Privacy Policy
Last updated: June 7, 2026
This policy explains how CostNest handles data when you use our calculators and visit our site. The short version: our calculators process everything locally in your browser — we never see your inputs. The longer version is below.
1. Browser-Based Calculations — Your Data Never Leaves Your Device
At CostNest, privacy is built into our code. All calculator inputs are processed entirely within your web browser using local JavaScript execution. No calculation values, financial figures, or inputs you enter are ever transmitted to CostNest servers or stored externally. We do not require accounts, email addresses, or any personally identifiable information to use any calculator on this site.
2. Google Advertising & Personalisation Cookies
We display advertisements through Google AdSense (publisher ID declared in our ads.txt file). Google uses advertising cookies — including IDE, DSID, FLC, AID, and TAID — to serve ads based on your interests and prior browsing activity. These cookies are set by Google's advertising platform (doubleclick.net and googlesyndication.com domains), not by CostNest directly. For visitors in the EU, EEA, and UK, our consent banner is shown before any personalised advertising cookies are set, in full compliance with GDPR and Google's EU User Consent Policy. You may withdraw consent at any time by clicking the cookie settings button in the site footer. To opt out of interest-based advertising globally, visit Google's Ad Settings at https://adssettings.google.com or the Network Advertising Initiative opt-out page at https://optout.aboutads.info/. Opting out means you may still see ads, but they will not be personalised to your browsing history.
3. Google Analytics
We use Google Analytics (tracking ID: G-B6LYMPHCXG) to understand aggregate site usage — which pages are visited, session duration, device type, and traffic sources. This data is anonymised and aggregated before it reaches us. No personally identifiable information is collected by Google Analytics. IP anonymisation is enabled. You can opt out using the Google Analytics Opt-out Browser Add-on available at https://tools.google.com/dlpage/gaoptout.
4. Vercel Analytics
We use Vercel Analytics to collect Core Web Vitals and page view data to improve site performance. Vercel Analytics does not use cookies and does not collect personal data — it measures performance metrics such as page load speed, layout stability (CLS), and interaction latency (INP). No personally identifiable information is processed.
5. Contact Form Data
When you use our contact form, your name, email address, subject line, and message are submitted to Formspree (formspree.io) and forwarded to our email. Formspree stores submissions for up to 30 days under their own privacy policy. We do not share your contact form data with any third party. You may request deletion of your submission by emailing contact@costnest.site.
6. Cookies Summary
Cookies used on CostNest: (1) _ga and _ga_XXXXXX — Google Analytics session cookies, 2-year expiry, set only after consent. (2) Google Advertising cookies (IDE, DSID, FLC, AID, TAID) — set by Google to serve and personalise ads, set only after consent. (3) costnest_cookie_consent — stores your consent preference in localStorage, no server transmission, no expiry. All calculator inputs remain in your browser session only and are never transmitted.
7. Server Log Files
Like most web hosting platforms, CostNest's infrastructure provider (Vercel) collects standard server access logs including IP addresses, browser type, ISP, date/time stamps, and referring pages. This data is used exclusively for security monitoring and performance analysis and is not linked to personally identifiable information. Logs are retained according to Vercel's data retention policy.
8. Children's Privacy
CostNest does not knowingly collect personally identifiable information from children under 13. Our calculators are general-purpose financial and utility tools not directed at children. If you believe a child under 13 has submitted personal data via our contact form, please contact us immediately at contact@costnest.site.
9. Your Data Rights
You have the right to access, correct, or request deletion of any personal data we hold (contact form submissions only — calculator inputs are never stored). To exercise your rights, use our contact form or email contact@costnest.site. We will respond within 30 days. EU/UK residents have additional rights under GDPR including the right to data portability, the right to restrict processing, and the right to lodge a complaint with a supervisory authority.
10. Changes to This Policy
We may update this Privacy Policy to reflect changes in our services, advertising vendors, or applicable law. When we do, we update the 'Last Updated' date below. Continued use of CostNest after any changes constitutes acceptance of the updated policy. Material changes affecting your rights will be notified via a banner on the site.