diff --git a/api/src/index.ts b/api/src/index.ts
index b466c42..45acba6 100644
--- a/api/src/index.ts
+++ b/api/src/index.ts
@@ -4,7 +4,7 @@ import { existsSync } from 'fs';
 // eslint-disable-next-line import/no-duplicates
 import * as express from 'express';
 // eslint-disable-next-line import/no-duplicates
-import { Request, Response, NextFunction } from 'express';
+import { type Request, type Response, type NextFunction } from 'express';
 
 import * as bodyParser from 'body-parser';
 import * as morgan from 'morgan';
@@ -64,9 +64,9 @@ app.get('/sitemap.xml', async (req, res) => {
 // frontend
 if (existsSync(join(__dirname, '../frontend'))) {
     // eslint-disable-next-line @typescript-eslint/no-var-requires
-    const assetsManifest: { [originalFilePath: string]: string } = require(join(__dirname, '../frontend', 'assets-manifest.json'));
+    const assetsManifest: Record<string, string> = require(join(__dirname, '../frontend', 'assets-manifest.json'));
 
-    const cacheHeaders: { [path: string]: string|undefined } = {};
+    const cacheHeaders: Record<string, string | undefined> = {};
 
     for (const originalFilePath in assetsManifest) {
         if (Object.prototype.hasOwnProperty.call(assetsManifest, originalFilePath)) {
diff --git a/api/src/models/container.model.ts b/api/src/models/container.model.ts
index 1a282a6..202b6ab 100644
--- a/api/src/models/container.model.ts
+++ b/api/src/models/container.model.ts
@@ -40,17 +40,17 @@ export default class Container extends Model<Container> {
     @Default(null)
     @AllowNull
     @Column(DataType.TEXT)
-    public headerColor: string|null;
+    public headerColor: string | null;
 
     @Default(null)
     @AllowNull
     @Column(DataType.TEXT)
-    public headerImage: string|null;
+    public headerImage: string | null;
 
     @Default(null)
     @AllowNull
     @Column(DataType.TEXT)
-    public pinnedImage: string|null;
+    public pinnedImage: string | null;
 
     @Default(0)
     @Column(DataType.INTEGER)
@@ -67,13 +67,13 @@ export default class Container extends Model<Container> {
     @AfterUpdate
     @AfterCreate
     @AfterDestroy
-    static updatePageUpdatedAt(instance: Container): Promise<void> {
-        return (Page.findByPk(instance.pageSlug) as Promise<Page|null>).then((page): Promise<void> => {
-            if (page === null) return Promise.resolve();
+    static async updatePageUpdatedAt (instance: Container): Promise<void> {
+        await (Page.findByPk(instance.pageSlug)).then(async (page): Promise<void> => {
+            if (page === null) { await Promise.resolve(); return; }
 
             page.changed('updatedAt', true);
 
-            return page.save();
+            return await page.save();
         });
     }
 }
diff --git a/api/src/utils/EventsService.ts b/api/src/utils/EventsService.ts
index 1f5462b..f246c30 100644
--- a/api/src/utils/EventsService.ts
+++ b/api/src/utils/EventsService.ts
@@ -2,10 +2,10 @@ import * as equals from 'fast-deep-equal';
 import fetch from 'node-fetch';
 
 export interface ArmaEvent {
-    date: Date;
-    title: string;
-    url: string;
-    attendance: [number, number];
+    date: Date
+    title: string
+    url: string
+    attendance: [number, number]
 }
 
 export class ArmaEventsService {
@@ -13,21 +13,21 @@ export class ArmaEventsService {
     private static readonly FORUM_URI = 'https://forum.gruppe-adler.de';
     private static readonly TOPIC_TITLE_REGEX = /^\d{4}-\d{2}-\d{2}\s*,(\s*\w+\s*,)?\s*/i;
 
