-hep.org/) project
+- **23 October 2017:** [DIANA/HEP](https://www.diana-hep.org/) project
   [topical meeting](https://indico.cern.ch/event/664968/), CERN:
 
   - _numpythia & pyjet - interfacing PYTHIA and FastJet with NumPy_,
     Noel Dawe
 
 - **11 September 2017:** project status report,
-  [DIANA/HEP](http://www.diana-hep.org/) project [topical
+  [DIANA/HEP](https://www.diana-hep.org/) project [topical
   meeting](https://indico.cern.ch/event/650630/), CERN:
 
   - _Scikit-HEP project status_, Eduardo Rodrigues
@@ -552,7 +551,7 @@ or related to, the Scikit-HEP project.
     \[[PDF]({{ site.baseurl }}{% link assets/resources/rodrigues-lhcb-2017-04-06.pdf %})\]
 
 - **27 February 2017:** first presentation of the project,
-  [DIANA/HEP](http://www.diana-hep.org/) project [topical
+  [DIANA/HEP](https://www.diana-hep.org/) project [topical
   meeting](https://indico.cern.ch/event/596272/), CERN:
   - _The Scikit-HEP project_, Eduardo Rodrigues
   - _Ostap concepts in Scikit-HEP_, Vanya Belyaev