How to add subtitles to a video

The Captions tab does two things and charges nothing for either: it detects the speech in a video you upload, and it burns caption lines into the frames with local ffmpeg. Both run on our own hardware. The part that can cost money is the transcription step, and only sometimes — this page is straight about when, because it is the number nobody else spells out.

What the Captions tab does

Upload a video, press detect, and the speech comes back as timed lines you can edit before anything is rendered. Pick a style, a colour and a position, and the lines are burned into the frames with ffmpeg on our own server. The output is a new video file with the captions baked in — not a sidecar subtitle file, which is worth knowing if you wanted an .srt.

The editing step in the middle is the point. Automatic transcription is good and not perfect: proper nouns, brand names and overlapping speech are where it slips. Fixing four words before the burn costs nothing and is faster than rendering twice.

Which plan: The Audio Studio opens on the Starter plan. That gate lives on the server: every generating audio endpoint answers 403 to a free account, so it is not a greyed-out button you can work around. Everything behind these tabs runs on a paid provider, which means it is billed in ✦ gold credits — ⚡ green credits, the ones that refill daily, cannot pay for any of it.

How to caption a video

  1. Open the Captions tab. Go to /audio and pick Captions in the rail. Two modes sit at the top: Auto Captions, which transcribes, and Static Text, which burns one fixed line.
  2. Upload the video. MP4 or MOV. The transcription step accepts files up to 200 MB — a larger clip needs trimming or compressing first, and the interface says so up front rather than failing halfway.
  3. Detect the speech. This is the transcription pass. It returns timed lines rather than one block of text, so every caption already knows when it starts and ends.
  4. Fix the lines. Each line is editable in place before the burn. This is where names, jargon and numbers get corrected. Up to 500 lines are accepted in one video.
  5. Choose the look. Six styles, a colour picker, and a top, centre or bottom position. The preview frame above the controls updates live, using a real line from your transcript rather than dummy text.
  6. Burn it in. ffmpeg renders the captions into every frame on our own server. It costs 0 credits, and the finished file lands in your assets library.

The six caption styles

Each style can be recoloured and placed at the top, centre or bottom of the frame.
StyleWhat it looks like
CinematicLarge, bold, letter-spaced and uppercase, with a soft fade in and out
SubtitleClean lower-third captions, the conventional broadcast look
KaraokeBold and punchy, with a short fade as each line lands
TypewriterMonospaced, thin outline, no shadow
Neon GlowHeavy blurred outline, for vertical social cuts
MinimalSmall, light, no outline and no shadow at all

The honest part: transcription is not always free

Speech-to-text on this platform runs on our own self-hosted Whisper service, and while that service is answering it costs nothing. Pressing a microphone should not have a price on it. But it is a ladder, not a guarantee: when the local container is restarting or the GPU is busy, the request steps onto OpenAI's Whisper API, and past that onto a third provider.

Watch out: When transcription falls through to a paid provider it bills ✦1 gold per started minute of audio — and a free account holds no gold, so it cannot pay that. The burn-in itself stays free either way. Most of the time the local service answers and nothing is charged; the point is that free speech-to-text is true for the common case, not for every case.

A short mic press bills the one-credit minimum when it lands on the paid rung. A ten-minute video that has fallen through costs ✦10 for the transcription pass. Nothing is charged when a transcription fails: the balance check happens before the provider call and the deduction only after it returns.

Why the lines are burned in

A separate subtitle file is the better format in exactly one place: a player you control, where a viewer can switch captions on. Everywhere a short clip actually gets watched — a feed that autoplays muted, a repost, a file somebody drops into an editor — the subtitle track is either not read at all or left switched off. Burning the lines into the frames is the version that survives the trip.

The trade is that the text is permanent, and sized for the frame it was rendered into. If a clip is going out both wide and vertical, caption each crop separately rather than captioning once and re-cropping afterwards: a bottom-positioned line on a 16:9 master ends up outside a 9:16 cut.

Timing comes from the speech, so the lines are already in sync when they arrive. Editing the words does not move the timing, which is what you want when you are fixing a misheard name — but it also means a line you rewrite much longer stays on screen only as long as the phrase it replaced.

Static Text mode

The second mode has nothing to do with speech. Type a line, upload a clip, and the text is burned across the whole video in whichever of the six styles you picked. It is the fastest way to put a title, a handle or a call to action onto a vertical cut, and because it never touches transcription it is free with no conditions attached.

The numbers

LimitThe numberNote
Caption lines a video500Refused above this, with a message
Video size for the transcription step200 MBTrim or compress first
Burn-in cost0 creditsLocal ffmpeg, not a provider
Transcription cost0, or ✦1 a started minuteFree on our own Whisper; billed when it falls through
PlanStarter and upEnforced at the route

One consequence of the tab living inside the Audio Studio: the caption burn-in is free but not reachable free. A free account is refused at the endpoint along with everything else behind that gate, so the 0-credit price is a price for paid accounts.

Open the Captions tab — Opens the studio on Captions. Upload, detect, edit and burn all happen there.

Does adding subtitles cost credits?

The burn-in is 0 credits — it is local ffmpeg. The transcription that produces the lines is free while our own Whisper service answers, and bills ✦1 gold per started minute when it falls through to a paid provider.

Can I edit the transcript before it is burned in?

Yes, and you should. Every detected line is editable in place, which is where names and numbers get fixed. Up to 500 lines are accepted per video.

Do I get an .srt file?

No. Captions are burned into the frames and you get back a new video file. That is what social platforms and autoplay feeds need; it also means the text cannot be switched off later.

How big a video can I caption?

The transcription step takes files up to 200 MB. Beyond that, trim or compress the clip first — the interface refuses it with a message rather than failing part way through.

Can I caption a video on the free plan?

No. The Captions tab sits inside the Audio Studio, which is Starter and up and enforced by the server. The 0-credit burn-in price applies to accounts that can reach it.

Can I just put one line of text over a whole clip?

Yes — Static Text mode does exactly that, in any of the six styles, and it never touches transcription, so it is free with no conditions.