Cookies are small text files placed on your device by websites you visit. They are widely used to make websites work efficiently, improve the user experience, and provide information to site owners.
Cookies can be session cookies (deleted when you close your browser) or persistent cookies (remain on your device for a set period, or until deleted manually).
We also use similar technologies such as local storage and session storage to remember your expression history and UI preferences — these work like cookies but are stored differently in your browser.
EXPR evaluates all expressions locally in your browser. Your expressions are never sent to our servers and are not accessible via any cookie or tracking technology.
We categorise the cookies we use into four types. Each category serves a distinct purpose:
Below is a list of the specific cookies we set, what they do, and how long they last:
| Name | Category | Purpose | Duration |
|---|---|---|---|
expr_session |
Necessary | Maintains your current session state | Session |
expr_csrf |
Necessary | Cross-site request forgery protection token | Session |
expr_cookie_prefs |
Necessary | Stores your cookie consent preferences | 1 year |
_expr_analytics |
Analytics | Tracks page views and feature interactions (anonymised) | 13 months |
_expr_visit |
Analytics | Distinguishes new vs. returning visitors | 30 minutes |
expr_history |
Functional | Stores your recent expression evaluation history locally | Persistent (localStorage) |
expr_prefs |
Functional | Saves display and UI preferences | 1 year |
Use the toggles in the Types We Use section above to update your cookie preferences at any time. Your choices are saved in a cookie named expr_cookie_prefs and applied on your next visit.
Withdrawing consent for a category of cookies does not affect the lawfulness of processing carried out before you withdrew consent.
Strictly necessary cookies cannot be disabled as they are required for the site to function. All other categories are optional and off by default in regions where consent is legally required.
You can also control cookies at the browser level. Each browser provides different controls:
Note that blocking all cookies may prevent parts of the EXPR website from working correctly — in particular, form submissions and your expression history may be affected.
To opt out of analytics tracking across the web, you may also install a browser extension such as uBlock Origin or use a privacy-focused browser.
We may update this Cookie Policy as we add new features or as legal requirements change. When material changes are made, we will update the "Last updated" date and, where required by law, ask for your consent again.
We recommend reviewing this page periodically. The most current version is always available at expr.dev/cookies.
If you have questions about our use of cookies or this policy, please contact us:
For more information about how we handle personal data in general, see our Privacy Policy.