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Introducing: The Async Cookie Store API

- 5 min read

TLDR: The Cookie Store API is a new browser API built to expose cookies to service worker and offer an asynchronous alternative to document.cookie. It’s available in Chrome Browser starting from version 87.

Are you sick and tired of weird ways to get cookies from document.cookie ? Hate it that you don’t know whether the cookie you set was actually saved or not? Introducing: Cookie Store API, available on Chrome version 87!



We all use HTTP Cookies almost daily, but working with them was never an easy task.
The cookies interface is overly complexed and contains performance issues.
Saving all of the cookies in document.cookie which is part of the Document Object Model from October 2000, seems like a pattern that doesn’t correspond to the javascript we write these days.

The Cookie Store API aims to improve this by providing an asynchronous alternative to document.cookie and exposing HTTP cookies to service workers, which will also benefit performance. It’s available on Chrome Browser starting from version 87 but still didn’t land in any other major browsers.

Get Cookies

Getting a cookie always looked odd to me. Why do I have a full string containing all of the cookies? Getting a specific cookie always seems like an over-complex solution, using some regex or looping over the document.cookie value.
In fact, all of us who need cookies probably have this util taken from some StackOverflow answer in their codebase:

function getCookie(name) { var nameEQ = name + "="; var ca = document.cookie.split(";"); for (var i = 0; i < ca.length; i++) { var c = ca[i]; while (c.charAt(0) == " ") c = c.substring(1, c.length); if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length, c.length); } return null; } const cookie = getCookie("opted-out");

In the new way, all we need to do is use the cookieStore object and call its get function. Don’t forget that this returns a promise so you await for its result and if something wrong happened, it would throw an error:

try { const cookie = await cookieStore.get("opted-out"); if (cookie) { console.log(`Found ${} cookie: ${cookie.value}`); } else { console.log("Cookie not found"); } } catch (e) { console.error(`Cookie store error: ${e}`); }

No more looping over a cookies string! Amazing!

Set Cookie

Don't you just hate setting a cookie? The API seems so old-fashioned.

document.cookie = `opted-out=true; Expires=${ + onde_day_ms }; domain:`;

Following what we wrote about getting cookies, the setCookie util probably looks somewhat like this:

function setCookie(name, value, days) { var expires = ""; if (days) { var date = new Date(); date.setTime(date.getTime() + days * 24 * 60 * 60 * 1000); expires = "; expires=" + date.toUTCString(); } document.cookie = name + "=" + (value || "") + expires + "; path=/"; }

After doing that, we’d probably also want to know that the cookie was successfully created. So we’ll use the getCookie util from before and loop over the cookies string to find that cookie.

In the new API, what you’ll need to do is use the cookieStore object and call the set function with the params, that’s all.

try { await cookieStore.set({ name: "opted-out", value: true, expiers: + one_day_ms, domain: "", }); } catch (e) { console.error(`Failed to set cookie: ${e}`); }

After calling that function, as long as we didn’t get to the catch block, we can be 100% sure that the cookie was saved successfully, and we don’t need to loop over anything or call cookieStore.get to see that it was saved.

Delete Cookies

To delete the cookie, we probably had something similar to this util:

function deleteCookie(name) { document.cookie = name + "=; Path=/; Expires=Thu, 01 Jan 1970 00:00:01 GMT;"; }

It will basically set the cookie date to an old date and count on the browser to delete it since it’s already expired.

In the new way, you’ll need to call the delete function:

try { await cookieStore.delete("opted-out"); } catch (e) { console.error(`Failed to delete cookie: ${e}`); }

Once again, as long as we didn’t get to the catch block, you can 100% be sure that the delete happened.

Monitoring Cookies

A cool thing you can do with the new Cookie Store API is know when the cookie object was changed and act on it:

cookieStore.addEventListener("change", (event) => { console.log(`${event.changed.length} changed cookies`); for (const cookie in event.changed) { console.log(`Cookie ${} changed to ${cookie.value}`); } console.log(`${event.deleted.length} deleted cookies`); for (const cookie in event.deleted) { console.log(`Cookie ${} deleted`); } });


It looks like the Chrome team tackled a problem we took for granted for a long time, and I do believe that this is great progress towards a better web!
If you’d like to read more, you can visit the Cookie Store API Draft.

Feel free to ask me any question, I'm available on twitter.

Hope you enjoyed!
— Matan.