diff --git a/extension/background.ts b/extension/background.ts
index 89d625e..1eadb24 100644
--- a/extension/background.ts
+++ b/extension/background.ts
@@ -1,9 +1,9 @@
-var browser = browser || chrome;
+var browser : Browser = browser || chrome;
 
-var PENDING_SUBMISSIONS = ':PENDING_SUBMISSIONS'
-var MIGRATION = ':MIGRATION'
+const PENDING_SUBMISSIONS = ':PENDING_SUBMISSIONS'
+const MIGRATION = ':MIGRATION'
 
-var CURRENT_VERSION = 100018;
+const CURRENT_VERSION = 100018;
 
 // If a user labels one of these URLs, they're making a mistake. Ignore the label.
 // This list includes:
@@ -232,7 +232,7 @@ var badIdentifiersArray = [
     'youtube.com/redirect',
     'youtube.com/watch',
 ];
-var badIdentifiers = {};
+var badIdentifiers : {[id: string]: true} = {};
 badIdentifiersArray.forEach(x => badIdentifiers[x] = true);
 
 var lastSubmissionError = null;
@@ -287,9 +287,9 @@ browser.storage.local.get(['overrides', 'accepted', 'installationId'], v => {
     }
 })
 
-var bloomFilters = [];
+const bloomFilters : BloomFilter[] = [];
 
-function loadBloomFilter(name) {
+function loadBloomFilter(name: string) {
 
     var url = browser.extension.getURL('data/' + name + '.dat');
     fetch(url).then(response => {
@@ -341,7 +341,7 @@ loadBloomFilter('t-friendly');
 
 
 
-function createContextMenu(text, id) {
+function createContextMenu(text: string, id: ContextMenuCommand) {
     browser.contextMenus.create({
         id: id,
         title: text,
diff --git a/extension/content.ts b/extension/content.ts
index fa9cbde..fd87914 100644
--- a/extension/content.ts
+++ b/extension/content.ts
@@ -1,4 +1,4 @@
-var browser = browser || chrome;
+var browser : Browser = browser || chrome;
 
 var hostname = typeof (location) != 'undefined' ? location.hostname : '';
 if (hostname.startsWith('www.')) {
@@ -15,7 +15,7 @@ function fixupSiteStyles() {
     if (hostname == 'reddit.com') {
         myself = document.querySelector('#header-bottom-right .user a');
         if (!myself) {
-            var m = document.querySelector('#USER_DROPDOWN_ID');
+            var m : any = document.querySelector('#USER_DROPDOWN_ID');
             if (m) {
                 m = [...m.querySelectorAll('*')].filter(x => x.childNodes.length == 1 && x.firstChild.nodeType == 3).map(x => x.textContent)[0]
                 if (m) myself = 'reddit.com/user/' + m;
@@ -23,7 +23,7 @@ function fixupSiteStyles() {
         }
     }
     if (hostname == 'facebook.com') {
-        var m = document.querySelector("[id^='profile_pic_header_']")
+        var m : any = document.querySelector("[id^='profile_pic_header_']")
         if (m) myself = 'facebook.com/' + captureRegex(m.id, /header_(\d+)/);
     }
     if (hostname == 'medium.com') {
diff --git a/extension/definitions.d.ts b/extension/definitions.d.ts
new file mode 100644
index 0000000..4ef7c93
--- /dev/null
+++ b/extension/definitions.d.ts
@@ -0,0 +1,6 @@
+declare class BloomFilter {
+    constructor(data: Uint32Array, k: number);
+    test(key: string): boolean;
+    name: string;
+}
+type ContextMenuCommand = 'mark-t-friendly' | 'mark-transphobic' | 'mark-none' | 'help';
diff --git a/extension/help.ts b/extension/help.ts
index f0dc3ff..7c9dad2 100644
--- a/extension/help.ts
+++ b/extension/help.ts
@@ -1,4 +1,4 @@
-var browser = browser || chrome;
+var browser : Browser = browser || chrome;
 
 document.getElementById('cancelButton').addEventListener('click', () => {
 
diff --git a/extension/webextensions.d.ts b/extension/webextensions.d.ts
new file mode 100644
index 0000000..e972bb8
--- /dev/null
+++ b/extension/webextensions.d.ts
@@ -0,0 +1,18 @@
+declare type Browser = {
+
+    runtime: {
+
+    }
+    
+    storage: {
+        local: BrowserStorage
+    }
+    extension: {
+        
+    }
+}
+declare type BrowserStorage = {
+
+}
+declare var browser : Browser;
+declare var chrome : Browser;
\ No newline at end of file