diff --git a/.eslintrc b/.eslintrc
index 20c00deb09..edc9e07fdd 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -1,6 +1,26 @@
 {
-  "extends": ["react-app"],
+  "extends": [
+    "react-app",
+    "react-app/jest",
+    "eslint:recommended",
+    "plugin:@typescript-eslint/recommended",
+    "plugin:react/recommended",
+    "plugin:react-hooks/recommended"
+  ],
   "rules": {
-    "import/no-anonymous-default-export": "off"
-  }
+    "import/no-anonymous-default-export": "off",
+    "@typescript-eslint/ban-types": "off",
+    "@typescript-eslint/explicit-module-boundary-types": "off",
+    "no-prototype-builtins": "off",
+    "react/prop-types": "off",
+    "react/display-name": "off"
+  },
+  "ignorePatterns": [
+    "node_modules",
+    "build",
+    "coverage",
+    "src/test",
+    "*.js",
+    "*.spec.*"
+  ]
 }
diff --git a/src/app/components/AccessibilityButtonsWrapper.tsx b/src/app/components/AccessibilityButtonsWrapper.tsx
index 1058069aa2..d2f3288dea 100644
--- a/src/app/components/AccessibilityButtonsWrapper.tsx
+++ b/src/app/components/AccessibilityButtonsWrapper.tsx
@@ -26,7 +26,7 @@ const OpenKeyboardShortcutsMenuLink = () => {
   </FormattedMessage>;
 };
 
-export default class AccessibilityButtonsWrapper extends Component {
+export default class AccessibilityButtonsWrapper extends Component<React.PropsWithChildren<object>> {
   public mainContent: HTMLDivElement | undefined;
 
   public render() {
diff --git a/src/app/components/DotMenu.tsx b/src/app/components/DotMenu.tsx
index 828d5dbe42..817eaf322f 100644
--- a/src/app/components/DotMenu.tsx
+++ b/src/app/components/DotMenu.tsx
@@ -20,8 +20,8 @@ export const DotMenuIcon = styled(EllipsisV)`
 
 // tslint:disable-next-line:variable-name
 export const DotMenuToggle = styled(
-  React.forwardRef<HTMLDivElement, {isOpen: boolean}>(
-    ({isOpen, ...props}, ref) => {
+  React.forwardRef(
+    ({isOpen, ...props}: {isOpen: boolean}, ref) => {
 
       return (
         <PlainButton aria-label='Actions' aria-expanded={isOpen} {...props} ref={ref}>
diff --git a/src/app/components/ScrollOffset.tsx b/src/app/components/ScrollOffset.tsx
index 7bb670b55a..29b18b94de 100644
--- a/src/app/components/ScrollOffset.tsx
+++ b/src/app/components/ScrollOffset.tsx
@@ -107,7 +107,7 @@ export default class ScrollOffset extends React.Component<ScrollOffsetProps> {
     }
   };
 
-  private checkScroll = (maxChecks: number = 1) => {
+  private checkScroll = (maxChecks = 1) => {
     let scrolls = 0;
     const handler = () => {
       scrolls++;
diff --git a/src/app/content/components/Topbar/index.tsx b/src/app/content/components/Topbar/index.tsx
index 72c4f8605d..5109f57a17 100644
--- a/src/app/content/components/Topbar/index.tsx
+++ b/src/app/content/components/Topbar/index.tsx
@@ -38,7 +38,7 @@ interface Props {
   bookTheme: string;
   textSize: TextResizerValue | null;
   setTextSize: (size: TextResizerValue) => void;
-  selectedResult: any;
+  selectedResult: unknown;
 }
 
 type CommonSearchInputParams = Pick<
@@ -217,7 +217,9 @@ function AltSCycler({hasSearchResults}: {hasSearchResults: boolean}) {
       ].map((q) => document?.querySelector<HTMLElement>(q));
 
       // Determine which region we are in (if any)
-      const currentSectionIndex = targets.findIndex((el) => el?.contains(document?.activeElement!));
+      const currentSectionIndex = targets.findIndex((el) =>
+        document?.activeElement && el?.contains(document.activeElement)
+      );
 
       // If not in any, go to search input
       if (currentSectionIndex < 0) {
diff --git a/src/app/content/components/popUp/ChapterFilter.tsx b/src/app/content/components/popUp/ChapterFilter.tsx
index 9ca7ddb600..c4750f50a0 100644
--- a/src/app/content/components/popUp/ChapterFilter.tsx
+++ b/src/app/content/components/popUp/ChapterFilter.tsx
@@ -54,7 +54,7 @@ const ChapterTitle = styled.span`
   }
 `;
 
