Cookies - Bun

Bun provides two native APIs for working with HTTP cookies: Bun.Cookie and Bun.CookieMap. They parse, generate, and manipulate cookies in HTTP requests and responses.

CookieMap class

Bun.CookieMap is a Map-like collection of cookies. It implements Iterable, so it works with for...of loops and the other iteration methods.

cookies.ts

// Empty cookie map
const cookies = new Bun.CookieMap();

// From a cookie string
const cookies1 = new Bun.CookieMap("name=value; foo=bar");

// From an object
const cookies2 = new Bun.CookieMap({
  session: "abc123",
  theme: "dark",
});

// From an array of name/value pairs
const cookies3 = new Bun.CookieMap([
  ["session", "abc123"],
  ["theme", "dark"],
]);

In HTTP servers

In Bun’s HTTP server, the cookies property on the request object (in routes) is an instance of CookieMap:

server.ts

const server = Bun.serve({
  routes: {
    "/": req => {
      // Access request cookies
      const cookies = req.cookies;

      // Get a specific cookie
      const sessionCookie = cookies.get("session");
      if (sessionCookie != null) {
        console.log(sessionCookie);
      }

      // Check if a cookie exists
      if (cookies.has("theme")) {
        // ...
      }

      // Set a cookie, it will be automatically applied to the response
      cookies.set("visited", "true");

      return new Response("Hello");
    },
  },
});

console.log("Server listening at: " + server.url);

Methods

`get(name: string): string | null`

Retrieves a cookie by name. Returns null if the cookie doesn’t exist.

get-cookie.ts

// Get by name
const cookie = cookies.get("session");

if (cookie != null) {
  console.log(cookie);
}

`has(name: string): boolean`

Checks if a cookie with the given name exists.

has-cookie.ts

// Check if cookie exists
if (cookies.has("session")) {
  // Cookie exists
}

`set(name: string, value: string): void`

`set(options: CookieInit): void`

Adds or updates a cookie in the map. Cookies default to { path: "/", sameSite: "lax" }.

set-cookie.ts

// Set by name and value
cookies.set("session", "abc123");

// Set using options object
cookies.set({
  name: "theme",
  value: "dark",
  maxAge: 3600,
  secure: true,
});

// Set using Cookie instance
const cookie = new Bun.Cookie("visited", "true");
cookies.set(cookie);

`delete(name: string): void`

`delete(options: CookieStoreDeleteOptions): void`

Removes a cookie from the map. When applied to a Response, this adds a cookie with an empty string value and an expiry date in the past. The browser only deletes the cookie if the domain and path match the ones it was created with.

delete-cookie.ts

// Delete by name using default domain and path.
cookies.delete("session");

// Delete with domain/path options.
cookies.delete({
  name: "session",
  domain: "example.com",
  path: "/admin",
});

`toJSON(): Record<string, string>`

Converts the cookie map to a serializable format.

cookie-to-json.ts

const json = cookies.toJSON();

`toSetCookieHeaders(): string[]`

Returns an array of values for Set-Cookie headers that apply all cookie changes. Use this with HTTP servers other than Bun.serve(). In Bun.serve(), you don’t need to call it: any changes made to the req.cookies map are automatically applied to the response headers.

node-server.js

import { createServer } from "node:http";
import { CookieMap } from "bun";

const server = createServer((req, res) => {
  const cookieHeader = req.headers.cookie || "";
  const cookies = new CookieMap(cookieHeader);

  cookies.set("view-count", Number(cookies.get("view-count") || "0") + 1);
  cookies.delete("session");

  res.writeHead(200, {
    "Content-Type": "text/plain",
    "Set-Cookie": cookies.toSetCookieHeaders(),
  });
  res.end(`Found ${cookies.size} cookies`);
});

server.listen(3000, () => {
  console.log("Server running at http://localhost:3000/");
});

Iteration

CookieMap provides several methods for iteration:

iterate-cookies.ts

// Iterate over [name, cookie] entries
for (const [name, value] of cookies) {
  console.log(`${name}: ${value}`);
}

// Using entries()
for (const [name, value] of cookies.entries()) {
  console.log(`${name}: ${value}`);
}