-    private static instance: ArmaEventsService|null = null;
+    private static instance: ArmaEventsService | null = null;
 
     private cachedEvents: ArmaEvent[] = [];
     private lastModified: Date = new Date(0);
 
     // this constructor is actually important to make sure it is private (singleton pattern)
     // eslint-disable-next-line no-useless-constructor, @typescript-eslint/no-empty-function
-    private constructor() {
+    private constructor () {
         this.cacheEvents();
 
         // fetch new events every half an hour
         setInterval(this.cacheEvents.bind(this), 1000 * 60 * 30);
     }
 
-    public static getInstance(): ArmaEventsService {
+    public static getInstance (): ArmaEventsService {
         if (this.instance === null) {
             this.instance = new ArmaEventsService();
         }
@@ -35,11 +35,11 @@ export class ArmaEventsService {
         return this.instance;
     }
 
-    public async getEvents(): Promise<{ events: ArmaEvent[], lastModified: Date }> {
+    public async getEvents (): Promise<{ events: ArmaEvent[], lastModified: Date }> {
         return { events: this.cachedEvents, lastModified: this.lastModified };
     }
 
-    public async cacheEvents(): Promise<void> {
+    public async cacheEvents (): Promise<void> {
         const events = await this.fetchEvents();
 
         if (!equals(this.cachedEvents, events)) {
@@ -48,12 +48,12 @@ export class ArmaEventsService {
         }
     }
 
-    private async fetchEvents(): Promise<ArmaEvent[]> {
+    private async fetchEvents (): Promise<ArmaEvent[]> {
         const response = await fetch(`${ArmaEventsService.FORUM_URI}/api/events/cid-3`);
         if (!response.ok) {
             throw new Error(`Error while trying to fetch events. Forum API responded with status code ${response.status}.`);
         }
-        const { topics } = await response.json() as { topics: Array<{ slug: string; titleRaw: string; tid: number; deleted: 1|0; timestamp: number }> };
+        const { topics } = await response.json() as { topics: Array<{ slug: string, titleRaw: string, tid: number, deleted: 1 | 0, timestamp: number }> };
 
         const rawEvents: Array<Omit<ArmaEvent, 'attendance'> & { tid: number }> = [];
         for (const topic of topics) {
@@ -83,9 +83,9 @@ export class ArmaEventsService {
         const firstFutureEvent = sortedEvents.findIndex(e => ArmaEventsService.isInFuture(e.date)) + 1;
         const filteredEvents = sortedEvents.slice(0, firstFutureEvent > 0 ? firstFutureEvent : sortedEvents.length).reverse().slice(0, 10);
 
-        const promises = filteredEvents.map(({ tid, ...rest }) => ArmaEventsService.fetchAttendance(tid).then((attendance): ArmaEvent => ({ ...rest, attendance })));
+        const promises = filteredEvents.map(async ({ tid, ...rest }) => await ArmaEventsService.fetchAttendance(tid).then((attendance): ArmaEvent => ({ ...rest, attendance })));
 
-        return Promise.all(promises);
+        return await Promise.all(promises);
     }
 
     /**
@@ -118,7 +118,7 @@ export class ArmaEventsService {
         if (!response.ok) {
             throw new Error(`Error while trying to fetch attendance for topic ${tid}. Forum API responded with status code ${response.status}.`);
         }
-        const { attendants } = await response.json() as { attendants: Array<{ probability: 0|0.5|1 }> };
+        const { attendants } = await response.json() as { attendants: Array<{ probability: 0 | 0.5 | 1 }> };
 
         let firm = 0;
         let maybe = 0;
diff --git a/api/src/utils/ResponseError.ts b/api/src/utils/ResponseError.ts
index 3e229e4..2a03813 100644
--- a/api/src/utils/ResponseError.ts
+++ b/api/src/utils/ResponseError.ts
@@ -3,7 +3,7 @@ export default class ReponseError extends Error {
 
     public status: number;
 
