Privacy Policy
Last updated: September 9, 2026
The short version: the HTML file you check is never uploaded anywhere — everything happens locally in your browser. A short check history is saved on your own device so you can revisit past results. We use a privacy-friendly, cookie-free analytics service to count anonymous page visits.
What SEOCHECKER is
Synthlucida SEOCHECKER ("SEOCHECKER", "we", "the tool") is a free tool published by SYNTHLUCIDA that checks an HTML file you choose and reports on common SEO signals. This page explains, in plain language, what happens to your data when you use it.
Your file stays on your device
When you choose a file and click "Check", SEOCHECKER reads and analyzes it entirely inside your browser using standard web technologies (the browser's own HTML parser). The file is never uploaded, transmitted, or sent to any server — SEOCHECKER doesn't even need an internet connection to perform the check itself. No one but you ever sees the file or the result, unless you choose to export it or share it yourself.
Information stored locally in your browser
For convenience, SEOCHECKER saves a small amount of information directly on your device, using your browser's local storage. None of this is ever transmitted to us or to anyone else — it stays on your device and you can clear it at any time (using the in-app "Clear history" button, or by clearing your browser's site data).
- Check history — the name and score of your last few checked files (up to 12), so you can revisit a past result.
- Popup preferences — how many checks you've run and, if you've unlocked it, when the occasional support popup should stay hidden until.
- Install banner status — whether you've dismissed or acted on the "install as an app" banner, so it doesn't keep reappearing.
Anonymous analytics
We use GoatCounter, a privacy-friendly analytics service, to understand overall traffic to this page — for example, roughly how many people visit and which pages are popular. GoatCounter is designed not to use cookies and not to track individual visitors across different websites, and it does not receive or process the HTML file you check. For full details on how GoatCounter itself handles data, see GoatCounter's own privacy policy.
Links to other sites
SEOCHECKER links to a small number of other sites — for example the SYNTHLUCIDA homepage, WEBZENith, Relax Player, and a Gumroad support page. Clicking one of these takes you to an external, independently operated site with its own privacy practices, which we don't control.
No accounts, no ads, nothing sold
SEOCHECKER doesn't require an account or any sign-up, doesn't show third-party ads, and doesn't sell or share your information — mainly because it doesn't collect any personal information to begin with.
Children's privacy
SEOCHECKER is a general-audience web development tool and isn't directed at children. We don't knowingly collect personal information from children.
Changes to this policy
If how SEOCHECKER handles data ever changes, we'll update this page and the "Last updated" date above.
Questions
If you have questions about this policy, you can reach out via synthlucida.com.
This page is a plain-language description of how the tool actually works, not a substitute for formal legal advice. If you need a legally reviewed policy for your own use of this tool or a similar one, we'd recommend having it checked by a qualified professional.