// Using keys()
for (const name of cookies.keys()) {
  console.log(name);
}

// Using values()
for (const value of cookies.values()) {
  console.log(value);
}

// Using forEach
cookies.forEach((value, name) => {
  console.log(`${name}: ${value}`);
});

Properties

`size: number`

Returns the number of cookies in the map.

cookie-size.ts

console.log(cookies.size); // Number of cookies

Bun.Cookie represents an HTTP cookie with its name, value, and attributes.

cookie-class.ts

import { Cookie } from "bun";

// Create a basic cookie
const cookie = new Bun.Cookie("name", "value");

// Create a cookie with options
const secureSessionCookie = new Bun.Cookie("session", "abc123", {
  domain: "example.com",
  path: "/admin",
  expires: new Date(Date.now() + 86400000), // 1 day
  httpOnly: true,
  secure: true,
  sameSite: "strict",
});

// Parse from a cookie string
const parsedCookie = new Bun.Cookie("name=value; Path=/; HttpOnly");

// Create from an options object
const objCookie = new Bun.Cookie({
  name: "theme",
  value: "dark",
  maxAge: 3600,
  secure: true,
});

Constructors

constructors.ts

// Basic constructor with name/value
new Bun.Cookie(name: string, value: string);

// Constructor with name, value, and options
new Bun.Cookie(name: string, value: string, options: CookieInit);

// Constructor from cookie string
new Bun.Cookie(cookieString: string);

// Constructor from cookie object
new Bun.Cookie(options: CookieInit);

Properties

cookie-properties.ts

cookie.name; // string - Cookie name
cookie.value; // string - Cookie value
cookie.domain; // string | null - Domain scope (null if not specified)
cookie.path; // string - URL path scope (defaults to "/")
cookie.expires; // number | undefined - Expiration timestamp (ms since epoch)
cookie.secure; // boolean - Require HTTPS
cookie.sameSite; // "strict" | "lax" | "none" - SameSite setting
cookie.partitioned; // boolean - Whether the cookie is partitioned (CHIPS)
cookie.maxAge; // number | undefined - Max age in seconds
cookie.httpOnly; // boolean - Accessible only via HTTP (not JavaScript)

Methods

`isExpired(): boolean`

Checks if the cookie has expired.

is-expired.ts

// Expired cookie (Date in the past)
const expiredCookie = new Bun.Cookie("name", "value", {
  expires: new Date(Date.now() - 1000),
});
console.log(expiredCookie.isExpired()); // true

// Valid cookie (Using maxAge instead of expires)
const validCookie = new Bun.Cookie("name", "value", {
  maxAge: 3600, // 1 hour in seconds
});
console.log(validCookie.isExpired()); // false

// Session cookie (no expiration)
const sessionCookie = new Bun.Cookie("name", "value");
console.log(sessionCookie.isExpired()); // false

`serialize(): string`

`toString(): string`

Returns a string representation of the cookie suitable for a Set-Cookie header.

serialize-cookie.ts

const cookie = new Bun.Cookie("session", "abc123", {
  domain: "example.com",
  path: "/admin",
  expires: new Date(Date.now() + 86400000),
  secure: true,
  httpOnly: true,
  sameSite: "strict",
});

console.log(cookie.serialize());
// => "session=abc123; Domain=example.com; Path=/admin; Expires=Sun, 19 Mar 2025 15:03:26 GMT; Secure; HttpOnly; SameSite=strict"
console.log(cookie.toString());
// => "session=abc123; Domain=example.com; Path=/admin; Expires=Sun, 19 Mar 2025 15:03:26 GMT; Secure; HttpOnly; SameSite=strict"

`toJSON(): CookieInit`

Converts the cookie to a plain object suitable for JSON serialization.

cookie-json.ts

const cookie = new Bun.Cookie("session", "abc123", {
  secure: true,
  httpOnly: true,
});

const json = cookie.toJSON();
// => {
//   name: "session",
//   value: "abc123",
//   path: "/",
//   secure: true,
//   httpOnly: true,
//   sameSite: "lax",
//   partitioned: false
// }

// Works with JSON.stringify
const jsonString = JSON.stringify(cookie);

