diff --git a/.gitignore b/.gitignore
index 9f11b75..5c6b34c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 .idea/
+www/res/scripts/*
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..fb21cbd
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,12 @@
+.DEFAULT_GOAL := build
+
+OUT=www/res/scripts
+
+${OUT}/locutus.js ${OUT}/usimp.js: src/locutus.ts src/usimp.ts
+	tsc
+
+build: ${OUT}/locutus.js ${OUT}/usimp.js
+	perl -i -pE 's/(\?v=[0-9]+\.[0-9]+\.[0-9]+\+)([0-9]+)/($$1).($$2+1)/eg' www/index.html
+
+clean:
+	rm -rf "${OUT}"
diff --git a/www/res/js/modules/locutus.js b/src/locutus.ts
similarity index 67%
rename from www/res/js/modules/locutus.js
rename to src/locutus.ts
index bf7e893..9d33442 100644
--- a/www/res/js/modules/locutus.js
+++ b/src/locutus.ts
@@ -1,26 +1,26 @@
 "use strict";
 
-import * as USIMP from "./usimp.js";
+import * as USIMP from "./usimp";
 
 export class App {
-    account;
-    defaultLocation;
-    main;
-    windows;
-    session;
+    account: USIMP.Account | null;
+    defaultLocation: string;
+    main: HTMLElement;
+    windows: HTMLElement;
+    session: USIMP.Session | null;
 
     constructor() {
-        if (localStorage.session === undefined) {
-            this.defaultLocation = '/welcome';
-            this.account = null;
-        } else {
-            const session = JSON.parse(localStorage.session);
-            this.defaultLocation = '/';
-            this.account = session.account;
-        }
+        this.defaultLocation = '/welcome';
+        this.account = null;
+        this.session = null;
 
-        this.main = document.getElementsByTagName("main")[0];
-        this.windows = document.getElementById("windows");
+        const main = document.getElementsByTagName("main")[0];
+        if (!main) throw Error("Element <main> not found");
+        this.main = main;
+
+        const windows = document.getElementById("windows");
+        if (!windows) throw Error("Element #windows not found");
+        this.windows = windows;
 
         window.addEventListener("hashchange", event => {
             this.handleUrl(event.newURL);
@@ -29,21 +29,21 @@ export class App {
         this.handleUrl(document.URL);
     }
 
-    setHash(hash) {
+    setHash(hash: string) {
         const url = new URL(document.URL);
         url.hash = hash;
         location.href = url.toString();
     }
 
-    handleUrl(url) {
+    handleUrl(url: string) {
         this.handleHash(new URL(url).hash);
     }
 
-    handleHash(hash) {
+    handleHash(hash: string) {
         if (hash[0] === '#') hash = hash.substr(1);
 
         const defaultCase = () => {
-            history.replaceState(null, null, `#${this.defaultLocation}`);
+            history.replaceState(null, document.title, `#${this.defaultLocation}`);
             this.handleHash(this.defaultLocation);
         }
 
@@ -78,7 +78,7 @@ export class App {
         }
     }
 
-    async login(accountName, domainName, password) {
+    async login(accountName: string, domainName: string, password: string) {
         let domain;
         try {
             domain = await USIMP.Domain.fromName(domainName);
@@ -135,13 +135,15 @@ export class App {
         this.windows.appendChild(win);
     }
 
-    addMessage(message) {
+    addMessage(message: string) {
         const msg = document.createElement("div");
         msg.classList.add("message");
 
         msg.innerText = message;
 
         const chat = this.main.getElementsByClassName("chat-history")[0];
+        if (!chat) throw Error("Element .chat-history not found");
+
         chat.appendChild(msg);
         chat.scrollTop = chat.scrollHeight;
     }
@@ -159,26 +161,33 @@ export class App {
                 <button type="submit">Login</button>
             </form>`;
 
