Free SUB to VTT Converter: No Sign-up, Files Never Uploaded
Convert SUB to VTT free, right in your browser. There is no sign-up or login, no watermark, and nothing is uploaded: your subtitle files never leave your device.
Every cue is read with its start and end time, then written again in the VTT layout.
This pair runs on code that is already in the page, so there is no extra engine to download. Frame-based timing uses the frame rate you set.
- Free
- No sign-up
- Never uploaded
- No watermark
Your files are converted on your device and never uploaded.
How to convert
- Add your SUB files by dragging them onto the converter or by using the file picker.
- Check that VTT is the selected target format; it is already chosen on this page.
- Open the options if you want to change frame rate and text encoding, or keep the defaults.
- Press Convert and watch the progress shown for each file.
- Download each result, or take them all together as one ZIP when you converted several files.
Features
- Reads .sub and writes .vtt.
- Free, with no watermark added to the result.
- No sign-up and no login.
- Your files are never uploaded and never leave your device.
- Batch conversion with a ZIP download for several results.
- The input is recognised by its content, not only by its file name.
Supported formats
| Format | Read | Write | Notes |
|---|---|---|---|
| MicroDVD (SUB).sub | Yes | Yes | Frame-based subtitles: timing is given in video frames, not seconds. |
| WebVTT (VTT).vtt | Yes | Yes | The W3C subtitle format used by the HTML video element. |
About the formats
About SUB
Frame-based subtitles: timing is given in video frames, not seconds.
Needs the video’s frame rate to convert correctly.
About VTT
The W3C subtitle format used by the HTML video element.
Supports basic styling and positioning.
SUB vs VTT
SUB does not support transparency, and VTT does not.
MicroDVD (SUB) files use the .sub extension and WebVTT (VTT) files use .vtt, so the converted file gets a new name with the new extension.
Privacy: how it works
- Your SUB files stay on your device. The page reads each file with the browser's file API, converts it with code running in the tab, and hands the result back as a download. No upload happens, so there is no copy of your file on our servers to protect, delete or leak.
- There is nothing to sign up for and no login. The converter does not ask for an email address, and it does not need to know who you are to do its job.
- You can check the claim yourself: open your browser developer tools, watch the Network tab while a file converts, and you will see no request that carries your file.
Tips
- Open the result in your player to check that the timing still lines up.
- Use UTF-8 for text encoding unless an older device needs something else.
- Styling, colours and positions only survive between formats that support them.
- Keep the original file in case you need the styling later.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial, no credit card and no watermark added to your results. Ulkaa Tool does the conversion with your own device, so there is no server bill to pass on to you.
Are my files uploaded?
No. Your SUB files are read and converted inside your browser and are never sent to Ulkaa or to anyone else. The result is created on your device and you save it from there.
Do I need an account?
No. There is no sign-up and no login. Open the page, add your files and convert. An Ulkaa account is not needed for anything on this tool.
Is there a file size limit?
No limit is set by us. The real limit is your device: the conversion uses your own memory and processor, so very large files can be slow, and a very big batch may need to be split into smaller runs.
What is the difference between SUB and VTT?
SUB does not support transparency, and VTT does not. MicroDVD (SUB) files use the .sub extension and WebVTT (VTT) files use .vtt, so the converted file gets a new name with the new extension.
Can I convert many SUB files at once?
Yes. Add as many files as your device can handle. Each one is converted on its own and you can download them one by one or as a single ZIP.
Will anything be lost when I convert SUB to VTT?
The converter keeps the content of the file. Check the result once, since small differences in metadata or colour handling can happen between formats.
Can I convert VTT back to SUB?
Yes. Open the VTT to SUB page and use the same steps. Converting back does not undo any loss from the first conversion.
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