Static methods

Parses a cookie string into a Cookie instance.

parse-cookie.ts

const cookie = Bun.Cookie.parse("name=value; Path=/; Secure; SameSite=Lax");

console.log(cookie.name); // "name"
console.log(cookie.value); // "value"
console.log(cookie.path); // "/"
console.log(cookie.secure); // true
console.log(cookie.sameSite); // "lax"

Factory method to create a cookie.

cookie-from.ts

const cookie = Bun.Cookie.from("session", "abc123", {
  httpOnly: true,
  secure: true,
  maxAge: 3600,
});

Types

types.ts

interface CookieInit {
  name?: string;
  value?: string;
  domain?: string;
  /** Defaults to '/'. To allow the browser to set the path, use an empty string. */
  path?: string;
  expires?: number | Date | string;
  secure?: boolean;
  /** Defaults to `lax`. */
  sameSite?: CookieSameSite;
  httpOnly?: boolean;
  partitioned?: boolean;
  maxAge?: number;
}

interface CookieStoreDeleteOptions {
  name: string;
  domain?: string | null;
  path?: string;
}

interface CookieStoreGetOptions {
  name?: string;
  url?: string;
}

type CookieSameSite = "strict" | "lax" | "none";

class Cookie {
  constructor(name: string, value: string, options?: CookieInit);
  constructor(cookieString: string);
  constructor(cookieObject?: CookieInit);

  readonly name: string;
  value: string;
  domain?: string;
  path: string;
  expires?: Date;
  secure: boolean;
  sameSite: CookieSameSite;
  partitioned: boolean;
  maxAge?: number;
  httpOnly: boolean;

  isExpired(): boolean;

  serialize(): string;
  toString(): string;
  toJSON(): CookieInit;

  static parse(cookieString: string): Cookie;
  static from(name: string, value: string, options?: CookieInit): Cookie;
}

class CookieMap implements Iterable<[string, string]> {
  constructor(init?: string[][] | Record<string, string> | string);

  get(name: string): string | null;

  toSetCookieHeaders(): string[];

  has(name: string): boolean;
  set(name: string, value: string, options?: CookieInit): void;
  set(options: CookieInit): void;
  delete(name: string): void;
  delete(options: CookieStoreDeleteOptions): void;
  delete(name: string, options: Omit<CookieStoreDeleteOptions, "name">): void;
  toJSON(): Record<string, string>;

  readonly size: number;

  entries(): IterableIterator<[string, string]>;
  keys(): IterableIterator<string>;
  values(): IterableIterator<string>;
  forEach(callback: (value: string, key: string, map: CookieMap) => void): void;
  [Symbol.iterator](): IterableIterator<[string, string]>;
}

​CookieMap class

​In HTTP servers

​Methods

​get(name: string): string | null

​has(name: string): boolean

​set(name: string, value: string): void

​set(options: CookieInit): void

​set(cookie: Cookie): void

​delete(name: string): void

​delete(options: CookieStoreDeleteOptions): void

​toJSON(): Record<string, string>

​toSetCookieHeaders(): string[]

​Iteration

​Properties

​size: number

​Cookie class

​Constructors

​Properties

​Methods

​isExpired(): boolean

​serialize(): string

​toString(): string

​toJSON(): CookieInit

​Static methods

​Cookie.parse(cookieString: string): Cookie

​Cookie.from(name: string, value: string, options?: CookieInit): Cookie

​Types

CookieMap class

In HTTP servers

Methods

`get(name: string): string | null`

`has(name: string): boolean`

`set(name: string, value: string): void`

`set(options: CookieInit): void`

`set(cookie: Cookie): void`

`delete(name: string): void`

`delete(options: CookieStoreDeleteOptions): void`

`toJSON(): Record<string, string>`

`toSetCookieHeaders(): string[]`

Iteration

Properties

`size: number`

Cookie class

Constructors

Properties

Methods

`isExpired(): boolean`

`serialize(): string`

`toString(): string`

`toJSON(): CookieInit`

Static methods

`Cookie.parse(cookieString: string): Cookie`

`Cookie.from(name: string, value: string, options?: CookieInit): Cookie`

Types