Privacy Policy

This website

This website presents HeyFit. It has no customer area: “Log in” leads to the Heylio suite's shared login (app.heylio.io), which has its own privacy policy.

• Contact: this website no longer has a contact form (removed on October 13, 2026). If you write to us by email, or if you used the former form, your message and the contact details that come with it are kept for three (3) years from the last contact, then deleted. Legal basis: legitimate interest (answering your request).
• Hosting: as for any website, the host processes the technical connection data (IP address, browser, requested page) needed to display the pages and protect them.
• No cookies: no cookies, no audience measurement and no advertising on this website; fonts are served by the website itself. See the cookie policy.

The website's processor:

• Vercel Inc. — website hosting (United States; European Commission standard contractual clauses).

To exercise your rights over this data: rgpd@fastoche.tech.

At a glance

• HeyFit collects no personal data about your store’s customers: no name, email, address, order, or body measurements stored on our servers. The measurements entered are only used to compute the advice, without being stored; if the customer asks for it (box unticked by default), a copy is kept in their own browser, and that copy never leaves it.
• HeyFit keeps your store’s data (identity, Shopify connection, size charts), the accounts of your team members who use the admin, and the team list of your Heylio account (members and invitations) that Heylio sends it.
• No advertising, no audience-measurement tools, no selling or sharing of data for commercial purposes.
• On uninstall, access to your store is cut immediately; 48 hours later, all of the store’s data is deleted.

Who is responsible for your data

HeyFit is published by FASTOCHE, a French simplified joint-stock company (SAS) with a share capital of €3,000, registered with the Aix-en-Provence Trade and Companies Register under number 922 556 212 (SIRET 922 556 212 00020), with its registered office at 1004 route de Coudoux, 13122 Ventabren, France. FASTOCHE also publishes HeyReturn, part of the same Heylio suite.

FASTOCHE is the data controller for the data described below. Contact: hello@heylio.io. Data protection officer: rgpd@fastoche.tech, or by mail: DPO — FASTOCHE, 1004 route de Coudoux, 13122 Ventabren, France.

Store data

When a merchant installs HeyFit, we keep:

• the store’s identity: name, myshopify.com domain, public domain, currency, time zone, and the Heylio account it belongs to (or, until a Heylio account claims it, a provisional account specific to the store, created the first time HeyFit is opened in the Shopify admin);
• the Shopify access token, limited to reading the catalog (read_products scope), and its refresh token (the access token expires after one hour and is renewed automatically). They are stored server-side only, in a table read solely by internal functions; they are never sent to the browser and are only sent to Shopify, over HTTPS. They are erased as soon as the app is uninstalled;
• the size charts created by the merchant (name, category, unit, measurements per size) and their assignments (product, collection, product type, or default chart);
• the change history of each chart: for each of the last 50 changes, the chart’s content and assignments, the type of change, the date and its author (see “Admin user accounts”);
• the merchant’s statements about a product (“runs small”, “runs large”, “true to size”).

The catalog is read on demand from Shopify, to check that a chart matches the products’ sizes: it is not copied into HeyFit. One exception: when you look for products without a size chart, HeyFit keeps the list of those products (ID, title, image, collections, type) for 7 days at most, then erases it; it contains no customer data.

Store customers: no personal data

On the product page, the “Find my size” button lets a customer enter body measurements (chest, waist, hips, inseam) and a fit preference. These values are used to compute the recommended size, then discarded by our servers: they are never stored there. If they don’t know their measurements, the customer can instead enter their height, weight, age and body type (female, male or not specified): this information is used to estimate their measurements IN their browser, from public anthropometric reference data; it is never sent to our servers, which only receive the estimated measurements and the fact that they are estimated. No cookie is set. In the customer’s browser, local storage (localStorage, on the store’s domain) keeps: the display unit they chose (centimeters or inches), always; their measurements (in centimeters) or, if they asked for an estimate, their height, weight, age and body type, along with their fit preference and the date, only if they tick the “Remember my measurements on this device” box (for an estimate: “Remember my height, weight, age and body type on this device”), unticked by default, so they can be offered again on the store’s other products; this choice is remembered for the next products. With the box unticked, nothing is kept; if they untick it, whatever was kept is deleted at once. This copy never leaves their device: it is never sent to our servers, and HeyFit cannot read it (only the measurements entered for the product shown are sent, to compute the advice, as described above). The customer can delete them at any time with “Clear my measurements” — “Clear my details” for an estimate — (or by clearing their browser data), and they are deleted automatically after one year.

