diff --git a/CodebookConcertina.php b/CodebookConcertina.php
new file mode 100644
index 0000000..95c4ad2
--- /dev/null
+++ b/CodebookConcertina.php
@@ -0,0 +1,134 @@
+<?php
+/**
+ * REDCap External Module: Codebook Concertina
+ * Expand and collapse the codebook table rows for the fields of each instrument
+ * @author Luke Stevens, Murdoch Children's Research Institute
+ */
+namespace MCRI\CodebookConcertina;
+
+use ExternalModules\AbstractExternalModule;
+use REDCap;
+
+class CodebookConcertina extends AbstractExternalModule
+{
+        const DEFAULT_TEXT_SHOW = 'Expand';
+        const DEFAULT_TEXT_SHOW_ALL = 'Expand all instruments';
+        const DEFAULT_TEXT_HIDE = 'Collapse';
+        const DEFAULT_TEXT_HIDE_ALL = 'Collapse all instruments';
+        const DEFAULT_VISIBILITY = '1';
+        
+        public function redcap_every_page_top($project_id) {
+                if (isset($project_id) && intval($project_id)>0 && PAGE==='Design/data_dictionary_codebook.php') {
+                        $btnTextShow = $this->getShowButtonText();
+                        $btnTextShowAll = $this->getShowAllButtonText();
+                        $btnTextHide = $this->getHideButtonText();
+                        $btnTextHideAll = $this->getHideAllButtonText();
+                        $defaultVisibility = $this->getDefaultVisibility();
+                        // add js to page to add toggle buttons and hide/show
+                        ?>
+<script type='text/javascript'>
+    (function(window, document, $) {
+        $(document).ready(function() {
+            var defaultVisibility = <?php echo $defaultVisibility;?>;
+            var icons = ['down', 'up'];
+            var btnLbl = ['<?php echo $btnTextShow;?>', '<?php echo $btnTextHide;?>'];
+            var btnLblAll = ['<?php echo $btnTextShowAll;?>', '<?php echo $btnTextHideAll;?>'];
+            var currentForm = '';
+
+            function btnLblText(visibility) {
+                return '<span class="glyphicon glyphicon-chevron-'+icons[visibility]+'"></span>&nbsp;'+btnLbl[visibility];
+            }
+
+            function btnLblAllText(visibility) {
+                return '<span class="glyphicon glyphicon-chevron-'+icons[visibility]+'"></span>&nbsp;'+btnLblAll[visibility];
+            }
+            
+            var toggleRows = function() {
+                var $this = $(this);
+                var toggleForm = this.id;
+                var visible = btnLbl.indexOf($this.text().trim()); // visible when button says "Collapse"
+                if (visible) {
+                    // collapse and switch button lbl to "Expand" when expanded
+                    $this.html(btnLblText(0)); 
+                    $('table.ReportTableWithBorder tr.'+toggleForm).hide();
+                } else {
+                    // expand and switch button lbl to "Collapse" when collapsed
+                    $this.html(btnLblText(1)); 
+                    $('table.ReportTableWithBorder tr.'+toggleForm).show();
+                }
+            };
+
+            var toggleAllRows = function() {
+                var $this = $(this);
+                var toggleType = btnLblAll.indexOf($this.text().trim());
+                // trigger click on all buttons with text corresponding to the visibility e.g. if Collapse all, all the Collapse buttons
+                $('table.ReportTableWithBorder button.toggle-rows:contains("'+btnLbl[toggleType]+'")').trigger('click');
+                $this.html(btnLblAllText((toggleType)?0:1));
+            };
+            
+            $('table.ReportTableWithBorder:first > tbody > tr').each(function() { // main table.ReportTableWithBorder trs only - ignore table.ReportTableWithBorder subtables for sql fields
+                var rowTDs = $(this).find('td');
+                if (rowTDs.length===0) {
+                    // this is the th row - do nothing
+                } else if (rowTDs.length===1) {
+                    // this is a form header row
+                    //  - extract the form ref from the final span (<span style="margin-left:10px;color:#444;">(instrument_name)</span>
+                    //  - add toggle button
+                    currentForm = $(rowTDs[0]).find('span').last().html().replace('(','').replace(')','');
+                    $('<button type="button" id="toggle-'+currentForm+'" class="btn btn-xs btn-primary toggle-rows" style="float:right;" data-toggle="button">'+btnLblText(defaultVisibility)+'</button>')
+                            .on('click', toggleRows)
+                            .appendTo(rowTDs[0]);
+                } else {
+                    // this is a variable's tr
+                    //  - add a class to target with the toggle
+                    //  - hide if default is hidden
+                    $(this).addClass("toggle-"+currentForm);
+                    if (!defaultVisibility) { $(this).hide(); }
+                }
+            });
+