-        win.getElementsByTagName("form")[0].addEventListener("submit", async event => {
+        const form = win.getElementsByTagName("form")[0];
+        if (!form) throw Error("Element <form> not found");
+
+        form.addEventListener("submit", async event => {
             event.preventDefault();
-            const form = event.target;
-            for (const e of form) {
+
+            for (const e of form.getElementsByTagName("button")) e.disabled = false;
+            for (const e of form.getElementsByTagName("input")) {
                 e.disabled = true;
                 e.removeAttribute("invalid");
             }
 
             try {
                 try {
-                    await this.login(form.account.value, form.domain.value, form.password.value);
+                    await this.login(form['account'].value, form['domain'].value, form['password'].value);
                 } finally {
                     for (const d of form.getElementsByTagName("div")) form.removeChild(d);
-                    for (const e of form) e.disabled = false;
+                    for (const e of form.getElementsByTagName("input")) e.disabled = false;
+                    for (const e of form.getElementsByTagName("button")) e.disabled = false;
                 }
             } catch (error) {
                 if (error.toString() === "Error: unable to authenticate") {
-                    document.getElementsByName("account")[0].setAttribute("invalid", "invalid");
+                    const account = document.getElementsByName("account")[0];
+                    if (account) account.setAttribute("invalid", "invalid");
                 } else {
-                    document.getElementsByName("domain")[0].setAttribute("invalid", "invalid");
+                    const domain = document.getElementsByName("domain")[0];
+                    if (domain) domain.setAttribute("invalid", "invalid");
                 }
 
                 const div = document.createElement("div");
@@ -190,18 +199,26 @@ export class App {
 
         this.windows.appendChild(win);
 
-        document.getElementsByName("domain")[0].addEventListener("input", (event) => {
-            event.target.removeAttribute("invalid");
+        const domain = document.getElementsByName("domain")[0];
+        if (!domain) throw Error("Element name=domain not found");
+
+        domain.addEventListener("input", (event) => {
+            domain.removeAttribute("invalid");
         });
 
-        document.getElementsByName("account")[0].addEventListener("input", (event) => {
-            event.target.removeAttribute("invalid");
+        const account = document.getElementsByName("account")[0];
+        if (!account) throw Error("Element name=account not found");
+
+        account.addEventListener("input", (event) => {
+            account.removeAttribute("invalid");
         });
 
-        document.getElementsByName("account")[0].focus();
+        account.focus();
     }
 
     setupMain() {
+        if (!this.session) throw Error("Invalid state");
+
         this.main.innerHTML = `
             <div class="chat">
                 <div class="chat-history"></div>
@@ -210,9 +227,13 @@ export class App {
                 </div>
             </div>`;
 
-        const input = document.getElementsByName("message")[0];
+        const input = document.getElementsByTagName("input")[0];
+        if (!input) throw Error("Element <input> not found");
+
         input.addEventListener("keyup", async event => {
             if (event.key === "Enter" && input.value.length > 0) {
+                if (!this.session) throw Error("No session found");
+
                 this.addMessage(input.value);
                 const val = input.value;
                 input.value = "";
diff --git a/src/main.ts b/src/main.ts
new file mode 100644
index 0000000..a07ad01
--- /dev/null
+++ b/src/main.ts
@@ -0,0 +1,11 @@
+"use strict";
+
+import * as Locutus from "./locutus";
+
+window.addEventListener("DOMContentLoaded", () => {
+    // Remove <noscript> tags
+    for (const noscript of document.getElementsByTagName("noscript")) {
+        noscript.remove();
+    }
+    new Locutus.App();
+});
diff --git a/www/res/js/modules/usimp.js b/src/usimp.ts
similarity index 72%
rename from www/res/js/modules/usimp.js
rename to src/usimp.ts
index d826f5d..eac50c1 100644
--- a/www/res/js/modules/usimp.js
+++ b/src/usimp.ts
@@ -1,16 +1,48 @@
 "use strict";
 
