Thornwick Studios Limited · Prosa
Cookie Policy
What Prosa stores in your browser. The application sets the sign-in cookies it needs and a few preferences; it measures use without cookies unless you switch analytics cookies and session recording on. The website loads analytics, and the Meta Pixel for advertising, only after you accept each in the banner.
This Cookie Policy explains what Thornwick Studios Limited ("we", "us" or "our") stores in your browser when you use the Prosa application at write.prosa.so (the "Application") and when you visit the website at prosa.so (the "Website"). Thornwick Studios Limited is a private limited company registered in England and Wales, company number 16682779. Read it with our Privacy Policy, which explains how we use personal data and how to exercise your rights. Questions go to privacy@prosa.so.
1. Cookies and similar technologies
Cookies are small text files that a site places on your device. Browsers also offer other storage, chiefly localStorage and IndexedDB, which a site can use to remember things between visits. This Policy covers all of them. Where we say "cookie" without qualification we mean an actual cookie; where a preference lives in localStorage we say so, because the two behave differently and are cleared differently.
2. The Application
The Application uses what it needs to keep you signed in, a handful of preferences stored on your device, a recovery copy of the manuscripts you open (Section 2.4), and, only if you switch it on, analytics cookies and session recording provided by PostHog. Without that switch, PostHog still counts how the Application is used, but in a cookieless mode that stores nothing on your device and cannot be tied to you; Section 2.3 explains both. It sets no advertising cookies and no third-party cookies. There is no consent banner in the Application; the choice is one question when you first open it and the same switch in Settings afterwards.
2.1 Strictly necessary cookies
Clerk, our authentication provider, sets session and sign-in cookies on write.prosa.so and on its sign-in address, clerk.prosa.so, to verify who you are on each request. One of them, __client_uat, is set on prosa.so itself so that every prosa.so address can tell whether you are signed in; your browser therefore also sends it when you visit the Website, which does not read it. Without these cookies you cannot sign in. They are exempt from consent because they are strictly necessary to provide the service you asked for.
| Cookie | Set by | Purpose | Lifetime |
|---|---|---|---|
Clerk session cookies (for example __session) | Clerk, on write.prosa.so and clerk.prosa.so | Keeps you signed in and lets our servers verify your session | Session, refreshed while you use the Application; cleared on sign-out |
__client_uat, and a copy with a suffix such as __client_uat_dCKOAlYB | Clerk, on prosa.so, so it also reaches the Website | Records when your sign-in last changed (0 when you are signed out), so each prosa.so address can tell whether you are signed in | Up to 400 days; it stays after sign-out, set to 0 |
2.2 Preferences held in localStorage
The Application keeps the following on your device. None of them identifies you to anyone else, none is sent to an analytics service, and all are cleared when you clear site data for write.prosa.so.
| Stored value | Purpose |
|---|---|
| Access unlock | Remembers that this browser has entered the shared access password, when one is in force, so you are not asked again until we rotate it |
| Last opened manuscript, and when | Returns you to the manuscript you were working on |
| Library card style | Your chosen layout for the manuscript library |
| Notifications and "what's new" | Which in-app notices you have already seen |
| Consistency marks | Whether findings are shown as marks in the editor |
| Depth effects | Your choice of visual depth effects |
| Editor theme | Also saved to your account record so it follows you between browsers |
2.3 Analytics: cookieless by default, cookies and recording only if you choose
The Application uses PostHog, our analytics provider, in one of two modes. Which one depends on a single question, asked once when you first open the Application and available afterwards as "Allow analytics cookies and session recordings" under Privacy in Settings.
Cookieless mode (every account). Unless you switch analytics on, PostHog stores nothing on your device: no cookie, no localStorage, nothing to list in this Policy. It counts which screens and features are used, how long things take and where errors occur, against an identifier that PostHog's server derives from your connection and browser signature and replaces every day. The identifier is never linked to your account, so we cannot tell which writer an event came from, and there is no session recording. This runs on our legitimate interest in keeping Prosa working, as the Privacy Policy explains, and does not need consent because it neither stores nor reads anything on your device. No analytics cookie or localStorage entry is set before you answer the question; the cookieless mode runs the same way whatever you answer.
Cookie mode with session recording (only if you switch it on). Turning the switch on is your consent. PostHog then stores an identifier in your browser, links events to your account, and records sessions with every word and every input masked. You can turn it off again at any time in the same place; the Application then stops recording, clears PostHog's identifiers from your browser and drops back to cookieless mode. From that moment nothing new is linked to your account. Session recordings already made are deleted after 30 days; events already collected stay under PostHog's project retention as the Privacy Policy states, and we delete them within 30 days if you ask at privacy@prosa.so.
