Wait, YouTube Subtitles Can Shake? Uncovering a Hidden World of Custom Captions

Did you know YouTube subtitles can do more than display text? An old, rarely-used caption format allows for hidden effects like shaking text and custom on-screen movement, a surprising piece of platform history demonstrated in a viral video by Tom Scott.

Wait, YouTube Subtitles Can Shake? Uncovering a Hidden World of Custom Captions

When you think of YouTube subtitles, you probably picture plain, static text at the bottom of the screen. They’re a crucial accessibility tool and a great way to watch videos on mute. But what if captions could do more? What if they could move, dance, and even shake to match the on-screen action? As it turns out, they can—or at least, they once could with much greater ease.

The "Shake, Rattle, and Roll" Discovery

For many, the first glimpse into this hidden feature came from a popular video by creator Tom Scott titled "This video has shaking text." In it, Scott calmly explains that he's enabled a special feature in the subtitles. As he says the words "shake, rattle, and roll," the corresponding captions tremble violently on screen, a bizarre and unexpected effect that left many viewers stunned and confused. The video quickly sparked curiosity, with viewers wondering if it was a video editing trick or a genuine YouTube feature.

The reaction online highlighted just how obscure this functionality was. On forums like Reddit, users expressed their surprise and immediately began brainstorming creative—and sometimes nefarious—uses for such a tool.

Oh my God. The horror-genre Let's-players are going to have a field day with this.

How It Works: The Magic of SubViewer 2.0

The secret lies not in a modern YouTube Studio setting, but in a legacy subtitle format called SubViewer (.sub). While YouTube now primarily defaults to formats like WebVTT, it has historically maintained support for older types, including this one. The SubViewer 2.0 format allows creators to embed simple styling and effect tags directly into the caption file.

To create the shaking effect, a specific tag is used in the .sub file:

{EFFECT:type=shake;level=3}shake, rattle and roll.

In this tag, the 'level' can be adjusted to control the intensity of the shake. But the customization doesn't stop there. The same format also supports tags for custom movement, allowing creators to make text slide across the screen:

{MOVE x1,y1,x2,y2,t1,t2}Moving text here...

This tag moves the subtitle from a starting coordinate (x1, y1) to an ending one (x2, y2) over a specific time interval, creating a simple animation effect. It's a far cry from the simple, static captions we're used to seeing.

A Relic of a Bygone Era?

If this feature is so interesting, why is it virtually unknown? The main reason is that it’s a remnant of an older web. Modern captioning standards, like WebVTT, have focused on universal accessibility and compatibility, stripping away proprietary, flashy effects in favor of consistency. As a result, support for these SubViewer effects is spotty at best. They may work on a desktop browser but fail on mobile apps, smart TVs, or embedded players.

Today, these dynamic subtitles exist as a fascinating easter egg—a piece of internet history embedded in YouTube's code. They represent a time of more chaotic and experimental web features, before standardization smoothed out the internet's quirkiest edges. While you're unlikely to see shaking text in your favorite creator's next video, its existence is a fun reminder that there are often hidden layers of technology right under our noses.

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