+interface DomainJson {
+    name: string,
+    id: string,
+}
+
+interface DomainServerJson {
+    host: string,
+    id: string,
+    priority: number,
+    weight: number,
+    protocols: {
+        https: number | undefined,
+        wss: number | undefined,
+        http: number | undefined,
+        ws: number | undefined,
+        udp: number | undefined
+    }
+}
+
+interface EventJson {
+    data: {
+        event: {
+            data: any
+        }
+    }
+}
+
+interface WellKnownJson {
+    domain: DomainJson,
+    domain_servers: DomainServerJson[]
+}
+
 export class Domain {
-    name;
-    id;
-    servers;
-    invalidServers;
+    name: string;
+    id: string;
+    servers: DomainServer[];
+    invalidServers: DomainServer[];
 
     toString() {
         return `[${this.name}]`;
     }
 
-    constructor(jsonData, domainServers) {
+    constructor(jsonData: DomainJson, domainServers: DomainServerJson[]) {
         // FIXME check values
         this.name = jsonData.name;
         this.id = jsonData.id;
@@ -21,7 +53,7 @@ export class Domain {
         this.invalidServers = [];
     }
 
-    static async fromName(domainName) {
+    static async fromName(domainName: string): Promise<Domain> {
         const controller = new AbortController();
         const timer = setTimeout(() => controller.abort(), 2000);
 
@@ -35,20 +67,20 @@ export class Domain {
             throw Error("Invalid response");
         }
 
-        const data = await response.json();
+        const data: WellKnownJson = await response.json();
         return new Domain(data.domain, data.domain_servers);
     }
 
-    chooseDomainServer() {
+    chooseDomainServer(): DomainServer {
         if (this.servers.length === 0) throw Error("No domain servers specified");
 
         const servers = this.servers.filter(srv => !this.invalidServers.map(srv => srv.id).includes(srv.id));
         if (servers.length === 0) throw Error("No domain servers reachable");
-        if (servers.length === 1) return servers[0];
+        if (servers.length === 1 && servers[0]) return servers[0];
 
         const priority = servers.reduce((min, srv) => Math.min(min, srv.priority), Infinity);
         const domainServers = servers.filter(srv => srv.priority === priority);
-        if (domainServers.length === 1) return servers[0];
+        if (domainServers.length === 1 && servers[0]) return servers[0];
 
         const totalWeight = domainServers.reduce((total, srv) => total + srv.weight, 0);
         const w = Math.floor(Math.random() * totalWeight);
@@ -64,18 +96,23 @@ export class Domain {
 }
 
 export class DomainServer {
-    host;
-    id;
-    priority;
-    weight;
-    protocols;
+    host: string;
+    id: string;
+    priority: number;
+    weight: number;
+    protocols: {
+        https: number | undefined,
+        wss: number | undefined,
+        http: number | undefined,
+        ws: number | undefined,
+        udp: number | undefined
+    };
 
     toString() {
         return `[${this.host}/${this.priority}/${this.weight}]`;
     }
 
-    constructor(jsonData) {
-        // FIXME check values
+    constructor(jsonData: DomainServerJson) {
         this.host = jsonData.host;
         this.id = jsonData.id;
         this.priority = jsonData.priority;
@@ -101,20 +138,24 @@ export class Event {
 }
 
 export class Session {
-    domain;
-    server;
-    token;
+    domain: Domain;
+    server: DomainServer | null;
+    token: string | null;
 
-    httpBaseUrl;
-    websocket;
-    numRequests;
+    httpBaseUrl: string | null;
+    websocket: WebSocket | null;
+    numRequests: number;
 
-    constructor(domain) {
+    constructor(domain: Domain) {
         this.domain = domain;
         this.numRequests = 0;
+        this.server = null;
+        this.token = null;
+        this.httpBaseUrl = null;
+        this.websocket = null;
     }
 
-    async chooseDomainServer() {
+    async chooseDomainServer(): Promise<{ http: number | null, ws: number | null } | undefined> {
         while (!this.server) {
             this.server = this.domain.chooseDomainServer();
 
