TikTok auto captions or burned-in captions on an AI video?

TikTok's auto captions are a feature viewers switch on; they come from speech, so they do nothing for a silent or music-only AI clip. Burned-in captions are pixels in the MP4, so they show for everyone and carry your wording and style. For a finished AI video, burn captions with Sume ($0.20 per clip up to 60 seconds) and let TikTok's own captions cover the rest.

TikTok's 2022 newsroom post describes the two features: auto-generated closed captions that creators and viewers can use, and translations of captions, descriptions, and text stickers. It says they were in early rollout with an initial set of nine languages: English, Portuguese, German, Indonesian, Italian, Korean, Mandarin, Spanish, and Turkish. That list is four years old, so check what the app offers now.

Where each one wins

Burned-in captions on Sume

Video captions takes a public HTTPS video_url and burns captions in. If you omit style, Latin text defaults to slam and Korean to black-outline. tiktok-green is a named style. language is only a speech-to-text hint and never selects the style or font.

If you give script_text, Sume keeps the STT word timings and aligns your text to them, and the job can fail with script_alignment_mismatch if the script and speech disagree. Send source_caption_id instead of video_url to restyle without transcribing twice.

A practical split

Burn captions when the clip depends on the words: dialogue, a price, a disclosure line. Rely on TikTok's captions for accessibility and translation, since viewers can read them in their own language. Make sure the burned text sits clear of the app's buttons; the anchor-ratio post explains how to place lines.

A burned-in AI disclosure also helps on the label side: TikTok's 2023 label post describes the toggle, and the Shop pages accept an on-screen note as an alternative way to disclose.

Cost and effort

Burning captions on every clip adds $0.20 per job for clips up to 60 seconds, so a month of 30 posts adds $6. That is small next to the render cost, but it is not free, and you can skip it for clips where TikTok's captions will do. If you restyle a clip, use source_caption_id so you do not pay to transcribe it again.

Check one more thing before you burn: if the language is Korean, use a Hangul style, since Korean on a Latin style returns a 400 error.

Check the result on a phone, not only on a desktop preview. Captions that fit a 16:9 window can sit under the TikTok caption, username, or buttons on a 9:16 screen. Keep the burned text in the middle band of the frame and re-render if a line is covered.