+            $('<button type="button" id="toggle-all-forms" class="btn btn-xs btn-primary" style="float:right;margin:5px;" data-toggle="button">'+btnLblAllText(defaultVisibility)+'</button>')
+                    .on('click', toggleAllRows)
+                    .insertBefore('table.ReportTableWithBorder:first');
+        });
+    })(window, document, jQuery);
+</script>
+                        <?php
+                }
+        }
+        
+        protected function getDefaultVisibility() {
+                $defaultVisibility = $this->getProjectSetting('default-visibility');
+                if ($defaultVisibility!='0' && $defaultVisibility!='1') {
+                        $defaultVisibility = self::DEFAULT_VISIBILITY;
+                        $this->setProjectSetting('default-visibility', $defaultVisibility);
+                }
+                return $defaultVisibility;
+        }
+        
+        protected function getShowButtonText() {
+                return $this->getButtonText('button-text-show', self::DEFAULT_TEXT_SHOW);
+        }
+        
+        protected function getShowAllButtonText() {
+                return $this->getButtonText('button-text-show-all', self::DEFAULT_TEXT_SHOW_ALL);
+        }
+        
+        protected function getHideButtonText() {
+                return $this->getButtonText('button-text-hide', self::DEFAULT_TEXT_HIDE);
+        }
+        
+        protected function getHideAllButtonText() {
+                return $this->getButtonText('button-text-hide-all', self::DEFAULT_TEXT_HIDE_ALL);
+        }
+        
+        protected function getButtonText($setting, $default) {
+                $btnText = $this->getProjectSetting($setting);
+
+                if ($btnText=='') {
+                        $this->setProjectSetting($setting, $default);
+                        $btnText = $default;
+                }
+                return REDCap::escapeHtml($btnText);
+        }
+}
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..ae0a447
--- /dev/null
+++ b/README.md
@@ -0,0 +1,16 @@
+********************************************************************************
+# Codebook Concertina
+
+Luke Stevens, Murdoch Children's Research Institute https://www.mcri.edu.au
+
+********************************************************************************
+## Summary
+
+The Codebook page displays a table of all project variables in sections 
+corresponding to the instrument in which they appear. 
+
+This module provides a button in each instrument header that the user may click 
+to collapse or expand the fields for that instrument. A "Collapse all"/"Expand 
+all" button is also added above the table.
+
+********************************************************************************
\ No newline at end of file
diff --git a/config.json b/config.json
new file mode 100644
index 0000000..4019223
--- /dev/null
+++ b/config.json
@@ -0,0 +1,72 @@
+{
+	"name": "Codebook Concertina",
+
+	"description": "On the Codebook page, expand and collapse the table rows for the fields of each instrument.",
+
+	"namespace": "MCRI\\CodebookConcertina",
+
+	"authors": [
+		{
+			"name": "Luke Stevens",
+			"email": "luke.stevens@mcri.edu.au",
+			"institution": "Murdoch Children's Research Institute"
+		}
+	],
+
+	"permissions": [
+                "redcap_every_page_top"
+	],
+
+        "enable-every-page-hooks-on-system-pages": false,
+
+        "links": {
+        },
+        
+        "no-auth-pages": [
+        ],
+
+	"system-settings": [
+        ],
+
+	"project-settings": [
+                {
+			"key": "default-visibility",
+			"name": "Default visibility of codebook variable rows",
+			"required": true,
+			"type": "radio",
+                        "choices": [
+				{ "value": "0", "name": "Collapsed" },
+				{ "value": "1", "name": "Expanded" }
+                        ],
+			"default": "1"
+		},
+                {
+                         "key": "button-text-show",
+                         "name": "Button text 'Expand instrument'",
+                         "required": true,
+                         "type": "text",
+                         "default": "Expand"
+                },
+                {
+                         "key": "button-text-show-all",
+                         "name": "Button text 'Expand all'",
+                         "required": true,
+                         "type": "text",
+                         "default": "Expand all instruments"
+                },
+                {
+                         "key": "button-text-hide",
+                         "name": "Button text 'Collapse instrument'",
+                         "required": true,
+                         "type": "text",
+                         "default": "Collapse"
+                },
+                {
+                         "key": "button-text-hide-all",
+                         "name": "Button text 'Collapse all'",
+                         "required": true,
+                         "type": "text",
+                         "default": "Collapse all instruments"
+                }
+        ]
+}