Functional cookies store your preferences so a website can remember them between pages or visits. They handle things like your chosen language, your region, whether you dismissed a notification, and similar choices that make the site feel personalised. Without them, every page load starts from scratch.
They sit in a grey area between strictly necessary cookies (which the site cannot function without) and tracking cookies (which monitor your behaviour for analytics or advertising). That distinction matters because it determines whether you need consent to set them.
How Functional Cookies Work
When your browser loads a page, the server can include a Set-Cookie header in its response. The browser stores that cookie and sends it back with every subsequent request to the same domain. That round-trip is the entire mechanism - nothing more exotic than a small text file bouncing back and forth.
Functional cookies are almost always first-party, meaning they are set by the domain you are actually visiting. A cookie set by example.com is only sent back to example.com, not to any other site. This is what separates them from third-party tracking cookies that follow you around the web.
They come in two flavours:
- Session cookies - deleted automatically when you close the browser. Useful for temporary state like a media player's volume level.
- Persistent cookies - stored until their expiry date, which might be 30 days, a year, or longer. Language preferences typically use persistent cookies so the site remembers your choice across visits.
A typical e-commerce site might set 5-15 functional cookies. A simple brochure site might set none at all. The count depends entirely on what features the site offers.
Common Examples of Functional Cookies
Language and Region Preferences
Multilingual sites rely heavily on functional cookies. WordPress sites using Polylang store your language selection in pll_language. WPML uses _icl_current_language. Shopify stores the locale in a locale cookie. Without these, a French-speaking visitor would see the default language on every new page.
Region cookies work the same way. An international retailer might store your country code so it can show local pricing, VAT rates, and shipping options without asking you each time.
Login and Authentication State
This is where the line between "necessary" and "functional" gets blurry. A session cookie like PHPSESSID or Laravel's laravel_session is strictly necessary - the application cannot process authenticated requests without it. But a "remember me" token (remember_web_* in Laravel, wordpress_logged_in_* in WordPress) is a convenience feature. It keeps you signed in for days or weeks so you do not have to re-enter your password.
Most privacy regulators treat session cookies as necessary and "remember me" cookies as functional. The practical difference: session cookies do not need consent; remember-me cookies usually do.
User Interface Customisation
Dark mode preferences, font size adjustments, sidebar collapsed/expanded state, and accessibility settings are all stored in functional cookies. Some sites use a single preferences cookie containing a JSON string with multiple settings. Others set individual cookies for each choice.
Cookie banner "dismissed" flags also fall here. When a visitor closes a notification bar, the site sets a cookie to prevent showing it again. The banner itself might be about cookies, which creates an amusingly recursive situation - but it is still a functional cookie by definition.
Media Player and Form Preferences
Video players remember your volume and quality settings between pages. YouTube embeds store these in first-party cookies (though YouTube also sets plenty of marketing cookies alongside them). Live chat widgets remember whether the chat window is open or minimised, and may store your name if you entered it previously.
Partially filled forms are another case. Some e-commerce checkouts save your progress in a cookie so you do not lose your shipping details if you navigate away and come back.
Shopping Cart and Wishlist Persistence
For logged-out visitors, the shopping cart often lives in a cookie or is referenced by a cookie ID pointing to server-side storage. "Recently viewed items" and wishlist features work the same way.
Note the distinction: a transactional cart cookie that exists only during checkout is often classified as necessary (the user explicitly requested the checkout service). A persistent cart that remembers items for days is functional - it is a convenience, not a requirement.
Functional Cookies vs Other Cookie Types
| Type | Purpose | Consent Required? | Example |
|---|---|---|---|
| Necessary | Core site operation | No (GDPR exempt) | Session ID, CSRF token |
| Functional | User preferences & convenience | Usually yes | Language, dark mode |
| Analytics | Usage measurement & reporting | Yes | _ga, _gid |
| Marketing | Ad targeting & tracking | Yes | _fbp, _gcl_au |
The boundaries are not always clean. A cookie that stores your selected currency could be necessary (the checkout breaks without it) or functional (the site has a sensible default). Classification depends on actual behaviour, not the cookie's name or what the developer intended. When in doubt, ask: "Would the specific feature the user requested still work without this cookie?" If yes, it is probably functional rather than necessary.
Do Functional Cookies Need Consent?
GDPR and the ePrivacy Directive
Article 5(3) of the ePrivacy Directive sets a two-part test for the consent exemption. A cookie is exempt only if it is (1) strictly necessary for (2) a service the user explicitly requested. A language preference cookie fails this test - the user requested a web page, not a language-remembering service. So under EU law, most functional cookies need informed, prior consent.
The GDPR adds requirements about how that consent must be obtained: freely given, specific, informed, and unambiguous. Pre-ticked boxes do not count. Bundled consent (accepting all cookies in one click without granular control) is questionable. A proper consent banner should let visitors accept or reject functional cookies separately from analytics and marketing.