@@ -128,7 +169,7 @@ export class Session {
             */
 
             // TODO http -> https
-            if ("http" in protocols) {
+            if (protocols) {
                 this.httpBaseUrl = `http://${host}:${protocols.http}/_usimp`;
                 try {
                     return await this.ping();
@@ -142,9 +183,10 @@ export class Session {
                 this.server = null;
             }
         }
+        return undefined;
     }
 
-    async send(endpoint, data, timeout = 2000, forceHttp = false) {
+    async send(endpoint: string, data: object, timeout: number = 2000, forceHttp: boolean = false) {
         this.numRequests++;
 
         if (!forceHttp && this.websocket) {
@@ -156,7 +198,7 @@ export class Session {
             const controller = new AbortController();
             const timer = setTimeout(() => controller.abort(), timeout);
 
-            let headers = {
+            let headers: Record<string, string> = {
                 'Content-Type': 'application/json',
                 'To-Domain': this.domain.id,
             };
@@ -175,7 +217,7 @@ export class Session {
             clearTimeout(timer);
 
             const responseData = await response.json();
-            responseData.duration = endTime - startTime;
+            responseData.duration = endTime.getUTCMilliseconds() - startTime.getUTCMilliseconds();
             return responseData;
         }
     }
@@ -193,7 +235,7 @@ export class Session {
         return result;
     }
 
-    async authenticate(accountName, password) {
+    async authenticate(accountName: string, password: string) {
         const response = await this.send("authenticate", {
             type: "password",
             name: accountName,
@@ -205,19 +247,19 @@ export class Session {
         return response;
     }
 
-    async sendEvent(roomId, data) {
+    async sendEvent(roomId: string, data: object) {
         return this.send("send_event", {
             room_id: roomId,
             data: data,
         });
     }
 
