A public website.
Your own private garage.
Here’s how this early-access version handles the information you enter.
Your sign-in
Underhood supports ChatGPT sign-in and, when enabled, email/password and Google accounts through Google Firebase Authentication. ChatGPT provides an account identifier, email address, and optional display name. Email signup sends your name, email, and password securely to Firebase through Underhood; Underhood does not save your password in its database or logs. Firebase manages password storage, email verification, and password-reset messages. Email access requires verification. A secure, HttpOnly cookie keeps your sign-in token; Firebase sessions expire after one hour. Google sign-in uses Google’s account chooser and shares your account identifier, email, and display name with Firebase and Underhood. The Firebase browser session is kept in memory and cleared after sign-in; Underhood does not store browser refresh tokens. Firebase may recognize Google and email/password as the same Firebase account under its account-linking rules. A ChatGPT login is connected only when you explicitly prove access to both accounts. Matching email addresses alone never combines garages. Underhood never asks for your ChatGPT password.
What is stored
The app saves the vehicle details, VIN if entered, mileage, service and repair history, fuel purchases, gallons, station names, running expenses, payment dates, cost breakdowns, notes, reminder intervals, shop follow-ups, warranty providers, contract numbers, coverage notes and dates, and document information you provide. Uploaded receipts, photos, and manuals are stored separately from their descriptions. Household sharing also stores membership identifiers, member and invitation email addresses, invitation expiry dates, hashed invitation tokens, and your selected garage. Receipt and manual-page scanning runs on your device using scanner files hosted with this app; documents are not sent to a third-party AI service. Structured records use Cloudflare D1 and uploaded files use Cloudflare R2 through the Sites hosting platform.
Account administration and terms
Underhood stores account identifiers, name and email when provided, observed login methods, account and garage access status, recorded signup dates, and recent app activity. Existing historical dates that were never collected remain unknown. App activity timestamps are updated at most every 15 minutes to measure active use. Complimentary access stores the selected plan, grant date, operator note, and conversion-trial dates when applicable. Complimentary invitations store the invited email, a hash of the private token, expiration, and acceptance status. The operator can review these grants and invitations. We also store the Terms of Service version, acceptance time, login method, and acceptance method. We do not collect a separate IP address or device fingerprint for terms acceptance.
The owner-only admin dashboard shows account and aggregate usage information, including counts of vehicles, RVs, services, fuel purchases, files, and stored file sizes. It does not provide a customer-receipt viewer or browse individual service notes. Authorized administration can suspend users or garages and permanently remove app data. Reasons and actions are kept in an administrative audit log. Help & account requests save the text you submit for the owner to review; avoid including sensitive documents or passwords.
Permanent account deletion removes active garage records and uploaded files, household memberships, notification preferences, and account-request messages. Limited identity mappings and access-blocking identifiers prevent a deleted account from reopening through a connected login. Terms acceptance, necessary billing references, and audit records may be retained for security, consent, and legal purposes. Deleting an Underhood account does not delete an external Google, Firebase Authentication, or ChatGPT identity. We do not silently reactivate a suspended or deleted account when it signs in again.
Vehicle autofill
Choosing Fill details from VIN sends that VIN to the US National Highway Traffic Safety Administration (NHTSA) through Underhood to retrieve available vehicle identification details. Entering a year and make requests matching models from NHTSA. These lookups do not send your name, email, receipts, or service history. Suggestions for services, shops, stations, and suppliers come from records in your currently selected garage and common service names. Lookup results stay in the form until you save the vehicle.
Optional email and schedule services
Email preferences are stored per person and garage, including the signed-in email address, opt-in choices, and snooze date. Email delivery is currently awaiting connection. Once enabled, opted-in garage reminders and summaries are sent through Resend; that provider receives your email address and message contents, including vehicle names and due work. Delivery attempts keep a copy of the message to avoid duplicate sends. You can turn emails off in Account or through an unsubscribe link. Removing household access stops future reminder access to that garage.
VIN schedule lookup is awaiting a vehicle-data connection. When you choose to use it after connection, the vehicle VIN is sent to Vehicle Databases. Returned mileage schedules and vehicle identity are cached for up to 30 days between lookups. Daily lookup usage counters are kept separately from vehicles to enforce the request limit, including after a vehicle is removed. Neither this lookup nor email delivery sends your receipt files to those providers.
Who can view your garage
The home and help pages are public. Garage records, reports, and document downloads require sign-in and are checked against the current owner’s account. Other users can access your garage only if you explicitly invite them to your household. Accepted members can view and edit garage records and download files. You can remove their access in Account. An invitation is tied to the recipient’s sign-in email and expires after seven days. This is access-controlled storage, not end-to-end encryption; site operators and hosting providers may have administrative access needed to operate the service.
Your exports and deletions
Use Reports to download a vehicle report, running-cost summary, costs CSV, or service-history CSV. Account offers a JSON export of all your structured garage data and a list of your documents. You can download original files separately or together with a vehicle report in a ZIP. Calendar exports contain vehicle names, service titles, dates, and notes; your calendar provider handles the file after you import it. You can remove individual entries or vehicles, or permanently clear your garage in Account. Clearing your garage removes the app’s active records and uploaded files. Hosting-provider backups and operational logs may follow their own retention periods.
Removing a service, fuel purchase, or running expense keeps its receipts in the vehicle’s Files area. Removing a vehicle or clearing the whole garage also removes its receipts. Files and reports you already downloaded remain on your device.
Payments and tracking
Payments are paused. Underhood does not collect card details or bill you. Invitation links are private; share them only with the intended household member. The app stores a hash of each invitation token. This app does not add advertising trackers or a separate marketing analytics service. To limit abusive sign-in attempts, Underhood temporarily stores counters keyed by hashed email addresses and network addresses. The hosting and sign-in providers may use their own cookies and operational logs to run their services.
Keeping useful records
Only upload documents you want stored with your vehicle. You can leave your VIN blank and cover unnecessary personal details on a receipt before uploading it. Review exported reports before sharing them, and keep original copies of paperwork you need.