To measure the guide’s effect, HeyFit records each displayed recommendation in anonymous form: the store, the product, the chart, the recommended size, the confidence score, the fit preference, the NAMES of the measurements provided (never their values), whether they were estimated and the date. No customer identifier (the one Shopify adds to the request is ignored), no IP address, no session: a recommendation cannot be linked to anyone. Likewise, after a recommendation, HeyFit anonymously records the size the customer settles on (the one added to cart, otherwise the last one selected on the product page before leaving it): the recommended size, the chosen size, whether it is larger or smaller, the product, the chart, where the choice came from, whether the “Select size …” button was used and the date, to measure whether the advice is followed — with no link to the customer or to the recommendation before it. These recommendations are also added up per day and per product (numbers only) for the merchant’s Statistics screen. To slow down a visitor who would repeat the request in a loop, HeyFit also counts, minute by minute, each visitor’s requests: the visitor is only identified there by a one-way fingerprint (HMAC) of their IP address (never the address itself), specific to the store and deleted after one hour.

Storefront requests go through Shopify’s app proxy, which signs them; HeyFit verifies that signature.

Size returns received from HeyReturn

If the store also uses HeyReturn, it sends HeyFit the items returned for a size reason, so the recommendation can be adjusted. For each return, HeyFit keeps only: an opaque identifier of the return at HeyReturn (so it is never counted twice), the product and its name, the variant, the returned size and the wanted size, the reason label (“Too small”), the direction of the return and the dates.

No customer data is received or kept: no name, email, address, order number, or free-text comment. Any other field sent is ignored. HeyFit derives per-product counters from these returns. The history of a store that used HeyReturn before installing HeyFit may be prepared in advance, with these fields only and its size charts, then attached to the store when it installs HeyFit; it is deleted on request or with the store.

Admin user accounts

HeyFit manages no passwords. On app.heyfit.app, access to the admin goes through the shared Heylio sign-in. At each sign-in, Heylio sends, signed, the person’s name, email address, role (Owner, Administrator or Agent), Heylio identifier, suite account and list of stores (name and domain). HeyFit keeps them with the open session to control access: each user only sees the stores of their account. If the person chooses the interface language, HeyFit keeps that choice on their user and sends it to Heylio, so that it applies across the suite.

Heylio also sends HeyFit, signed, the team list of the suite account, at each change and once a day: the account name and, for each member, their name, email address, whether that address is verified, their role and whether they are the owner; for each pending invitation, the invited email address, the planned role and the expiry date. These people have not necessarily opened HeyFit. This list is used to show the team in Settings → Team, to apply a role change right away and to sign out a person removed from the account. Each submission replaces the previous one: only the latest list is kept, with a log of submissions (version number, date and number of removals and role changes, with no name or address). While the account has no store in HeyFit, only the version number is kept; the list and its log are deleted with the account’s last store (see “Deletion”). A person coming from the Shopify admin, without a Heylio account, is not in it.

When a user creates, edits, imports, assigns, unassigns or restores a size chart, HeyFit copies their name and email address (as sent by Heylio) into the chart’s history, with the date of the change, so the store’s team knows who did what. A person coming from the Shopify admin appears there without a name or email address. This history is visible only to the store’s users.

HeyFit also opens directly inside the Shopify admin, without a Heylio account. Shopify then sends a signed identity token, valid for one minute, which HeyFit verifies. HeyFit only keeps the person’s Shopify user identifier (a number, with no name or email address), linked to the store, with the Administrator role and the open session: this person only sees that store. The identity token itself is neither stored nor logged.

In the browser, on app.heyfit.app, the admin only uses technical storage, with no cookie: in local storage (localStorage), the session token and its refresh token, the chosen theme (light, dark or the device’s), the chosen language, whether the menu bar is expanded or collapsed and whether the “Install HeyFit” card is hidden and, for two minutes, the time of a sign-out (to close the session in every tab); in the tab’s storage (sessionStorage, cleared when it closes), the page to return to after sign-in, the time of the last trip through the Heylio sign-in (to avoid a loop), the time of the last reload after a HeyFit update (to avoid a loop) and, during an installation, the store’s attach token. Inside the Shopify admin, nothing is written to the browser: the session token, theme and language stay in memory and disappear when the page is closed. No advertising or analytics cookies.

Technical error log

To detect and fix outages, HeyFit keeps a log of technical errors from the admin, the server and the storefront button. For each error: its technical message and the start of its trace in the code, the screen concerned without its parameters (“/grilles/:id”), the HeyFit version, the browser family and major version (“Chrome 129”), the number of occurrences and the dates of the first and last occurrence. On the storefront, only a predefined error code is sent, without any text from the page.

This log contains no personal data: no name, email address, IP address, or user, customer or store identifier. Email addresses, tokens, long digit sequences and URL parameters an error might quote are masked before anything is stored. It is kept at Convex, with no third-party error-tracking tool.

Importing a size chart with AI

When a store administrator imports a size chart with AI, HeyFit sends OpenRouter, once, the content the merchant chose: the screenshot of the chart, the text of a public web page whose address they gave, or the title and description of a product read from Shopify. None of the store’s customers’ data is sent, nor the user’s name or email address.

