Free Online Media Tools

Subtitle format converters

Jump to a single-purpose converter for the most common subtitle pairs. Each runs locally in your browser with the same no-upload privacy guarantee.

Why these tools run in your browser instead of a server

Almost every online media tool works the same way: you upload a file, a server processes it, and you download the result. That model is simple to build, but it carries real costs. Your file passes through infrastructure you do not control, you wait for an upload and a download that are often slower than the work itself, and the operator has to pay for that bandwidth — which is exactly why those services end up with file size caps, queues, registration walls, watermarks or advertising.

Running the same work inside your browser removes all of it. Modern browsers can decode video and parse text at close to native speed through WebAssembly, so repackaging an MKV or converting an SRT happens on your own CPU. There is nothing to upload, nothing for us to store, and no reason to impose an arbitrary size limit. It also means the tools keep working after the page has loaded, even if your connection drops.

Who these tools are for

You were sent a file you cannot play

Someone emails you an .mkv or an .avi and QuickTime refuses to open it. Rather than installing a player or hunting for a converter, drop the file into the browser player and watch it straight away.

You work on a machine you cannot install software on

Work laptops, shared computers and locked-down environments frequently block installation. A browser tool needs no administrator rights and leaves nothing behind.

You handle material you would rather not upload

Unreleased footage, client drafts and confidential transcripts are poor candidates for a third-party server. Because processing is local, nothing leaves the machine.

You move subtitles between formats regularly

Subtitle files arrive in whatever format the source happened to use. Converting between SRT, VTT, ASS, SBV and TXT is a routine step in most caption and localisation workflows.

Privacy: what actually happens to your files

Both tools are implemented with JavaScript and WebAssembly that run on your device. When you open a file, the browser reads it from disk into memory; everything after that — parsing, repackaging, re-encoding, conversion — happens inside that browser tab. No request carrying your file content is ever sent to our server, and there is no copy for us to delete afterwards.

The only network traffic is the page itself, plus a one-time download of the FFmpeg WebAssembly engine (about 30 MB) the first time the video player needs to convert a file. That engine is cached by your browser afterwards. If you want to verify any of this, open your browser's network tab while using a tool — you will see no upload of your media.

How the online tools compare to desktop software

Browser tools and desktop software solve the same problem under very different constraints, and it is worth being honest about where each one wins.

A browser tool wins on convenience: nothing to install, no administrator rights, no licence, and it works on any operating system including machines you do not own. It also wins on privacy, because the file never leaves your device. That makes it the right choice for a one-off job — previewing a file someone sent you, converting a single subtitle, or working on a locked-down computer.

Desktop software wins on speed and capability. It can use hardware decoding and full multi-core CPU encoding rather than a single browser tab, it is not constrained by the roughly 4 GB memory limit a tab operates under, and it handles things a browser cannot: Blu-ray discs, playlists, embedded subtitle tracks, multiple audio tracks and instant seeking through a two-hour 4K file. If you work with video regularly rather than occasionally, desktop software is the better tool — which is why these pages point towards Total Video Player Pro for Mac for that kind of work.

Common scenarios for these browser tools

Preview a draft before sharing it

A client sends a rough cut in MKV or a subtitle draft in ASS. Instead of installing software just to check it, open the file in the browser player or convert the subtitle to SRT in a few seconds. You confirm the content is right before you commit to a heavier workflow.

Work on a computer you do not own

Hotel business centers, university labs and borrowed laptops often prevent software installation. A browser tool gives you a fully functional video preview and subtitle converter with no administrator rights and no leftover files.

Fix a single subtitle quickly

YouTube downloaders produce SBV, old DVDs produce SUB, editors export VTT, and translators send SRT. Converting one file, shifting its timing by half a second, and cleaning up the encoding is faster in a dedicated converter than opening a full subtitle editor.

Tips for getting the best results

For the video player

Start with a smaller file if you have never used it before, so you can see how quickly your machine handles conversion. Close other memory-hungry tabs before converting a large video. When a file needs re-encoding rather than simple repackaging, expect it to take a noticeable fraction of the video's own duration on a laptop — that is your CPU doing the work locally rather than a server doing it remotely.

For the subtitle converter

Check the detected encoding badge before converting. If it shows anything other than UTF-8, the original was saved in a legacy encoding and the tool is quietly correcting it for you. Use the Time shift field to fix sync at the same time as converting, so you only download one corrected file. Keep the original subtitle until you have played the converted version all the way through.

Frequently asked questions