-    constructor(status: number, msg?: string) {
+    constructor (status: number, msg?: string) {
         super(msg);
         this.status = status;
     }
diff --git a/api/src/utils/UploadService.ts b/api/src/utils/UploadService.ts
index 7c5fa49..ba91d25 100644
--- a/api/src/utils/UploadService.ts
+++ b/api/src/utils/UploadService.ts
@@ -1,7 +1,7 @@
 import { existsSync, mkdirSync, writeFileSync, unlinkSync } from 'fs';
 
 export class UploadService {
-    private static instance: UploadService|null = null;
+    private static instance: UploadService | null = null;
     public static readonly UPLOADS_BASE_PATH = 'data/uploads';
 
     private static readonly MINE_TYPES = new Map<string, string>([
@@ -13,18 +13,18 @@ export class UploadService {
         ['image/bmp', 'bmp']
     ]);
 
-    public static get ALLOWED_MIME_TYPES(): string[] {
+    public static get ALLOWED_MIME_TYPES (): string[] {
         return Array.from(this.MINE_TYPES.keys());
     }
 
-    private constructor() {
+    private constructor () {
         // create directory if it doesn't exist already
         if (!existsSync(UploadService.UPLOADS_BASE_PATH)) {
             mkdirSync(UploadService.UPLOADS_BASE_PATH);
         }
     }
 
-    public static getInstance(): UploadService {
+    public static getInstance (): UploadService {
         if (this.instance === null) {
             this.instance = new UploadService();
         }
@@ -32,7 +32,7 @@ export class UploadService {
         return this.instance;
     }
 
-    public saveFile(buffer: Buffer, mimeType: string): string {
+    public saveFile (buffer: Buffer, mimeType: string): string {
         if (!UploadService.MINE_TYPES.has(mimeType.toLowerCase())) throw new Error(`MIME type '${mimeType}' is not allowed`);
 
         const fileEnding: string = UploadService.MINE_TYPES.get(mimeType.toLowerCase());
@@ -46,13 +46,13 @@ export class UploadService {
         return `${name}.${fileEnding}`;
     }
 
-    public removeFile(name: string): void {
+    public removeFile (name: string): void {
         if (!existsSync(`${UploadService.UPLOADS_BASE_PATH}/${name}`)) return;
 
         unlinkSync(`${UploadService.UPLOADS_BASE_PATH}/${name}`);
     }
 
-    private static randomName(): string {
+    private static randomName (): string {
         return (Math.random().toString(36).substr(2)) + (Math.random().toString(36).substr(2));
     }
 }
diff --git a/api/src/utils/express.ts b/api/src/utils/express.ts
index fb91f89..72b2c1a 100644
--- a/api/src/utils/express.ts
+++ b/api/src/utils/express.ts
@@ -1,4 +1,4 @@
-import { Request, Response, NextFunction, RequestHandler } from 'express';
+import { type Request, type Response, type NextFunction, type RequestHandler } from 'express';
 import { validationResult } from 'express-validator';
 import ResponseError from './ResponseError';
 
@@ -15,7 +15,7 @@ export const globalErrorHandler = (err: unknown, req: Request, res: Response, ne
     }
 
     let status = 500;
-    let msg: undefined|string;
+    let msg: undefined | string;
 
     if (err instanceof ResponseError) {
         status = err.status;
@@ -33,7 +33,7 @@ export const globalErrorHandler = (err: unknown, req: Request, res: Response, ne
     }
 };
 
-export function return422(req: Request, res: Response, next: NextFunction): void {
+export function return422 (req: Request, res: Response, next: NextFunction): void {
     const errors = validationResult(req);
     if (!errors.isEmpty()) {
         res.status(422).json({ errors: errors.array() });
diff --git a/api/src/utils/sitemap.ts b/api/src/utils/sitemap.ts
index 1d638f2..c12f37a 100644
--- a/api/src/utils/sitemap.ts
+++ b/api/src/utils/sitemap.ts
@@ -3,7 +3,7 @@ import { SitemapStream, streamToPromise } from 'sitemap';
 import { createGzip } from 'zlib';
 import { Page } from '../models';
 
