FAQs »

How do I manually set a cookie in a script?

Simply put, cookies are a way to convey state in the otherwise stateless HTTP protocol. Many sites use them to store and relay information about the user from one request to the next.

Once a cookie is set, the client or browser is expected to send that cookie with every subsequent request to that same server (sometimes only to certain paths).

Cookies are normally set by the Set-Cookie header, but they can also be set by JavaScript. You can read more about the Cookie header on the Mozilla Developer Network.

Setting cookies in protocol scripts

In most cases, it’s not necessary to manually set a Cookie header in a protocol script. Loadster automatically receives Set-Cookie headers from your server and handles the cookies like any other HTTP user agent.

However, if you need to manually pass a cookie from your script that was not received from the server, here is how you would do it.

First of all, click the Add… menu on the step you want to add the cookie for, and choose Add request header.

Adding a custom header
Adding a custom header

Enter the header name of “Cookie” and the header value as the key-value pair. For this example, we’ll go with a cookie name of “a” and a value of “1”.

Setting a Cookie header
Setting a Cookie header

After playing your script, you’ll see a message about the custom request header in the logs:

The custom Cookie header appears in the logs
The custom Cookie header appears in the logs

You can also drill into the request to view the exact headers that were sent:

The custom Cookie header appears in the results tree
The custom Cookie header appears in the results tree

Setting cookies in browser scripts

Browser Bots automate real web browsers. Since the browser handles cookies automatically, and in most cases you don’t need to worry about setting them yourself.

However, there are times you might want to set a cookie manually. For example, you might be testing a site that requires login, but you’re not actually performing the login in the script. Instead you could manually set the cookies that you’d otherwise get by logging in.

One way to accomplish this in a browser script is with an evaluate block. Evaluate blocks let you execute custom JavaScript inside the bot’s browser.

An evaluate block that sets a cookie would go something like this:

// Declare a function that sets a cookie
function setCookie(cookieName, cookieValue, expiresInDays) {
  const date = new Date();
  const expiresInMillis = expiresInDays * 86400000;

  date.setTime(date.getTime() + expiresInMillis);

  document.cookie = cookieName + '=' + cookieValue + ';expires=' + date.toUTCString() + ';path=/';

// Call the function to actually set a cookie
setCookie('myCookieName', 'myCookieValue', 10)

Of course, you can call the function multiple times if you need to set multiple cookies.