OpenRouter passes this content to the Claude AI model, designed by Anthropic, and has it read only by a host of that model that keeps nothing (zero data retention) and does not use the data to train models; hosting in the European Union is requested first. OpenRouter only keeps technical data about the request (number of words read and written, duration, cost), not the content.

HeyFit keeps neither this content nor the AI’s answer: the proposed chart comes back to the screen and is only saved if the merchant creates it. Only a count of imports per store and per day is kept, for the daily limit; it is deleted with the store.

Why, and on what legal basis

• Providing the service to the merchant (charts, recommendation, learning from returns): performance of the contract.
• Controlling access and securing the service: legitimate interest.
• Anonymously measuring the size guide’s effect: legitimate interest, with no personal data.
• Detecting and fixing technical errors: legitimate interest, with no personal data.
• Answering privacy requests sent by Shopify: legal obligation.

Hosting providers and processors

• Convex, Inc. — database and service execution; data hosted in the European Union (Ireland, eu-west-1 region).
• Vercel Inc. — hosting of the app.heyfit.app web interface and its fonts (no font is loaded from a third party).
• Shopify — the store’s platform: installation, access token, opening HeyFit inside the Shopify admin (user identity), storefront app proxy, privacy requests.
• Heylio — shared sign-in of the suite (users’ identity and role, the account’s team list).
• OpenRouter, Inc. — AI reading of a size chart the merchant imports (merchant content only: screenshot, public web page or product description; no customer data), not kept by HeyFit; a US company that passes the content to Anthropic’s Claude model at a zero-data-retention host (Anthropic or a host of its models, such as Google Cloud), with no training on this content.

These providers only use the data to deliver their service. Any transfer outside the European Union is governed by the European Commission’s standard contractual clauses. HeyFit never sells or rents any data.

Retention

• Store data, charts, anonymous recommendations and size returns: as long as the app is installed.
• Shopify access token and refresh token: erased as soon as the app is uninstalled.
• All store data: erased on receipt of the shop/redact request Shopify sends 48 hours after uninstall (unless the store has reinstalled HeyFit in the meantime).
• Size chart history (with the name and email address of the author of each change): the last 50 changes to each chart, older ones being deleted automatically; deleted with the chart, and with all the store’s data.
• Team list received from Heylio: replaced at each submission (at least once a day); reduced to its version number while the account has no store in HeyFit; deleted, with its log, when the account’s last store is deleted (shop/redact), or on request.
• User accounts: as long as the Heylio account, or for access from the Shopify admin the store, grants access to HeyFit; deleted on request.
• Technical sign-in and installation tokens: purged automatically after they expire (one hour at most).
• Technical error log: each error is deleted automatically 30 days after its last occurrence.
• Log of privacy requests received from Shopify (topic, store and, for a customer request, the email address and order numbers concerned as sent by Shopify): kept for 3 years as proof that the request was handled, then the email address and order numbers are deleted automatically; only a record that a request was handled remains, with no customer identifier.

Deletion and requests sent by Shopify

• Uninstall (app/uninstalled): the connection is closed and the access and refresh tokens erased immediately.
• Store deletion (shop/redact): the store, its connection, its charts with their assignments and history, displayed recommendations, the size choices that follow them and their statistics, size returns, counters and statements, the catalog analysis, the known subscription, the onboarding state, the accounts and sessions of people who signed in from the Shopify admin, and the HeyReturn history deposited for this domain (even if the store never opened HeyFit) are erased; if it was the Heylio account’s last store in HeyFit, the account’s team list and its log are erased too. Only the request log remains (see “Retention”) and, so that a reinstall does not reopen a full free trial, a hashed fingerprint of the store’s domain (never the domain itself) with the end date of its trial.
• Customer access or erasure request (customers/data_request, customers/redact): HeyFit holds no customer data; the request is logged and closed automatically, with nothing to provide or erase.

All these requests are authenticated by Shopify’s signature and handled automatically on receipt.

Your rights

Under the GDPR, you have the right to access, rectify, erase, restrict, object to the processing of, and port your data. Write to rgpd@fastoche.tech: we reply within one month.

Store customer: HeyFit holds no data that identifies you. For your order data, contact the merchant you bought from.

You may also lodge a complaint with the French data protection authority, the CNIL (www.cnil.fr).

Security

• Traffic encrypted in transit (HTTPS); Shopify signatures verified on installation, opening in the admin, webhooks and storefront requests; dedicated key for HeyReturn submissions.
• Access isolated per suite account; the Agent role is read-only.
• No secrets in the code: keys live in the server’s environment variables.

Contact and changes

For any question about this policy: hello@heylio.io, or the data protection officer: rgpd@fastoche.tech.

If HeyFit starts processing other data, this page will be updated beforehand, and its date will change.