When the switch is on, PostHog stores the following on write.prosa.so:
| Stored value | Set by | Purpose | Lifetime |
|---|---|---|---|
PostHog identifier and session (cookie and localStorage, names beginning ph_) | PostHog, on our domain | Recognises your browser across visits and groups activity into a session. The identifier is linked to your account so that we can see one writer's journey; it is never shared with anyone else | Cookie up to one year; localStorage until cleared or until you switch analytics off |
What is collected while the switch is on:
- Events: which screens and features you use, clicks on controls, timings, errors, and your browser, device type and screen size.
- Session recordings: a replay of the interface, made from the page structure and your mouse movements and clicks. All text and every input field are masked before the recording leaves your browser, so a recording shows the shape of the screen and never the words of your manuscript, your Story Bible, your Shepherd questions or anything you type. Where you paste or upload text, the content is masked in the same way.
- What is never collected, in either mode: manuscript text, Story Bible content, Shepherd questions and answers, consistency findings, file contents, or anything you type. Automatic capture of clicked text is switched off, and the masking is applied in your browser by configuration, not by later editing.
PostHog stores this data in its European Union region and is a processor acting on our instructions under a data-processing agreement; the Privacy Policy explains where it may be accessed from and on what basis. We do not use analytics or recordings for advertising, and we do not share them.
This Policy is linked from the Policies page in Settings; the switch that controls analytics is under Privacy.
2.4 Recovery copy of your manuscripts, held in IndexedDB
The editor keeps a recovery copy of each manuscript you open in your browser's IndexedDB storage, in a database named prosa-editor-recovery-v1, together with the account it belongs to. It holds the manuscript's text, including changes that have not yet reached our servers, so that nothing you type is lost if the connection drops or the tab closes before a change is saved. It is read only by the editor on that device and is never sent to anyone.
| Stored value | Purpose | Lifetime |
|---|---|---|
Recovery copy (prosa-editor-recovery-v1) | Restores changes that had not reached our servers when you next open the manuscript | Stays after you sign out, because it may hold the only copy of your latest changes. Removed when a different Prosa account signs in on that browser, or when you clear site data for write.prosa.so |
Anyone who can use that browser profile can read it. Write only on devices you trust, and clear site data for write.prosa.so before handing a device to someone else.
3. The Website
3.1 Before you choose
When you first visit prosa.so a banner asks whether you accept analytics and, separately, advertising. "Decline" refuses both, "Analytics only" accepts analytics alone, and "Accept all" accepts both. Until you choose, nothing is loaded and nothing is stored except your eventual choice. If your browser sends the Global Privacy Control signal, we treat that as declining both: no banner is shown and nothing is set. You can still accept analytics later from "Cookie settings" in the footer, but advertising is not offered and the Meta Pixel never loads while your browser sends the signal.
3.2 If you accept analytics
PostHog, our analytics provider, loads and stores a pseudonymous identifier and a session identifier in a first-party cookie and in localStorage on prosa.so. It records page views, referrer, device and browser information, page-performance metrics and a session replay with text inputs masked. On the certificate verification page it also records the outcome of each check, how long it took, the size and fingerprint of the file checked, and the identifiers and claims inside the certificate; never the manuscript itself. PostHog is configured in its European Union region.
| Stored value | Set by | Purpose | Lifetime |
|---|---|---|---|
cookie_consent (localStorage) | Us | Your analytics choice, "yes" or "no" | Until you clear site data or change it |
ad_consent (localStorage) | Us | Your advertising choice, "yes" or "no" | Until you clear site data or change it |
PostHog identifier and session (cookie and localStorage, names beginning ph_) | PostHog, on our domain | Recognises a returning browser and groups a visit into a session | Cookie up to one year; localStorage until cleared |
3.3 If you accept advertising
We advertise Prosa on Facebook and Instagram. If you accept advertising, the Website loads the Meta Pixel, a script from Meta Platforms Ireland Limited ("Meta"), so that we can measure which of our ads lead people to Prosa and Meta can show them to people more likely to be interested. The Pixel sends Meta two things: that you visited, with the page address, the page you came from, your browser and device type and your IP address, when the page loads; and that you clicked a link to sign up for the Application, the first time you do on a page. We have switched off the Pixel's automatic configuration, so it does not send button text, page content or anything typed into a form. It does not run in the Application.
Meta sets the identifiers below on prosa.so. If you are signed in to Facebook or Instagram in the same browser, Meta can also read its own cookies on its domains (for example fr on facebook.com) and link the visit to your Meta account; those cookies belong to Meta and are covered by Meta's Cookie Policy. We collect the information jointly with Meta for our advertising; what Meta does with it after receiving it is governed by Meta's Privacy Policy, as the Privacy Policy explains.
| Stored value | Set by | Purpose | Lifetime |
|---|---|---|---|
_fbp (cookie) | Meta, on our domain | Recognises a returning browser for measuring our ads | 90 days, renewed on each visit |
_fbc (cookie) | Meta, on our domain | Only if you arrived by clicking one of our Meta ads: records that click, so the visit can be credited to the ad | 90 days |
lastExternalReferrer and lastExternalReferrerTime (localStorage) | Meta, on our domain | The last site outside prosa.so you arrived from, and when, so a visit can be credited to the ad that led to it | Until cleared, or until you choose "Analytics only" or "Decline" |
3.4 Changing your mind
"Cookie settings" in the Website footer reopens the banner on every page. Choosing Decline stops PostHog and the Meta Pixel and clears their identifiers on prosa.so; "Analytics only" stops the Meta Pixel and clears its identifiers. Data already collected is handled as described in the Privacy Policy, and you can manage what Meta holds in your Facebook or Instagram settings. Declining does not affect your use of the Website.
