How we handle your files

Check it yourself in about a minute

You do not need to take our word for it. Your browser can show you exactly what leaves your device:

1. Open your browser’s developer tools — press F12, or right-click the page and choose Inspect.
2. Select the Network tab. This lists every request the page makes.
3. Drop in a subtitle file and run a conversion, then download the result.

Watch the list as you do it. No request carries your file. The subtitle is read with the browser’s built-in file reader, processed in JavaScript on this page, and the download is generated in memory — none of that touches the network.

To be completely straight about what you will see in that tab: the page’s own stylesheet and scripts load when you first open it, and two third-party things load alongside the page — one Google ad and a small, cookieless analytics beacon. Those are part of the page, not your file. You can confirm it by reading any of them: none contains your subtitle text. Better still, do the next test.

Private by architecture, not by promise

A privacy promise is only as good as the code behind it. SyncMySubs is a set of static files served from a content delivery network. There is no application server, no upload endpoint, and no database — nothing on our side is built to receive a file. So it is not that we choose not to look at your subtitles; there is nowhere for them to go and nothing that could read them, even if we wanted to. Many “online converters” work the opposite way: they send your file to a server, convert it there, and send it back. This one does the whole job in the page.

It works offline — and that is the proof

Here is the test that settles it. Load any tool once, then turn off Wi-Fi or pull your network cable, and convert a file. It still works. A tool that quietly uploaded your file could not do that — it would need the connection you just removed. Because everything needed to do the work is already running on your device, it does not. (After your first visit a small service worker keeps the pages cached, so they open offline too.)

Analytics and ads, precisely

Being verifiable means being exact about the parts that do use the network, so here they are in full:

• Analytics: we use Cloudflare Web Analytics, a cookieless, privacy-first tool that gives us aggregate visitor and pageview counts. It sets no cookies, uses no device storage, and does not track you across other sites. It never sees your file.
• Advertising: one ad is shown below each tool, served by Google AdSense, and it loads only once you scroll near it. Like ads across the web, Google may use cookies to serve it. It never receives your file. Full detail, including how to opt out of personalised ads, is on the privacy policy.

Faithful conversions, honestly

We will not tell you a conversion is “lossless” when it cannot be. Formats differ in what they can hold, so some detail genuinely cannot survive a change — and pretending otherwise would just hand you a broken file. Instead each tool keeps everything the target format supports and tells you plainly what it cannot keep. Converting a styled ASS file to SRT, for example, preserves the text and the timing but drops styling and positioning, because SRT has no way to store them; the tool says so before you download, rather than silently discarding it. Faithful and transparent beats a false promise.

Questions about any of this? Reach out through our Ko-fi page, or read the full privacy policy.