What Is Onion Skinning? A Practical Guide

What is onion skinning?

Onion skinning is a feature that shows faint, ghosted copies of the frames around the one you are currently drawing. Instead of working blind, you can see where your subject was in the previous frame — and often where it will be in the next — layered underneath your active frame like translucent tracing paper.

That single piece of visual feedback transforms frame-by-frame work. It lets you judge spacing — how far to move each element from one drawing to the next — and keeps your character on model, because you are always drawing in relation to what came before rather than guessing from memory.

Where the name comes from

The term is borrowed from traditional hand-drawn animation. Animators worked on thin, semi-transparent paper stacked on a backlit desk, so the drawings beneath showed through like the translucent layers of an onion. Digital onion skinning recreates that backlit stack — without the paper, the light table, or the smudges.

Why it matters

Onion skinning solves three problems that every beginner runs into:

• Consistent placement. You can see exactly where a limb, eye or edge sat in the last frame, so shapes do not drift or wobble unintentionally.
• Controlled spacing. Because the previous frame is visible, you can deliberately place the new one closer (slower motion) or further away (faster motion).
• Staying on model. A character keeps the same proportions frame to frame when you are always drawing against a reference.

Reading the ghost frames

The ghosted frames are usually dimmed or tinted so you can tell them apart from your active drawing. A common convention is to think of them by direction: the frame behind you (the one you just drew) and the frame ahead of you (the one you are moving toward). Seeing both at once lets you place the current drawing so it flows naturally out of the last pose and into the next.

The fainter a ghost, the further it is from your current frame. Seeing two or three frames in each direction is useful for smooth arcs; too many at once becomes a cloud of lines that is hard to read.

Using onion skinning in FrameAnim

FrameAnim has onion skinning built into the timeline, so you can reference neighbouring frames as you draw. The workflow is straightforward:

1. 1
   Enable onion skinning

   Turn on onion skinning from the timeline controls. Faint copies of the surrounding frames appear beneath your current frame.
2. 2
   Add a new frame

   Add or select the frame you want to draw. The previous frame shows through as a ghost to guide you.
3. 3
   Draw against the ghost

   Use the ghosted drawing as a reference for placement, then move each element the right distance for your spacing.
4. 4
   Check the motion

   Play the animation to confirm the spacing reads well, then move to the next frame and repeat.

Pair onion skinning with the timeline's ability to add, duplicate and reorder frames and you have everything you need for clean frame-by-frame work. If the ghosts ever become distracting during playback, simply toggle the feature off to see a single frame clearly.

A registration workflow

"Registration" means keeping your drawings aligned from frame to frame. Onion skinning is the tool that makes it possible. A dependable routine looks like this:

1. 1
   Draw a strong first frame

   Establish your character or shape clearly. This becomes the anchor everything else references.
2. 2
   Duplicate, then modify

   Duplicate the frame and change only what moves. With the ghost visible, you shift each element by the right amount instead of redrawing from scratch.
3. 3
   Watch your spacing

   Place the new drawing closer to the ghost for slow motion, further for fast motion. This is where spacing lives.
4. 4
   Play often

   Loop the animation regularly. Onion skinning shows you the frames; playback shows you the motion.

This is the exact approach used in the walk cycle tutorial, where each pose is registered against the last so the character does not slide or pop.

Common mistakes

• Showing too many frames. A dozen ghosts at once is visual noise. Keep it to a frame or two in each direction for most work.
• Tracing instead of moving. Onion skinning is a guide, not a stencil. If you copy the ghost exactly, nothing moves. The point is to offset each element deliberately.
• Leaving it on during review. To judge a single frame's artwork, toggle onion skinning off so the ghosts do not muddy what you are looking at.
• Ignoring spacing. Seeing the previous frame is only half the job — you still have to decide how far to move. Even spacing will look mechanical no matter how well registered it is.

Practise with it

The best way to appreciate onion skinning is to animate something that depends on precise spacing. Turn it on and work through the bouncing ball tutorial — you will feel how much easier it is to place each frame when you can see the last one. For the bigger picture of how frames become motion, revisit the frame-by-frame animation guide, or study finished loops on the animation examples page.