CCPA / CPRA (California)
California uses an opt-out model rather than opt-in. Functional cookies are generally fine unless they involve "selling" or "sharing" personal information with third parties. In practice, first-party functional cookies rarely trigger CCPA obligations because the data stays with the site operator. But if a third-party service sets a functional cookie that also enables cross-site profiling, you are back in regulated territory.
UK GDPR and PECR
The UK mirrors the EU approach. The ICO's guidance is clear: preference cookies that are not strictly necessary require consent. The Privacy and Electronic Communications Regulations (PECR) apply the same Article 5(3)-style test as the ePrivacy Directive.
Other Jurisdictions
Brazil's LGPD, Canada's PIPEDA, and South Africa's POPIA all require some form of legal basis for processing personal data via cookies. The mechanisms vary - LGPD allows legitimate interest as a basis in some cases, PIPEDA uses a "reasonable person" standard - but the trend is consistent: non-essential cookies need either consent or a strong justification.
For a deeper look at how these laws affect your cookie banner, see our features page where we cover geo-detection and region-specific rules.
How to Manage Functional Cookies on Your Website
Step 1: Scan Your Website for Cookies
You cannot manage what you have not measured. A cookie scan crawls your site, loads each page in a real browser, and records every cookie that gets set - including HttpOnly cookies invisible to JavaScript and third-party cookies from embedded services. Many site owners are surprised to discover cookies they did not know existed, set by plugins, tag managers, or embedded widgets.
Kukie.io's scanner does exactly this. It detects first-party and third-party cookies, identifies their origin, and flags ones that need categorisation. You can start a free scan to see what your site is setting right now.
Step 2: Categorise Each Cookie Accurately
Do not dump everything into "functional" to sidestep consent requirements. Regulators specifically look for this pattern - the French CNIL and the Irish DPC have both fined companies for misclassifying analytics cookies as functional. Each cookie needs individual review: what data does it store, who sets it, and what happens if the visitor opts out?
A good consent management platform will suggest categories based on known cookie databases, but always verify. A cookie named _prefs could store language preferences (functional) or could track page views (analytics). Only the actual behaviour matters.
Step 3: Configure Your Consent Banner
Your banner should offer granular control. Visitors should be able to accept functional cookies while rejecting analytics and marketing, or vice versa. A single "Accept All" button with no alternatives does not meet GDPR requirements for freely given consent.
The banner also needs to explain what each category does in plain language - not legal boilerplate. Check our pricing page to see what Kukie.io offers for managing this.
Step 4: Block Functional Cookie Scripts Until Consent
Setting the cookie after consent is not enough if the script that sets it has already executed and sent data somewhere. Proper consent management blocks the script entirely until the visitor makes a choice. For functional cookies, this means features like live chat widgets, language selectors powered by third-party services, or embedded media players should not load until the visitor allows them.
Kukie.io handles this with automatic script blocking - it detects known third-party scripts and prevents them from executing until the relevant cookie category is accepted.
Step 5: Keep Your Cookie Audit Up to Date
Cookies change every time you update a plugin, switch themes, add a new embed, or modify your tag manager configuration. A scan from six months ago may be missing half the cookies your site sets today. Schedule regular re-scans - monthly is a good baseline for active sites, quarterly for static ones.
Frequently Asked Questions
Are functional cookies the same as necessary cookies?
No. Necessary cookies (also called strictly necessary or essential cookies) are required for a website to function at all - they handle things like session management and security tokens. Functional cookies enhance the experience by remembering preferences like language or region, but the site would still work without them.Do functional cookies require consent under GDPR?
It depends on the specific cookie. If a functional cookie is strictly necessary for a service the user explicitly requested (such as remembering items in a shopping cart), consent may not be required. However, most functional cookies - like remembering language preferences or font size - do require informed consent under GDPR and the ePrivacy Directive because they are not essential for delivering the requested service.Can functional cookies track users across websites?
Functional cookies set by the website you are visiting (first-party) do not track you across other sites. However, some third-party services embedded on a site may set cookies labelled as functional that could have broader tracking capabilities. This is why reviewing your cookie audit results and categorising cookies accurately matters.What happens if a visitor rejects functional cookies?
The website will still work, but certain personalised features may reset on every visit. For example, the visitor might need to re-select their language each time, see default region settings instead of localised content, or lose the contents of a persistent shopping cart.How do I identify functional cookies on my website?
Run a cookie scan using a tool like Kukie.io. It will detect all cookies set by your site and its third-party scripts. Cookies that store user preferences, UI settings, or session choices - without performing analytics or advertising functions - typically fall into the functional category.Do functional cookies expire?
Yes. Functional cookies can be either session cookies (deleted when the browser closes) or persistent cookies (stored until a set expiry date). A language preference cookie, for example, might persist for 30 days or a year, while a session-based cookie for a media player volume setting would disappear when the tab closes.Take Control of Your Cookie Compliance
If you are not sure which cookies your site sets, start with a free scan. Kukie.io detects, categorises, and helps you manage every cookie - so your visitors get a clear choice, and you stay on the right side of the law.