-const chunk = <T extends any>(sections: T[]) => {
+const chunk = <T extends unknown>(sections: T[]) => {
   const cutoff = Math.max(20, Math.ceil(sections.length / 2));
   return [sections.slice(0, cutoff), sections.slice(cutoff)].filter((arr) => arr.length > 0);
 };
diff --git a/src/app/content/highlights/components/SummaryPopup/HighlightListElement.tsx b/src/app/content/highlights/components/SummaryPopup/HighlightListElement.tsx
index 22f965c4c5..5b46c80825 100644
--- a/src/app/content/highlights/components/SummaryPopup/HighlightListElement.tsx
+++ b/src/app/content/highlights/components/SummaryPopup/HighlightListElement.tsx
@@ -175,7 +175,7 @@ const HighlightListElement = ({ highlight, locationFilterId, pageId }: Highlight
       }
     </HighlightContentWrapper>
     {isDeleting && <HighlightDeleteWrapper
-      deletingWhat={Boolean(highlight.annotation) ? 'both' : 'highlight'}
+      deletingWhat={highlight.annotation ? 'both' : 'highlight'}
       onCancel={() => setIsDeleting(false)}
       onDelete={confirmDelete}
     />}
diff --git a/src/app/content/launchToken.ts b/src/app/content/launchToken.ts
index cf6e4ea932..2462878b03 100644
--- a/src/app/content/launchToken.ts
+++ b/src/app/content/launchToken.ts
@@ -24,7 +24,9 @@ export const decodeToken = (launchToken: string | undefined) => {
     // and into their own claims of the token. during transition try to decode
     // sub and apply it to the token data so it works either way.
     Object.assign(token, JSON.parse(token.sub));
-  } catch (e) { } // tslint:disable-line
+  } catch (e) {
+    // let it go
+  }
 
   return token;
 };
diff --git a/src/app/content/practiceQuestions/reducer.ts b/src/app/content/practiceQuestions/reducer.ts
index cbb2f1b29d..268dc274ca 100644
--- a/src/app/content/practiceQuestions/reducer.ts
+++ b/src/app/content/practiceQuestions/reducer.ts
@@ -40,7 +40,7 @@ const reducer: Reducer<State, AnyAction> = (state = initialState, action): State
       return {...state, currentQuestionIndex: state.currentQuestionIndex === null ? 0 : state.currentQuestionIndex + 1};
     case getType(actions.setQuestions):
       return {...state, loading: false, questions: action.payload};
-    case getType(actions.setAnswer):
+    case getType(actions.setAnswer): {
       const { questionId, answer } = action.payload;
       return {
         ...state,
@@ -49,6 +49,7 @@ const reducer: Reducer<State, AnyAction> = (state = initialState, action): State
           [questionId]: answer,
         },
       };
+    }
     case getType(actions.finishQuestions):
       return {...state, currentQuestionIndex: null};
     default:
diff --git a/src/app/content/search/components/SearchResultsSidebar/SidebarSearchInput.tsx b/src/app/content/search/components/SearchResultsSidebar/SidebarSearchInput.tsx
index bc58265792..25b514c548 100644
--- a/src/app/content/search/components/SearchResultsSidebar/SidebarSearchInput.tsx
+++ b/src/app/content/search/components/SearchResultsSidebar/SidebarSearchInput.tsx
@@ -5,6 +5,7 @@ import theme from '../../../../theme';
 import { assertDocument } from '../../../../utils';
 import * as TopbarStyled from '../../../components/Topbar/styled';
 import { ResultsSidebarProps } from './SearchResultsBarWrapper';
+import { HTMLInputElement } from '@openstax/types/lib.dom';
 import * as Styled from './styled';
 
 interface State {
@@ -59,7 +60,7 @@ export class SidebarSearchInput extends Component<ResultsSidebarProps> {
   public newButtonEnabled = !!this.props.searchButtonColor;
 
   public onSearchChange = (e: React.FormEvent<HTMLInputElement>) => {
-    this.setState({ query: (e.currentTarget as any).value, formSubmitted: false });
+    this.setState({ query: (e.currentTarget as HTMLInputElement).value, formSubmitted: false });
   };
 
