[Feedback] VoxSub – a Firefox add-on for dual subtitles, AI translation, and subtitle control

Add-ons Development
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1

Hi everyone,

I’m building a Firefox add-on called VoxSub. The main problem I’m trying to solve is that many online video players only provide one subtitle track, or the available subtitle is not in the language or style the viewer needs.

Add-on link:

VoxSub lets users take an existing subtitle track and create a second translated subtitle track in 20+ languages. It also supports custom instructions during translation, such as simplifying subtitles, rewriting them in a more casual or formal tone, or adapting the wording to a supported dialect.

The add-on also includes dual subtitles, SRT upload, subtitle timing sync, subtitle search, and subtitle appearance customization.

I’m looking for honest feedback from Firefox add-on developers and users, especially on:

  • Is the main use case clear?

  • Does the translation and custom-instruction workflow make sense?

  • Are there any concerns around permissions, privacy, or external translation/AI services?

  • Is this useful for language learners, online courses, anime, or foreign videos?

  • Any suggestions for improving the UX or technical approach?

I’m not asking for ratings or promotion — just honest feedback and criticism.

2

My first suggestion would be: Include a link to the extension :slightly_smiling_face:
(You didn’t use AI to generate your post, did you?)

3

Good point :grinning_face_with_smiling_eyes:

Here’s the link:

And no, I wrote the post myself. I just wanted to explain the idea clearly and get some honest feedback.

If you try it out, let me know what you think.

4

UX: it wasn’t obvious that it’s necessary to click the icon for the extension, for the extension to perform detection.

(I imagined its icon appearing automatically within the YouTube player.)

5

https://sh.reddit.com/r/freebsd/new/?feedViewType=compactView (new Reddit, logged in) with the extension enabled:

image
image1189×948 133 KB

After disabling the extension and then reloading the page:

image
image1189×948 202 KB

Reproducible with a clean profile, without logging in. Almost immediately after enabling the extension, page content disappears.

Firefox 151.0.4 (64-bit), Snap for Unbutu (on Kubuntu 26.04).

6

Thank you for trying VoxSub and for this valuable feedback!

You’re absolutely right about the UX issue. I’m currently working on making the extension icon appear automatically inside the video player when subtitles are detected, without needing to click the toolbar icon first.

Your feedback confirmed that this is the right direction. I’ll update the thread once this improvement is released!

7

Thank you so much for reporting this and for taking the time to test VoxSub so thoroughly!

This is a real bug and I take it very seriously. The extension should never affect pages that don’t have video content — I will fix this immediately.

I truly appreciate your effort in providing screenshots and reproduction steps, it helps a lot!