Embedded Subtitles, Sidecar SRT Files or Burned-In Text: Where Each Works

The three options at a glance

Sidecar file

A separate text file (SRT, VTT and others) delivered beside the video. The player or platform loads it alongside.

Embedded track

A subtitle stream stored inside the container (MKV, MP4, MOV), selectable in the player's subtitle menu.

Burned-in

Text rendered into the video frames during export. It is part of the picture, not a separate stream.

Sidecar and embedded subtitles are both soft subtitles: the viewer can usually turn them on or off and choose a language. Burned-in subtitles are hard subtitles. The related question of whether captions are open (always visible) or closed (viewer-controlled) is covered in open vs closed captions; this page is about how the text is stored and delivered.

Broadcast television uses yet another approach, with caption data carried inside the video signal itself. That world is described in CEA-608 vs 708.

Sidecar files: where they work

A sidecar file is plain text with timing, which makes it the most portable form. SRT is the most widely accepted; WebVTT is the native format for captions in web browsers.

• Video platforms: most expect captions as an uploaded file, separate from the video. Many accept SRT and VTT; check each platform's current list.
• Websites: the HTML video element loads captions from a VTT file through a track element, and most web players build on that.
• Desktop media players: many automatically load an SRT that sits in the same folder and shares the video's file name, and let you open one manually otherwise.
• Learning platforms and video hosts: commonly take one caption file per language.

The weakness is that a sidecar can get separated from its video. Email the MP4 without the SRT and the subtitles are gone. Native video apps on phones and some TVs also ignore sidecar files. If a file fails to load at all, SRT file not working walks through the usual causes.

Embedded tracks: where they work

An embedded track lives inside the container, so the subtitles travel with the video automatically. How well that works depends on the container and the player.

MKV is the most flexible: it can hold SRT text, styled ASS/SSA subtitles with embedded fonts, and image-based subtitles ripped from discs, in as many languages as you like, each with language tags and default or forced flags. MP4 and MOV support a simpler timed-text format, which Apple devices and some players handle well and others ignore. The container differences are covered in MKV vs MP4.

Embedded tracks suit personal media libraries, files handed to someone who will play them in a capable desktop player, and archives where you want one self-contained file. They suit uploads less well, because many platforms do not read subtitle tracks inside an uploaded video and expect a separate file instead. Browsers generally do not display text tracks embedded in a video file either.

Burned-in subtitles: where they work

Burning in renders the text into every frame. The result shows in every player, on every platform, in every feed, with no menu or setting involved. That is why burned-in captions are common on short social videos, which are often watched on mute, and on screener copies sent for review.

The cost is permanence. Burned-in text cannot be switched off, translated, corrected, resized or restyled. Viewers who need larger text or higher contrast cannot adjust it. A second language means a second video. Burning in also requires re-encoding the whole video, which takes time and loses a little quality, and the text can collide with on-screen graphics or platform interface elements.

Editing, adding and extracting

Sidecar files are the easiest to change: open the SRT in a text editor or subtitle editor, fix the text or timing, save, and re-upload. The guide to editing an SRT file covers the details.

Embedding a sidecar into a video is a remux, not a re-encode, and takes seconds. Tools such as ffmpeg and MKVToolNix can add one or more subtitle files as tracks, set language codes and choose a default. MKV accepts SRT directly; MP4 requires converting the text to its own timed-text format, which some tools do automatically.

Extracting works in reverse. Text-based tracks can be pulled out of an MKV or MP4 as SRT or similar files with the same tools. Image-based tracks have to go through optical character recognition (OCR) to become text, with errors to correct. Burned-in subtitles are the hardest: getting text back means OCR on the video frames themselves, and removing them from the picture is generally not practical.

The guide to adding subtitles to a video covers the full workflow from file to published video.

Choosing by situation

• Uploading to a video platform or embedding on your own site: sidecar SRT or VTT files.
• Several languages in one deliverable for desktop playback or archiving: embedded tracks in MKV.
• Apple devices and players that read MP4 timed text: embedded MP4 tracks can work; test on the actual devices.
• Social feeds watched on mute, or a screener that must show text in any player: burned-in, from a copy of the master.
• Content you will keep correcting or translating: keep a sidecar master, whatever else you deliver.

Mistakes and trade-offs

• Burning subtitles into the only master. Always burn into a copy and keep the clean version.
• Uploading a video with embedded subtitles and assuming the platform will show them. Upload the caption file separately.
• Separating a sidecar from its video during handoff. Name files consistently and deliver them together.
• Embedding styled or image-based subtitles into MP4, where they may be dropped or ignored.
• Forgetting language tags on embedded tracks, so players show "Track 1" instead of a language.
• Saving sidecars in a legacy encoding that garbles accented or non-Latin characters.

What mydubly produces: sidecar files only

mydubly's subtitle generator produces sidecar files: SRT and VTT, encoded as UTF-8 with a byte order mark so that accented and non-Latin characters survive most players and editors. Each job gives one subtitle track, in the spoken language or in a target language, with one single-line cue per recognized segment, numbered in order. There is no styling, positioning, italics, sound tags or speaker labels.

mydubly does not burn subtitles into the picture and does not embed them as tracks. When you dub a video with the video translator, the translated video contains no subtitle track; the target-language subtitles that follow the dubbed lines come as separate files. If you want an embedded track or burned-in text, add the SRT or VTT with another tool afterwards. mydubly also cannot import an existing SRT or VTT file.

A subtitle job costs 1 credit per minute with a 5-credit minimum, so a 50-minute lecture costs 50 credits (5¢).

Next step

Keep a sidecar SRT or VTT as your master subtitle file for every video, because every other delivery can be made from it: upload it as is, embed it with a remux, or burn it into a copy. Decide per destination, and test playback on the devices your audience actually uses.