   public onSearchSubmit = (e: React.FormEvent) => {
diff --git a/src/app/content/search/components/SearchResultsSidebar/styled.tsx b/src/app/content/search/components/SearchResultsSidebar/styled.tsx
index aa718378c2..3109371dd5 100644
--- a/src/app/content/search/components/SearchResultsSidebar/styled.tsx
+++ b/src/app/content/search/components/SearchResultsSidebar/styled.tsx
@@ -276,7 +276,7 @@ interface SectionContentPreviewProps extends React.ComponentProps<typeof Content
 // tslint:disable-next-line:variable-name
 export const SectionContentPreview = styled(
   React.forwardRef<HTMLAnchorElement, SectionContentPreviewProps>(
-    ({selectedResult, ...props}, ref) => <ContentLinkComponent {...props} ref={ref} />
+    ({selectedResult, ...props}: {selectedResult: unknown}, ref) => <ContentLinkComponent {...props} ref={ref} />
   )
 )`
   ${labelStyle}
diff --git a/src/app/context/Services.tsx b/src/app/context/Services.tsx
index b19f127877..6eb128201c 100644
--- a/src/app/context/Services.tsx
+++ b/src/app/context/Services.tsx
@@ -28,7 +28,7 @@ interface ServiceConsumer {
 export default <P extends ServiceConsumer>(Component: React.ComponentType<P>) =>
   (props: Pick<P, Exclude<keyof P, keyof ServiceConsumer>>) => <Consumer>
     {(services) => {
-      // @ts-ignore - remove this when https://github.com/Microsoft/TypeScript/issues/28748 is resolved
+      // @ts-expect-error - remove this when https://github.com/Microsoft/TypeScript/issues/28748 is resolved
       return <Component services={services} {...props} />;
     }}
   </Consumer>;
diff --git a/src/app/developer/components/Panel.tsx b/src/app/developer/components/Panel.tsx
index 1794274c58..2473bae2ee 100644
--- a/src/app/developer/components/Panel.tsx
+++ b/src/app/developer/components/Panel.tsx
@@ -12,7 +12,7 @@ const Wrappper = styled.div`
 `;
 
 // tslint:disable-next-line:variable-name
-const Panel: React.SFC<Props> = ({title, children}) => <div>
+const Panel = ({title, children}: React.PropsWithChildren<Props>) => <div>
   <H2>{title}</H2>
   <Wrappper>
     {children}
diff --git a/src/app/domUtils.ts b/src/app/domUtils.ts
index de26be07aa..b2299c5fb8 100644
--- a/src/app/domUtils.ts
+++ b/src/app/domUtils.ts
@@ -7,8 +7,8 @@ import { AppServices, Store } from './types';
 import { assertDefined, assertDocument, assertWindow } from './utils';
 import debounce from 'lodash/debounce';
 
-export const SCROLL_UP: 'scroll_up' = 'scroll_up';
-export const SCROLL_DOWN: 'scroll_down' = 'scroll_down';
+export const SCROLL_UP = 'scroll_up';
+export const SCROLL_DOWN = 'scroll_down';
 
 export const getTouchDirection = (last: TouchEvent, next: TouchEvent) =>
   next.touches[0].clientY > last.touches[0].clientY
@@ -174,8 +174,8 @@ export const onPageFocusChange = (
 };
 
 const eventTypeMap = {
-  focusin: 'FocusEvent' as 'FocusEvent',
-  focusout: 'FocusEvent' as 'FocusEvent',
+  focusin: 'FocusEvent' as const,
+  focusout: 'FocusEvent' as const,
 };
 type EventTypeMap = typeof eventTypeMap;
 // this ['prototype'] is only necessary because of the duplicate names in lib.dom.d.ts, if we
diff --git a/src/app/featureFlags/reducer.ts b/src/app/featureFlags/reducer.ts
index 2b21e7eba8..c40e7d865a 100644
--- a/src/app/featureFlags/reducer.ts
+++ b/src/app/featureFlags/reducer.ts
@@ -7,10 +7,12 @@ import { State } from './types';
 
 export const initialState: State = {};
 