-let cachedSitemap: Buffer|null = null;
+let cachedSitemap: Buffer | null = null;
 
 const BUILD_TIME_PATH = '/build-date.txt';
 let buildTime = new Date(0);
@@ -22,11 +22,11 @@ Page.addHook('afterCreate', cacheSitemap);
 Page.addHook('afterDestroy', cacheSitemap);
 Page.addHook('afterUpdate', cacheSitemap);
 
-async function cacheSitemap(): Promise<void> {
+async function cacheSitemap (): Promise<void> {
     cachedSitemap = await generateSitemap();
 }
 
-async function generateSitemap(): Promise<Buffer> {
+async function generateSitemap (): Promise<Buffer> {
     const smStream = new SitemapStream({ hostname: 'https://gruppe-adler.de/' });
     const pipeline = smStream.pipe(createGzip());
 
@@ -43,10 +43,10 @@ async function generateSitemap(): Promise<Buffer> {
 
     const prom = streamToPromise(pipeline);
     smStream.end();
-    return prom;
+    return await prom;
 }
 
-export async function getSitemap(): Promise<Buffer> {
+export async function getSitemap (): Promise<Buffer> {
     await initialCachePromise;
     return cachedSitemap;
 }
diff --git a/api/src/utils/sso.ts b/api/src/utils/sso.ts
index d54f85c..8d4d279 100644
--- a/api/src/utils/sso.ts
+++ b/api/src/utils/sso.ts
@@ -1,4 +1,4 @@
-import { Request, Response, NextFunction } from 'express/index';
+import { type Request, type Response, type NextFunction } from 'express/index';
 
 import fetch from 'node-fetch';
 import { globalErrorHandler } from './express';
@@ -8,11 +8,11 @@ import ReponseError from './ResponseError';
 const config = require('../../config/config.json');
 
 interface SSOUser {
-    admin: boolean;
-    groups: { tag: string; }[];
+    admin: boolean
+    groups: Array<{ tag: string }>
 }
 
-async function fetchUser(token: string): Promise<SSOUser|null> {
+async function fetchUser (token: string): Promise<SSOUser | null> {
     const res = await fetch(`${config.sso.domain}/api/v1/graphql`, {
         method: 'POST',
         headers: {
@@ -37,7 +37,7 @@ async function fetchUser(token: string): Promise<SSOUser|null> {
 
     if (!res.ok) throw new ReponseError(401);
 
-    const json = await res.json() as { data: { authenticate: SSOUser|null } };
+    const json = await res.json() as { data: { authenticate: SSOUser | null } };
 
     return json.data.authenticate;
 }
@@ -58,7 +58,7 @@ async function validateToken (token: string) {
     if (!admin && !isInGroup) throw new ReponseError(403);
 }
 
-function extractToken(req: Request): string {
+function extractToken (req: Request): string {
     if (req.cookies[config.sso.cookiename]) {
         return req.cookies[config.sso.cookiename];
     }
@@ -73,7 +73,7 @@ function extractToken(req: Request): string {
     throw new Error('Couldn\'t find token to extract');
 }
 
-export async function ssoCheckAuthorized(req: Request, res: Response, next: NextFunction): Promise<void> {
+export async function ssoCheckAuthorized (req: Request, res: Response, next: NextFunction): Promise<void> {
     let token: string;
     try {
         token = extractToken(req);
diff --git a/api/src/v1/routes/container.router.ts b/api/src/v1/routes/container.router.ts
index f936a49..7b9dc5b 100644
--- a/api/src/v1/routes/container.router.ts
+++ b/api/src/v1/routes/container.router.ts
@@ -15,7 +15,7 @@ const defaultContainerRules = [
     body('index').optional().isInt().toInt()
 ];
 