-    subscribe(func) {
+    subscribe(func: (a: EventJson) => void) {
         this.numRequests++;
         if (this.websocket) {
             // TODO
         } else {
-            let headers = {
+            let headers: Record<string, string> = {
                 'Content-Type': 'application/json',
                 'To-Domain': this.domain.id,
             };
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..748c608
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,71 @@
+{
+  "compilerOptions": {
+    /* Visit https://aka.ms/tsconfig.json to read more about this file */
+
+    /* Basic Options */
+    // "incremental": true,                         /* Enable incremental compilation */
+    "target": "ES2020",                                /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
+    "module": "es2020",                           /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
+    // "lib": [],                                   /* Specify library files to be included in the compilation. */
+    // "allowJs": true,                             /* Allow javascript files to be compiled. */
+    // "checkJs": true,                             /* Report errors in .js files. */
+    // "jsx": "preserve",                           /* Specify JSX code generation: 'preserve', 'react-native', 'react', 'react-jsx' or 'react-jsxdev'. */
+    // "declaration": true,                         /* Generates corresponding '.d.ts' file. */
+    // "declarationMap": true,                      /* Generates a sourcemap for each corresponding '.d.ts' file. */
+    // "sourceMap": true,                           /* Generates corresponding '.map' file. */
+    // "outFile": "./",                             /* Concatenate and emit output to single file. */
+    "outDir": "www/res/scripts",                              /* Redirect output structure to the directory. */
+    "rootDir": "src",                             /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
+    // "composite": true,                           /* Enable project compilation */
+    // "tsBuildInfoFile": "./",                     /* Specify file to store incremental compilation information */
+    // "removeComments": true,                      /* Do not emit comments to output. */
+    // "noEmit": true,                              /* Do not emit outputs. */
+    // "importHelpers": true,                       /* Import emit helpers from 'tslib'. */
+    // "downlevelIteration": true,                  /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
+    // "isolatedModules": true,                     /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
+
+    /* Strict Type-Checking Options */
+    "strict": true,                                 /* Enable all strict type-checking options. */
+    "noImplicitAny": true,                       /* Raise error on expressions and declarations with an implied 'any' type. */
+    "strictNullChecks": true,                    /* Enable strict null checks. */
+    "strictFunctionTypes": true,                 /* Enable strict checking of function types. */
+    "strictBindCallApply": true,                 /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
+    "strictPropertyInitialization": true,        /* Enable strict checking of property initialization in classes. */
+    "noImplicitThis": true,                      /* Raise error on 'this' expressions with an implied 'any' type. */
+    "alwaysStrict": true,                        /* Parse in strict mode and emit "use strict" for each source file. */
+
+    /* Additional Checks */
+    // "noUnusedLocals": true,                      /* Report errors on unused locals. */
+    // "noUnusedParameters": true,                  /* Report errors on unused parameters. */
+    "noImplicitReturns": true,                   /* Report error when not all code paths in function return a value. */
+    "noFallthroughCasesInSwitch": true,          /* Report errors for fallthrough cases in switch statement. */
+    "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
+    "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+
+    /* Module Resolution Options */
+    // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
+    // "baseUrl": "./",                             /* Base directory to resolve non-absolute module names. */
+    // "paths": {},                                 /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
+    // "rootDirs": [],                              /* List of root folders whose combined content represents the structure of the project at runtime. */
+    // "typeRoots": [],                             /* List of folders to include type definitions from. */
+    // "types": [],                                 /* Type declaration files to be included in compilation. */
+    // "allowSyntheticDefaultImports": true,        /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
+    "esModuleInterop": true,                        /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
+    // "preserveSymlinks": true,                    /* Do not resolve the real path of symlinks. */
+    // "allowUmdGlobalAccess": true,                /* Allow accessing UMD globals from modules. */
+
+    /* Source Map Options */
+    // "sourceRoot": "",                            /* Specify the location where debugger should locate TypeScript files instead of source locations. */
+    // "mapRoot": "",                               /* Specify the location where debugger should locate map files instead of generated locations. */
+    // "inlineSourceMap": true,                     /* Emit a single file with source maps instead of having a separate file. */
+    // "inlineSources": true,                       /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
+
+    /* Experimental Options */
+    // "experimentalDecorators": true,              /* Enables experimental support for ES7 decorators. */
+    // "emitDecoratorMetadata": true,               /* Enables experimental support for emitting type metadata for decorators. */
+
+    /* Advanced Options */
+    "skipLibCheck": true,                           /* Skip type checking of declaration files. */
+    "forceConsistentCasingInFileNames": true        /* Disallow inconsistently-cased references to the same file. */
+  }
+}
diff --git a/www/index.html b/www/index.html
index a8137cb..926f5a8 100644
--- a/www/index.html
+++ b/www/index.html
@@ -19,8 +19,10 @@ Distributed, end-to-end encrypted instant messaging."/>
     <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent"/>
     <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
     <link rel="icon" sizes="64x64" href="/favicon.ico" type="image/x-icon"/>
-    <link rel="stylesheet" href="/res/styles/styles.css?v=0.0.0-0" type="text/css"/>
-    <script src="/res/js/main.js?v=0.0.0-0" type="module"></script>
+    <link rel="stylesheet" href="/res/styles/styles.css?v=0.0.0+10" type="text/css"/>
+    <script type="module" src="/res/scripts/usimp.js?v=0.0.0+10"></script>
+    <script type="module" src="/res/scripts/locutus.js?v=0.0.0+10"></script>
+    <script type="module" src="/res/scripts/main.js?v=0.0.0+10"></script>
     <meta http-equiv="Content-Security-Policy" content="
         default-src 'none';
         style-src 'self';
diff --git a/www/res/js/main.js b/www/res/js/main.js
deleted file mode 100644
index 1766fa6..0000000
--- a/www/res/js/main.js
+++ /dev/null
@@ -1,9 +0,0 @@
-"use strict";
-
-import * as Locutus from "./modules/locutus.js";
-
-window.addEventListener("DOMContentLoaded", () => {
-    // Remove <noscript> tag
-    document.getElementsByTagName("noscript")[0].remove();
-    new Locutus.App();
-});