Privacy policy

Last updated: September 30, 2026

STL Ruler is built to know as little about you as possible. Your 3D files stay on your device unless you save a composition to your cloud storage (Pro). We don't show ads, we don't sell or share your data for marketing, and we don't use tracking cookies.

STL Ruler is run by Chris Arock. Questions or requests: the Support page, or support@stlruler.com.

What stays on your device

Your workspace — models' layout and settings, rulers, text, undo history — is saved in your browser's storage, and the STL files you open are kept in its local database so the workspace comes back after a reload. None of it is sent to us unless you save a composition (see Saved work below). Files no workspace has used for 14 days are removed; Start over or clearing your browser's site data removes everything.

What we store

• Account: display name, email address and your password (stored only as a secure hash), and when you last signed in.
• Subscription: your plan, its price and any promotion it is locked to, its start / renewal / end dates, the customer and subscription IDs from Square, and a record of each payment (amount, plan, date). We never see or store card numbers — card details go straight into Square's hosted fields.
• Saved work: compositions you save — the layout and settings, a small preview image and the STL files their models use, kept in a private storage folder for your account (each file once) — and style presets you save.
• Emails: a log of the service emails we send (to which address, which email, whether it was delivered).
• Security: short-lived counters of sign-up, sign-in, password-reset, checkout, support and export attempts (by IP address, email or account) to stop abuse, and password-reset links, stored hashed and valid for one hour.

What we do not store

• Your STL files, unless you save a composition.
• The drawings of your Pro exports — processed in memory and discarded.
• Card numbers or full card details.
• Any tracking or analytics identifiers.

Support messages

When you write to us from the Support page, your name, email address, topic and message are emailed to our support inbox (through our email provider) so we can answer you — with your plan and account number when you are signed in. They are not stored in STL Ruler's database; we keep them in our mailbox only as long as needed to help you.

How we use it

To provide the service: your account and saved work, billing, and service emails — welcome, password reset, receipts, a renewal reminder before each renewal (3 days before a monthly one, 15 days before a yearly one), payment problems, cancellation confirmations and warnings before saved compositions are deleted. We don't send newsletters and don't use your data for advertising.

Cookies

One essential cookie keeps you signed in (up to 30 days). Our network provider may set a strictly necessary security cookie. There are no analytics or advertising cookies.

Who helps us

• Square processes payments; card details go straight from your browser to Square under Square's privacy notice.
• Hosting and network providers (such as Cloudflare) serve and protect the site and process technical data like IP addresses.
• An email delivery provider (Brevo) sends our service emails and support messages.

They only process data to provide their service to us. Your data may be processed in countries other than yours.

How long we keep it

Account data and style presets are kept while your account exists and deleted when it's deleted. Saved compositions and their STL files are deleted when you delete them, 14 days after your Pro plan ends (we email you first), or with your account; an STL file no saved composition uses any more is deleted right away. Payment records are kept as long as accounting and tax rules require, without a link to you once your account is deleted. Email logs are kept, without the link to your account, for delivery troubleshooting.

Your choices and rights

You can delete your account yourself at any time: account menu → Delete my account. To ask for a copy of your data or to correct it, write to us from the Support page or email support@stlruler.com. Depending on where you live (for example under the GDPR, UK GDPR or California law) you may have further rights, including complaining to your data protection authority. We'll never charge you for exercising them.

Security

Encrypted connections (HTTPS), hashed passwords, HttpOnly session cookies and request-forgery protection.

Children

STL Ruler isn't meant for children under 16, and we don't knowingly collect their data.

Changes

We'll post changes here with a new date.