Auto captions for YouTube Shorts

What YouTube's own automatic captions do

YouTube's help page on automatic captioning is explicit that they work on long-form videos and on Shorts, in a listed set of languages that includes English, Hindi and Spanish. It also says they come from machine learning, that quality varies, and that you should always review and edit them. English automatic captions can add expressive details such as sounds like sighs and gasps.

That makes the YouTube route a reasonable first pass for anything you publish on YouTube alone. The limit is what it is: a caption track belongs to the YouTube video. If you download the Short and post it to another app, do not expect the track to come with it. And the look is whatever the player draws. The W3C notes that styling and positioning support in players is inconsistent, and that most web video uses the player default, usually white characters in a black box.

Burned-in captions: what changes for a Short

A word of caution if you use both: a viewer who switches on YouTube's track will see the burned-in words and the track's words together. If you want one look, pick one. Burned-in is the choice when the style is part of how you want the clip to feel.

Burned-in captions are what the W3C and WCAG call open captions: always displayed and impossible to turn off. The tradeoff is that the words have to be right before you export. See adding subtitles permanently for the full comparison.

Basics a captioned Short has to meet

• Length: YouTube Help says Shorts can be up to 3 minutes.
• Shape: from 15 October 2024, videos on standard channels that are square or vertical and up to three minutes are categorised as Shorts. A 16:9 video is not.
• Resolution: Shorts can be uploaded at a maximum of 1080p. YouTube's pages we read do not state a vertical pixel size such as 1080x1920 for Shorts.
• Safe areas: no pixel safe zone for captions on Shorts appears in the YouTube help pages we read. Export a clip, view it in the YouTube app on a phone and look at where the interface covers the picture before you commit to a placement. The safe zone checker is a quick first look.

Getting burned-in captions onto Shorts with KeyMo

KeyMo returns up to 15 vertical clips from a long video, each 15 to 90 seconds in Auto mode, at 1080x1920 and 30 fps, so they fit well inside YouTube's three-minute limit. Each clip gets word-by-word captions in one of 12 styles. You upload an MP4 or MOV (5 minutes to 3 hours), or paste a YouTube link on a paid plan and confirm that you own the video or have permission.

Clips score out of 10 and only 7 or higher are kept, so a weak episode returns fewer. Download them one by one or as a single ZIP, then upload to Shorts. There is no watermark on any plan.

On cost: KeyMo has no free plan and no trial, so a free YouTube Shorts caption generator is not what this is. Starter is $12 a month for 300 source minutes and Pro is $29 for 900. If you only need YouTube's built-in captions on a Short you already have, you do not need KeyMo for that.

To pick a look, see the caption styles gallery. For the Instagram side of the same clip, read auto captions for Reels.