Video generatorConfigure here, generate in the appUpdated
Create viral vertical videos from a script or a prompt in minutes; starting from a URL is coming soon.
Start from a topic or a finished script, choose how the video should look and sound, and ShortFast produces a vertical video sized and paced for TikTok. No filming, no editing timeline, no design work.
Everything here also applies to Instagram Reels and YouTube Shorts, which share the 9:16 format. What differs between them is not the file, it's what each algorithm rewards, and that is worth understanding before you post the same video to all three.
How it works
A prompt if you want the script written for you, or your own narration if you've already written it. Both produce the same finished format.
Select the narrator. On TikTok, pace matters more than polish, a delivery that moves tends to hold better than one that sounds like an advert.
One of 27 styles: stock footage, AI-generated images, AI video, or mixed. Mixed suits most topics; pure AI visuals stand out more but read as synthetic if overused.
Vertical 9:16 with burned-in captions: the format TikTok's player is built for, and readable for viewers who watch on mute.
The finished video goes into your posting queue, so it can publish to TikTok, Reels and Shorts on a schedule rather than manually.
TikTok weights completion heavily. A 20-second video watched to the end generally travels further than a 60-second video abandoned at 40 seconds, even though the second one produced more total watch time. That makes length a strategic choice rather than a matter of how much you have to say.
It also re-tests content. A video that underperforms on day one can be picked up later, which is why deleting and reposting is usually counterproductive and why consistency beats individual optimisation.
Instagram Reels behaves differently: sends and saves carry more weight, which rewards content people forward to someone specific. YouTube Shorts gives a slightly longer runway in exchange for a clearer promise up front. Same video file, three different definitions of success.
Most TikTok viewing is sound-on, but some of it happens on mute or in places where audio isn't practical. A video that only works with sound loses those viewers in the first second, and first-second drop-off is the most expensive kind.
Burned-in captions solve this, and they do it better than uploaded caption tracks because they render identically everywhere and can't be switched off. ShortFast generates them from the same narration the voice reads, so they stay in sync.
The secondary benefit is accessibility, which is worth doing on its own terms and happens to overlap with what the algorithm rewards.
Short-form performance is heavily skewed. Most videos do modestly and a small number do disproportionately well, which means the number of attempts matters more than the average quality of any one of them. Posting once a week gives you very few chances to find the outlier.
This is the actual argument for generated video: not that it replaces good judgment, but that it makes it affordable to take enough shots for the distribution to work in your favour.
The failure mode is generating volume with no variation, twenty videos with the same opening pattern is one experiment run twenty times, not twenty experiments.
FAQ
Keep going
Publishing specs and scheduling in depth.
OpenFree toolFree openings built for TikTok specifically.
OpenFree toolCheck a handle before you commit to it.
OpenVideo generatorStart from a topic instead of a script.
OpenFeatureSeveral social accounts, one per platform in each profile.
OpenCompareGenerating new video vs clipping existing video.
OpenShortFast writes the script, generates the video, adds captions, and posts it to TikTok, Reels, and YouTube Shorts for you, every day.
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