-type OptionalContainerFields = Partial<Pick<Container, 'heading'|'footer'|'content'|'headerColor'|'headerImage'|'pinnedImage'|'index'>>;
+type OptionalContainerFields = Partial<Pick<Container, 'heading' | 'footer' | 'content' | 'headerColor' | 'headerImage' | 'pinnedImage' | 'index'>>;
 
 const containerRouter = Router();
 
@@ -41,7 +41,7 @@ containerRouter.put('/:id', [
 ], wrapAsync(async (req, res) => {
     const { id, ...updateData } = matchedData(req) as OptionalContainerFields & Partial<Pick<Container, 'pageSlug'>> & Pick<Container, 'id'>;
 
-    const container: Container|null = await Container.findByPk(id);
+    const container: Container | null = await Container.findByPk(id);
 
     if (container === null) {
         throw new ReponseError(404, `Container with id '${id}' not found.`);
@@ -59,7 +59,7 @@ containerRouter.delete('/:id', [
 ], wrapAsync(async (req, res) => {
     const { id } = matchedData(req) as { id: number };
 
-    const container: Container|null = await Container.findByPk(id);
+    const container: Container | null = await Container.findByPk(id);
 
     if (container === null) {
         throw new ReponseError(404, `Container with id '${id}' not found.`);
diff --git a/api/src/v1/routes/page.router.ts b/api/src/v1/routes/page.router.ts
index c82694a..0726e77 100644
--- a/api/src/v1/routes/page.router.ts
+++ b/api/src/v1/routes/page.router.ts
@@ -10,7 +10,7 @@ const pageRouter = Router();
 pageRouter.get('/*', wrapAsync(async (req, res) => {
     const slug = req.path;
 
-    const page = await Page.findByPk(slug) as Page|null;
+    const page = await Page.findByPk(slug);
 
     if (page === null) {
         throw new ReponseError(404, `Page with slug '${slug}' not found.`);
@@ -31,9 +31,9 @@ pageRouter.put('/*', [
 ], wrapAsync(async (req, res) => {
     const slug = req.path;
 
-    const updateData = matchedData(req) as Partial<Pick<Page, 'toc'|'description'|'title'|'priority'>>;
+    const updateData = matchedData(req) as Partial<Pick<Page, 'toc' | 'description' | 'title' | 'priority'>>;
 
-    const page: Page|null = await Page.findByPk(slug);
+    const page: Page | null = await Page.findByPk(slug);
 
     if (page === null) {
         throw new ReponseError(404, `Page with slug '${slug}' not found.`);
@@ -53,7 +53,7 @@ pageRouter.post('/', [
     body('priority').optional().isFloat({ min: 0, max: 1 }).toFloat(),
     return422
 ], wrapAsync(async (req, res) => {
-    const data = matchedData(req) as Partial<Pick<Page, 'toc'|'description'|'title'|'priority'>> & Pick<Page, 'slug'>;
+    const data = matchedData(req) as Partial<Pick<Page, 'toc' | 'description' | 'title' | 'priority'>> & Pick<Page, 'slug'>;
 
     const page = await Page.create(data);
 
@@ -65,7 +65,7 @@ pageRouter.delete('/*', [
 ], wrapAsync(async (req, res) => {
     const slug = req.path;
 
-    const page: Page|null = await Page.findByPk(slug);
+    const page: Page | null = await Page.findByPk(slug);
 
     if (page === null) {
         throw new ReponseError(404, `Container with slug '${slug}' not found.`);
diff --git a/api/tsconfig.json b/api/tsconfig.json
index 9976c17..aa9cb57 100644
--- a/api/tsconfig.json
+++ b/api/tsconfig.json
@@ -7,6 +7,7 @@
         "target": "es6",
         "sourceMap": true,
         "outDir": "./build",
+        "strictNullChecks": true
     },
     "exclude": [
         "node_modules"