Burn SRT subtitles into MP4 for TikTok

Standard TikTok burn with the tiktok preset

The everyday case: a vertical clip plus a hand-corrected SRT, burned with the TikTok preset so captions clear the in-app UI.

Inputs:
  dance-clip.mp4   1080x1920, H.264 + AAC
  dance-clip.srt   42 cues

Options:
  Subtitle file = dance-clip.srt
  Style preset  = TIKTOK

FFmpeg (effective):
  -i dance-clip.mp4
  -vf subtitles=sub.srt:force_style='FontName=Arial,FontSize=28,
      PrimaryColour=&H00FFFFFF,OutlineColour=&H00000000,BorderStyle=1,
      Outline=3,Shadow=1,Bold=1,Alignment=2,MarginV=80'
  -c:v libx264 -preset medium -crf 20 -c:a copy out.mp4

Output:
  dance-clip-out.mp4 — white bold captions, 80px off bottom

Keeping captions small with the default preset

If your SRT already has the look you want, or you want minimal text, the default preset applies no force_style and lets FFmpeg render the cues plainly.

Options:
  Style preset = DEFAULT

FFmpeg (effective):
  -vf subtitles=sub.srt        (no force_style override)

Result:
  Plain white text, thin outline, FFmpeg's default size
  and bottom position. Smaller and lower than the tiktok preset.

Captions sit behind the TikTok caption box

Symptom: burned text overlaps the username/description overlay. The tiktok preset's MarginV=80 is tuned for this; if it still clashes, the cause is usually the platform UI, not the burn.

Problem:
  Used DEFAULT preset -> text rendered low, behind UI.

Fix:
  Switch Style preset to TIKTOK (MarginV=80 lifts cues higher).

Note:
  This tool offers 5 presets, not free-form Y position.
  For a custom vertical offset, edit MarginV in an ASS
  file with the subtitles filter offline — out of scope here.

Fixing a typo without re-cutting the video

Captions are data; the SRT is plain text. Correct it in any editor and re-burn — the video is untouched until you re-run.

1. Open dance-clip.srt in Notepad / VS Code
2. Fix:  'Lets go'  ->  "Let's go"
3. Save (keep .srt extension)
4. Re-pick the SRT, keep preset = TIKTOK, Run

Result: corrected caption, identical video + audio,
        ~seconds of re-encode.

Reframe first, then burn

If your source is 16:9, crop to vertical before burning so captions are positioned for the final 9:16 canvas — the burner reads bottom margin from the frame it receives.

Pipeline:
  1. /video-tools/auto-reframe  (16:9 -> 9:16 smart crop)
  2. Re-time / verify the SRT against the cropped clip
  3. Subtitle Burner: preset = TIKTOK

Why order matters: MarginV=80 is measured from the
9:16 frame's bottom, so reframing first keeps captions
in the safe zone.

A subtitle track muxed alongside the video (soft subs) is removed when TikTok re-encodes on upload — viewers see no captions. This tool avoids that entirely: it paints the cues into the frame via the subtitles filter, so the text is pixels, not a removable stream.

The burner renders cues at exactly the timestamps in your SRT; it does not re-sync. If captions lead or lag, fix the timing in your SRT (a constant offset is a quick find/replace on the 00:00:00,000 stamps) and re-burn.

Format is chosen by extension: only names ending .vtt are read as WebVTT; everything else is parsed as SRT. A correctly-formatted SRT saved as .txt will be treated as SRT, but a mislabelled or malformed file makes FFmpeg's subtitles filter fail. Keep the real .srt/.vtt extension and content matched.

The run throws Pick an .srt or .vtt file. if the subtitle slot is empty. The burner needs both the video and a caption file — there is no auto-transcription step in this tool.

The tiktok/subtle presets use Arial; bold uses Impact; youtube uses Roboto. Glyphs missing from the chosen font render as tofu boxes. For CJK, Arabic, or heavy emoji, the default preset (which leans on FFmpeg's bundled fontconfig defaults) is the safest, and you may need to confirm coverage before publishing.

-c:a copy simply has nothing to copy on a silent clip — the burn still succeeds and produces a video-only MP4. No error is raised.

Free tier allows 1 GB per file and one file at a time. A long 4K source can exceed that; Pro raises the ceiling to 10 GB and Pro + Media to 100 GB with streaming. There is no minutes limit — only file size and batch count.

If your tier allows multiple files, the burner processes them as a batch, applying the same selected SRT and preset to each. That is rarely what you want for distinct clips — burn each clip with its own matching SRT one at a time for correct captions.

Burning requires one re-encode (you can't paint text without re-drawing frames). CRF 20 is visually lossless for most footage; TikTok then re-compresses again, so starting from a clean CRF 20 master gives the platform good source pixels to work from.