Updated 25 October 2026
Cookies and web storage
The application code sets no cookies. It uses localStorage and sessionStorage for the features listed below. These are browser storage technologies even though they are not cookies. No advertising or analytics storage is included in the application.
Appearance preferences
Changing appearance saves a small preference so the next page uses your chosen system, light or dark mode. It contains no tool input. Clear the site’s stored data in your browser to remove it.
Optional lesson progress
Remembering progress is off until you choose it in a lesson. It stores progress metadata, not selected answers or tool input. Turn the feature off to remove the enabled preference and saved record, or use the learning clear control to remove the progress record.
Optional temporary workspace
The workspace switch enables tab-scoped saving of allowlisted numeric inputs and choices. Turn it off to remove saved workspace settings, or use a tool’s clearing controls to remove that tool’s settings. Free text and results are excluded.
One-time calculator hand-offs
When you explicitly choose to open a related calculator with suggested settings, the application can use a one-time tab record. It expires for use after five minutes and is removed when read. If it is never read, the entry may remain in tab storage until the session ends.
Browser controls
Your browser’s site-data controls can remove all stored settings for this site. Clearing them resets appearance and saved progress. Browser session restoration can preserve tab storage; use browser controls when you need to remove it immediately. Calculations continue when optional storage is unavailable.
Hosting and security storage
Cloudflare provides hosting, content delivery and security. Depending on the security features applied to a request, Cloudflare may use security cookies such as cf_clearance or __cf_bm. These are separate from optional application storage and Google advertising storage. Their purposes and feature-specific lifetimes are described in the linked Cloudflare cookie documentation; this notice does not claim every listed Cloudflare cookie is used on this site. No separate analytics service is enabled.
Further information
The Privacy Policy describes website processing separately from these local browser settings.
Provider privacy information and advertising controls
- Cloudflare privacy policy
- Cloudflare security cookies and their lifetimes
- How Google uses information from sites that use its services
- Make a data protection complaint to the UK ICO
- Cloudflare D1 recovery history and backup retention
- Google personalised advertising settings
- Industry opt-out choices for participating advertising providers
Browser storage reference
| Storage name | Type | Purpose | Retention |
|---|---|---|---|
engineering-toolbox-theme | localStorage | Your selected system, light or dark appearance | Until changed or removed in browser site-data settings. |
engineering-toolbox-learning-enabled | localStorage | Whether you opted to remember lesson progress | Until you disable remembered progress or clear site data. |
engineering-toolbox-learning-v1 | localStorage | Lesson IDs, completion, first-attempt outcomes, attempt counts and update times; no selected answers | Until cleared using lesson controls or browser site-data settings. |
engineering-toolbox-workspace-enabled | sessionStorage | Whether safe-value workspace saving is enabled for this tab | Until disabled or the browser tab session ends. |
engineering-toolbox-workspace-v1 | sessionStorage | Allowlisted numeric inputs and list choices; no free text or results | Until disabled, cleared for the tool, or the browser tab session ends. |
engineering-toolbox-handoff-v1 | sessionStorage | A one-time transfer of selected non-sensitive settings after you choose a linked tool | Usable for five minutes and removed when consumed; an unused entry can remain until the tab session ends. |