-const reducer: Reducer<State, AnyAction> = (state = initialState, action): any => {
+const reducer: Reducer<State, AnyAction> = (state = initialState, action) => {
+
     switch (action.type) {
-        case getType(receiveExperiments):
+        case getType(receiveExperiments): {
             const [id, variant] = action.payload;
+
             if (variant && experimentIds[id]) {
                 const experimentName = experimentIds[id];
                 const variantIndex = parseInt(variant, 10);
@@ -18,6 +20,7 @@ const reducer: Reducer<State, AnyAction> = (state = initialState, action): any =
                 return {...state, [experimentName]: variantName};
             }
             return state;
+        }
         case getType(receiveFeatureFlags):
             return action.payload.reduce((result, flag) => ({...result, [flag]: true}), {...state});
         default:
diff --git a/src/app/navigation/types.ts b/src/app/navigation/types.ts
index 2160a7a483..31912d9f41 100644
--- a/src/app/navigation/types.ts
+++ b/src/app/navigation/types.ts
@@ -42,7 +42,7 @@ export interface RouteStateType {
 
 export interface Route<
   P extends RouteParamsType = {},
-  // @ts-ignore: 'S' is declared but its value is never read.
+  // @ts-expect-error: 'S' is declared but its value is never read.
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   S extends RouteStateType = {}
 > {
diff --git a/src/app/notifications/acceptCookies.ts b/src/app/notifications/acceptCookies.ts
index e4f0dd3b13..17a0421f63 100644
--- a/src/app/notifications/acceptCookies.ts
+++ b/src/app/notifications/acceptCookies.ts
@@ -1,6 +1,6 @@
 import * as Cookies from 'js-cookie';
 
-const acknowledgedKey: string = 'cookie_notice_acknowledged';
+const acknowledgedKey = 'cookie_notice_acknowledged';
 
 export const doAcceptCookies = () => {
   Cookies.set(acknowledgedKey, 'true', {expires: 365 * 20});
diff --git a/src/app/notifications/dismissAppMessages.ts b/src/app/notifications/dismissAppMessages.ts
index 57150b76c9..f50be01f54 100644
--- a/src/app/notifications/dismissAppMessages.ts
+++ b/src/app/notifications/dismissAppMessages.ts
@@ -2,7 +2,7 @@ import { differenceInDays } from 'date-fns';
 import * as Cookies from 'js-cookie';
 import { Message } from './types';
 
-const messageDismissedPrefix: string = 'message_dismissed';
+const messageDismissedPrefix = 'message_dismissed';
 const getMessageKey = (message: Message) => `${messageDismissedPrefix}_${message.id}`;
 
 export const dismissAppMessage = (message: Message) => {
diff --git a/src/app/notifications/reducer.ts b/src/app/notifications/reducer.ts
index 95c2fa3cfa..0fea066173 100644
--- a/src/app/notifications/reducer.ts
+++ b/src/app/notifications/reducer.ts
@@ -14,7 +14,7 @@ export const initialState: State = {
   toastNotifications: [],
 };
 
-export const appMessageType =  'Notification/appMessage' as 'Notification/appMessage';
+export const appMessageType =  'Notification/appMessage' as const;
 
 const isNewMessage = (state: State, message: Message) =>
   !state.modalNotifications.find((existingMessage) => {
diff --git a/src/app/utils/browser-assertions.ts b/src/app/utils/browser-assertions.ts
index 21fe097f77..2b74c9faf3 100644
--- a/src/app/utils/browser-assertions.ts
+++ b/src/app/utils/browser-assertions.ts
@@ -1,4 +1,4 @@
-export const assertWindow = (message: string = 'BUG: Window is undefined') => {
+export const assertWindow = (message = 'BUG: Window is undefined') => {
   if (typeof(window) === 'undefined') {
     throw new Error(message);
   }
@@ -6,7 +6,7 @@ export const assertWindow = (message: string = 'BUG: Window is undefined') => {
   return window;
 };
 
-export const assertDocument = (message: string = 'BUG: Document is undefined') => {
+export const assertDocument = (message = 'BUG: Document is undefined') => {
   if (typeof(document) === 'undefined') {
     throw new Error(message);
   }
@@ -14,7 +14,7 @@ export const assertDocument = (message: string = 'BUG: Document is undefined') =
   return document;
 };
 
-export const assertDocumentElement = (message: string = 'BUG: Document Element is null') => {
+export const assertDocumentElement = (message = 'BUG: Document Element is null') => {
   const documentElement = assertDocument().documentElement;
 
