Tutorials
How to Add Subtitles to Video Online (Soft Track or Burn-In)
Mux SRT, VTT, ASS, TXT, or SBV subtitles into MP4 — as a selectable track or hard-burned into the picture.
Accessible video needs captions - but delivery format matters. Some platforms want a soft subtitle track viewers can toggle; others need hard-burned text baked into pixels. Add Subtitle to Video muxes TXT, SRT, VTT, ASS, or SBV into MP4 on your device, with optional burn-in.
Soft track vs hard burn-in
| Mode | Viewer experience | Processing |
|---|---|---|
| Soft track (default) | Subtitles on/off in supported players | Faster mux |
| Hard burn-in | Text always visible | Slower re-encode |
Choose soft tracks for YouTube uploads and accessibility compliance where players support sidecar or embedded tracks. Choose burn-in for Instagram, some email players, or when you must guarantee text visibility.
Step-by-step: add subtitles to MP4
- Open Add Subtitle to Video and add your MP4 video plus a subtitle file from your device.
- Confirm subtitle format is detected (convert first with Subtitle to SRT if needed).
- Leave Hard subtitle burn-in off for a selectable track, or enable it to render text into the image.
- Click Add Subtitle & Download.
- Test in your target player - toggle subtitles on soft exports; verify readability on burn-in exports at phone size.
All processing is local.
Accessibility and platform notes
Soft subtitles help hearing-impaired viewers and silent autoplay environments when players expose CC toggles. Burn-in guarantees visibility on platforms that strip metadata tracks (some social apps and messaging players).
YouTube generally prefers uploading a separate SRT in Studio for long-form videos; burn-in is common for Shorts reposts to Instagram where you want baked captions.
Test one minute of output on the lowest-end phone you support - burn-in font size is not re-flowed per device.
Preparing subtitle files
- Normalize to SRT when editors export messy VTT/SBV - Subtitle to SRT fixes many syntax issues.
- Match timeline - subtitle duration should align with the video; trim video or edit cues if drift appears.
- Line length - long lines may wrap awkwardly on burn-in; preview on mobile mentally.
ASS styles partially flatten on conversion - burn-in preserves more visual intent if you rely on positioning.
Delivery checklist by platform
| Destination | Practical approach |
|---|---|
| YouTube long-form | Soft SRT upload in Studio plus optional embedded track from this tool |
| Instagram / TikTok reposts | Burn-in so captions survive re-encoding |
| Internal review | Soft track so stakeholders can toggle off |
| Email attachments | Burn-in — many desktop players ignore subtitle tracks |
Export two masters when budget allows: a burn-in social cut and a soft-subtitle archive for future re-edits. Social platforms re-encode aggressively; thin fonts that read on desktop may vanish on a phone in sunlight.
If cues reference on-screen graphics ("as shown here"), scrub those moments before burn-in — text overlapping UI becomes unreadable at small sizes.
SDH (closed captions with sound cues) may need manual [music] or [applause] lines — automation from raw SRT rarely adds those; edit the file before burn-in.
Tips
- Burn-in is final - viewers cannot disable text; keep a soft-subtitle master if possible.
- One language per pass - add extra tracks in advanced tools if you need multiple languages.
- Compress after - burn-in re-encodes video; avoid chaining unnecessary Compress Video passes.
Common issues
Burn-in takes very long. Expected - every frame is re-rendered with text.
Subtitles out of sync. Fix timecodes in the SRT source or adjust video start with Trim Video.
Player shows no subtitle menu. The player may not support embedded tracks - use burn-in for that target.
Frequently asked questions
Which subtitle formats are supported?
TXT, SRT, VTT, ASS, and SBV as listed in the tool.
Can I add multiple languages?
One file per run - repeat with separate subtitle files if needed.
Related tools
- Subtitle to SRT - normalize caption files first
- Trim Video - align video length with cues
- Compress Video - reduce size after subtitling