Client-Side Privacy Guarantee

Subtitle content is parsed and repaired entirely in your browser using Web Workers. Your scripts and dialogue never touch a remote server.

Your Subtitles Never Leave Your Device.

Effective Date: September 29, 2026
Contact: contact@subpreflight.pro

SubPreflight was built from day one on a zero-upload principle. We believe subtitle diagnostics and repairs should never require surrendering your intellectual property, confidential video scripts, or client dialogue to remote cloud servers.

1. The Technical Architecture

Most web utilities upload your file to a server, execute a script in Python or Node.js, and return a download link. SubPreflight works completely differently:

Your Subtitle File (.srt / .vtt)
               ↓ [Read via Browser FileReader API]
        Client-Side Web Worker (in your Browser memory)
               ↓ [Instant Parse, Validate & Repair]
        Exported Clean Subtitle File (Downloaded directly)

All string parsing, regex evaluation, timestamp calculation, and file conversions occur directly inside your browser's V8 or JavaScriptCore engine.

2. What We Never Collect

No Subtitle Content: We never transmit or store dialogue text, cue settings, or timestamps.
No Script or Video Audio: No media is ever requested or ingested.
No Filenames Containing Dialogue: Analytics never capture file text or user transcript data.

3. What We Store Locally

SubPreflight requires no user accounts. Your theme preference (dark or light mode) is saved in your browser's localStorage. It never leaves your device and is never transmitted to us or any third party.

4. Advertising & Third-Party Cookies

To keep SubPreflight free and maintain zero-upload client-side processing, we work with third-party advertising partners, including Google AdSense.

Third-Party Vendor Cookies: Third-party vendors, including Google, use cookies to serve ads based on a user's prior visits to this website or other websites on the internet.
Personalized Advertising: Google's use of advertising cookies enables it and its partners to serve ads to users based on their visits to SubPreflight and other sites across the internet.
User Opt-Out: Users may opt out of personalized advertising by visiting Google Ads Settings. Alternatively, users can opt out of a third-party vendor's use of cookies for personalized advertising by visiting aboutads.info.
Absolute Data Isolation: Third-party advertising scripts and cookies never have access to your subtitle files, timestamps, or transcripts. All subtitle files remain isolated in client-side Web Worker memory on your local machine.

5. How to Verify This Yourself

You do not have to take our word for any of the above. Open your browser's developer tools (F12, or Cmd+Option+I on macOS), switch to the Network tab, and load any tool page. Every request in that list will point at subpreflight.pro.

Then drop an .srt or .vtt file onto the page and keep watching the same tab: you will see no outbound POST or PUT request carrying your file, no beacon, and no image pixel fired on your behalf.