How to Glitch Part of a Video with Rectangle & Ellipse Masking
Applying a glitch effect to an entire frame is a great way to set a mood, but sometimes you want the chaos to be intentional and localized. Whether you are highlighting a specific object, obscuring a face, or creating a high-tech 'HUD' look, masking is the tool for the job.
The Power of Selective Distortion
Full-screen glitches can sometimes overwhelm the viewer or hide important details in your footage. Masking allows you to maintain the integrity of your subject while adding visual interest to the periphery—or vice versa. By isolating effects to a Rectangle or Ellipse, you create a focal point that feels professionally designed rather than accidental. This technique is particularly effective for social media content where you want to draw the eye to a specific element without losing the overall aesthetic of the video.
The Kaleidoscope Preset: A Geometric Foundation
When working with shapes, the Kaleidoscope preset is the perfect starting point. Because masking uses geometric boundaries, the prismatic, repeating nature of the Kaleidoscope effect complements the sharp edges of a rectangle or the soft curves of an ellipse. It transforms your masked area into a digital prism, refracting the colors and shapes within the video into something surreal.
To make the look your own, you can nudge the RGB Split knob to increase the 'fringing' at the edges of your mask, making it feel more like a physical lens error. If the effect feels too dark or heavy, adjusting the Contrast and Color Boost knobs can help the masked area pop against the original footage. The Hue Shift dial is also essential here; use it to rotate the colors of the distortion so they either match your background or provide a jarring, high-contrast accent.
How to Apply Masks in Glitchest
If you have ever used professional tools like Adobe Premiere Pro or DaVinci Resolve, you know that masking usually involves 'Power Windows' or 'Opacity Masks.' While those tools are powerful, they often require multiple menus and keyframing paths. In the editor, masking is streamlined into a few clicks:
- Load Your Media: Drag your video into the browser. Remember, nothing is uploaded to a server; your data stays local and private.
- Select the Kaleidoscope Preset: This will apply the effect to the whole screen initially, giving you a clear view of how the colors and distortions look.
- Toggle Masking: In the effect settings, choose between the Rectangle or Ellipse mask. An outline will appear on the preview screen.
- Position and Scale: Drag the mask handles to cover the specific area you want to glitch. If you want to obscure a person's face, the Ellipse is your best friend. For a glitchy sidebar or 'screen-within-a-screen' look, go with the Rectangle.
- Set the Timeline: Unlike traditional editors that use a 'timeline curve' to animate intensity, Glitchest uses effect boxes. Drop an effect box onto the timeline for the duration you want the mask to appear.
Mastering the Effect-Box Timeline
To create a dynamic look, you need to think in terms of placement and fades. If you want a mask to 'hit' suddenly and then vanish, place a very short effect box on the timeline. If you want the distortion to grow into view, select the box and increase the fade-in slider. This creates a smooth transition without ever having to manually draw a curve.
You can also layer boxes on different lanes. For example, you could have a rectangular mask on Lane 1 for the duration of the clip, and then drop a series of short, high-intensity 'glitch hits' on Lane 2 that use an Ellipse mask in a different corner of the screen. This layering creates a complex, professional-grade composition in seconds.
Comparing the Workflow
In After Effects, creating a localized glitch involves drawing a path with the Pen Tool, applying an effect like 'CC Kaleidoscope,' and then using a track matte or adjustment layer. It offers infinite control but requires a significant time investment and a high-end computer to render. CapCut and other mobile editors often provide 'filters' with masks, but they rarely give you the granular knob control found in a glitch effects for beginners tool like Glitchest.
Glitchest bridges the gap. It gives you the specific knobs to refine the distortion—like the Kaleidoscope intensity dial—while keeping the masking interface as simple as dragging a box. Because it uses WebCodecs, you can export your masked masterpiece as an MP4 directly from your browser without waiting for a cloud server to process it.
Refining the Look with Time Machine
Once your masked glitch is perfectly placed, consider the overall texture of your video. If the masked area looks 'too digital,' use the Time Machine dial. This knob ages the entire frame, adding a film-like grain or VHS-style softening that can help blend your masked Kaleidoscope effect into the original footage. It provides that final 'glue' that makes your isolated mask feel like a natural part of a corrupted video stream.
The exact settings
Start from the Kaleidoscope preset, then set:
| RGB Split | 28 |
| Hue Shift | 42 |
| Color Boost | 56 |
| Contrast | 54 |
| Kaleidoscope | 82 |
Everything else stays at its default — tweak it, then copy your own look as JSON or a link from inside the editor to share it.
Try it now — add this look to your own clip, free and in your browser.
Open the editor →FAQ
Can I apply different glitch masks to the same clip?
Yes, you can stack multiple effect boxes on different lanes in the timeline, assigning each a unique mask shape and position.
How do I make a glitch mask appear and disappear smoothly?
Instead of drawing curves, simply set the fade-in and fade-out sliders on your effect box to transition the mask in and out of the scene.
Is it possible to track a moving object with the mask?
Glitchest uses static masks per effect box; for moving objects, you can place multiple short effect boxes in succession, moving the mask position slightly in each one.