4. Third parties
Everything above is set on our own domains. We set no third-party cookies. The one exception is Meta's own cookies on its domains, which Meta may read or set only if you accept advertising on the Website (Section 3.3). Cloudflare, which proxies both domains, may set the two cookies below only where it needs to distinguish automated traffic from people. Both are strictly necessary to serve the page, need no consent, and are not used to identify you to us.
| Cookie | Set by | Purpose | Lifetime |
|---|---|---|---|
__cf_bm | Cloudflare, on prosa.so and write.prosa.so | Bot management: tells automated traffic from people | Up to 30 minutes |
cf_clearance | Cloudflare, on prosa.so and write.prosa.so | Remembers that you passed a Cloudflare challenge page, so you are not challenged again | Up to 30 minutes |
5. Managing cookies in your browser
You can delete or block cookies and site data through your browser's settings. Blocking the Clerk session cookies will prevent you from signing in to the Application. Clearing site data for write.prosa.so will sign you out, reset the preferences in Section 2.2, including the access unlock, remove the recovery copy in Section 2.4, including any changes that had not yet reached our servers, and remove PostHog's identifiers; because your analytics choice is saved to your account, it will still apply when you sign in again unless you change it in Settings.
6. Legal basis
United Kingdom. Under the Privacy and Electronic Communications Regulations 2003, the Clerk session cookies in Section 2.1, the preferences in Section 2.2 and the recovery copy in Section 2.4 are exempt from consent because they are strictly necessary to provide the service you asked for (keeping you signed in, and not losing what you write) or solely serve to remember choices you made. The cookieless mode in Section 2.3 stores nothing on your device and reads nothing from it, so Regulation 6 does not apply to it; it uses only information your browser already sends with each request. Analytics cookies and session recording in the Application (Section 2.3) and analytics and advertising on the Website (Section 3) are set only on your consent: in the Application by answering the question on first use or turning on the switch in Settings, on the Website through the banner, which asks about analytics and advertising separately. We do not rely on the statistical-purposes exemption introduced by the Data (Use and Access) Act 2025, because in cookie mode the data is linked to your account and session recordings go beyond statistics. Consent can be withdrawn at any time, as easily as it was given, and withdrawal does not affect your use of Prosa. To the extent anything stored constitutes personal data, the Privacy Policy sets out your rights under the UK GDPR.
United States. We do not sell personal information. If you accept advertising on the Website, the Meta Pixel shares your visit and your clicks into the Application with Meta, which state privacy laws such as the CCPA treat as sharing for cross-context behavioural advertising; it runs only on that opt-in, and never while your browser sends the Global Privacy Control signal. The Application shares nothing with advertisers. Your rights under applicable state privacy laws, and how to exercise them, are set out in the Privacy Policy.
7. Changes
We may update this Policy when what we store changes. Material changes are announced in the Application or on the Website and recorded in the version history below.
Version history
- 1.1.2, 3 October 2026. The Meta Pixel sends Meta less: only the first click on a link to sign up for the Application on a page, not every click into it.
- 1.1.1, 1 October 2026. Corrected where Clerk's sign-in cookies live: on write.prosa.so and clerk.prosa.so, with
__client_uaton prosa.so itself. That means the Website also receives it, without reading it, and it stays for up to 400 days after sign-out. - 1.1.0, 1 October 2026. The Website's banner asks about advertising separately from analytics. If you accept advertising, the Meta Pixel measures our Facebook and Instagram ads: it records your visit and clicks into the Application, sets
_fbpand_fbcand two localStorage entries, and may let Meta link the visit to your Meta account. It never loads under Global Privacy Control and never runs in the Application. - 1.0.1, 29 September 2026. The editor's recovery copy of your manuscripts, held in IndexedDB, listed with how long it stays and how to remove it.
- 1.0.0, 5 September 2026. First public-release policy. Combined the application and website policies into one. Removed Stripe authorisation cookies and "security" and "framework" cookies. Listed the actual Clerk cookies and localStorage preferences. Application analytics described in two modes: cookieless and anonymous for every account, cookies and masked session recording only for accounts that switch it on.
- 0.2.0, 3 June 2026 (application) and 22 June 2026 (website). Company renamed to Thornwick Studios Limited.
- 0.1.0. Earlier policies under the TrueTale name.