   if (documentElement === null) {
diff --git a/src/canonicalBookMap/americanGovernment.ts b/src/canonicalBookMap/americanGovernment.ts
index ca4281ac32..3c1196f5cb 100644
--- a/src/canonicalBookMap/americanGovernment.ts
+++ b/src/canonicalBookMap/americanGovernment.ts
@@ -50,7 +50,7 @@ export default {
       'ed22cb13-2f14-460f-a603-fb1631f4c6f6': '7760a2b3-c3b9-416c-9520-b8cc4fa954fa',
       /* 4.4 Interpreting the Bill of Rights to the same module in 2e */
       'fdf44e79-776e-477e-963c-a6c0a98c434a': 'cb752abe-3cf9-4da4-8fc5-60b9e3752e5a',
-      /* 5.0 Introduction to the same module in 2e */
+      /* 5.0 Introduction to the same module in 2e */
       '9fab3e71-ddb5-4dd9-bfd4-c9bc9b98141e': '9d5dd1d4-a37c-45be-a6c5-1af41cabed33',
       /* 5.1 What Are Civil Rights and How Do We Identify Them? to the same module in 2e */
       '75bad956-ba62-4639-92cf-d25fc3bdd9f1': '2d27051a-78f8-4af2-acc1-d6ca2217ef70',
diff --git a/src/gateways/googleAnalyticsClient.spec.ts b/src/gateways/googleAnalyticsClient.spec.ts
index cd351683dd..e2a6fa2dcb 100644
--- a/src/gateways/googleAnalyticsClient.spec.ts
+++ b/src/gateways/googleAnalyticsClient.spec.ts
@@ -215,7 +215,7 @@ describe('GoogleAnalyticsClient', () => {
         client.setTagIds(['foo']);
         mockGtag.mockClear();
         client.trackPageView('/some/path', { utm_source: 'source' });
-        expect(mockGtag).toHaveBeenCalledWith('set', {
+        expect(mockGtag).toHaveBeenCalledWith('set', undefined, {
           campaignMedium: 'unset',
           campaignSource: 'source',
         });
diff --git a/src/gateways/googleAnalyticsClient.ts b/src/gateways/googleAnalyticsClient.ts
index 87c207763a..04c2b3ab98 100644
--- a/src/gateways/googleAnalyticsClient.ts
+++ b/src/gateways/googleAnalyticsClient.ts
@@ -207,9 +207,9 @@ class GoogleAnalyticsClient {
     this.pendingCommands = [];
   }
 
-  private executeCommand(command: Command, queueTime: number = 0) {
+  private executeCommand(command: Command, queueTime = 0) {
     if (command.name === 'set') {
-      this.gtag('set', command.payload);
+      this.gtag('set', undefined, command.payload);
       return;
     }
 
@@ -231,7 +231,7 @@ class GoogleAnalyticsClient {
   }
 
   // The real, low-level Google Analytics gtag function
-  private gtag(commandName: string, ...params: any[]) {
+  private gtag(commandName: string, ...params: [string?, object?]) {
     return assertWindow().gtag(commandName, ...params);
   }
 
diff --git a/src/typings/WeakMap.d.ts b/src/typings/WeakMap.d.ts
index abe9b6a9b4..353d158005 100644
--- a/src/typings/WeakMap.d.ts
+++ b/src/typings/WeakMap.d.ts
@@ -35,10 +35,6 @@ declare module 'weak-map' {
     clear(): void;
   }
 
-  interface WeakMapConstructor {
-    new(): WeakMap;
-  }
-
   class WeakMap {
     constructor();
   }
diff --git a/src/typings/global.d.ts b/src/typings/global.d.ts
index c337a49dee..1648c77721 100644
--- a/src/typings/global.d.ts
+++ b/src/typings/global.d.ts
@@ -56,7 +56,7 @@ declare global {
       prototype: Event;
       new<T>(typeArg: string, eventInitDict?: EventInit<T>): Event<T>;
     };
-    MathJax: any;
+    MathJax: any; // eslint-disable-line @typescript-eslint/no-explicit-any
     ga: UniversalAnalytics.ga;
     dataLayer: object[];
     oxDLF: object[];
@@ -64,6 +64,7 @@ declare global {
     gtag: (eventKey?: string, eventVal?: string, eventObj?: object) => boolean | void;
   }
 
+  /* eslint-disable no-var */
   var fetch: (input: dom.RequestInfo, init?: dom.RequestInit) => Promise<Response>;
   var window: Window | undefined;
   var document: dom.Document | undefined;
diff --git a/src/typings/rangy.d.ts b/src/typings/rangy.d.ts
index 1c2131d2d2..1ea628dfcb 100644
--- a/src/typings/rangy.d.ts
+++ b/src/typings/rangy.d.ts
@@ -57,6 +57,6 @@ declare module 'rangy' {
   }
 
   export default rangy;
-  declare var rangy: RangyStatic;
+  declare const rangy: RangyStatic;
   type NativeRange = import ('@openstax/types/lib.dom').Range;
 }