1. Add the video
Drop in an MP4, MOV, or WebM from your computer, or a file you exported from a longer edit. Nothing to install, and nothing to queue.
AUTO CAPTIONS
Captions that land on the word
Most people watch with the sound off. Null transcribes the audio, times every word, and drops the captions on the timeline, where you can still fix the one word it misheard.
Caption style · 20 looks
Aa Figtree · 800
WORD TIMED
Word timingEach word gets its own in and out point, not a block of text per line.
10 fontsFigtree, Montserrat, Anton, Bebas, Poppins, Inter, Archivo and more, with size and position.
20 stylesHighlight, animation, letter case, and background, per style. 15 on Starter, all 20 on Creator and Studio.
Still editableCaptions sit on the timeline. Retype a word, move a line, undo a change.
FROM AUDIO TO CAPTIONS
Four steps, then your edit
Captioning is the part that usually eats the afternoon. It should cost you one pass and a read-through.
2. Generate the captions
Null reads the audio and writes a word-timed transcript. Captioning does not spend export credits; only the final render does.
3. Pick the look
Choose a caption style, font, size, and position, and set how the spoken word is highlighted. A brand kit saves that look so every clip matches without setting it up again.
4. Read it once, then export
Fix names, jargon, and anything the transcript guessed at. Burn the captions into an MP4 or GIF — 1080p on any plan, 4K on Creator and Studio where your browser supports it — or save them as an SRT or VTT file for the platform to render.
WHAT LEAVES YOUR MACHINE
Audio excerpts, not your footage
To write the transcript, the editor sends short audio excerpts to a speech service (Cloudflare Workers AI). Your video file stays on your device, and the render happens there too. The privacy policy says exactly what is sent and who processes it.
If you would rather direct the whole thing from the AI app you already use, Null MCP exposes the same caption and cut tools to Claude, Codex, and Cursor.
Questions about captions
How accurate is the transcript?
Good enough to edit, not good enough to publish unread. Names, brands, and jargon are where it slips, so read the captions once before you export.
Can I edit the words after they are generated?
Yes. Captions are layers on the timeline, so you can retype a word, change a line break, move a caption, or delete one, and undo any of it.
Do captions cost credits?
No. Credits are spent on exports only — 15 per minute at 1080p and 30 per minute at 4K, rounded up. Cuts, captions, and previews spend nothing.
Can I get an .srt or .vtt file?
Yes. Save the captions as SRT or VTT for the platform to use, or burn them into the MP4 you export. You can also open an existing SRT or VTT file and edit it on the timeline.
Which plans include captions?
All of them. Starter has word-timed captions, 10 fonts, and 15 styles; Creator and Studio add the other 5 styles, 4K export, and the motion graphics library.
Null Motion
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