Timeline Panel

The time-based heart of the editor: arrange layers in time, scrub and play back, and edit animation. One panel, three modes — Layers, Keys (dope sheet), and Graph — sharing a ruler, playhead, and work area.

The Timeline sits in the bottom-left of the editor. It has a fixed top toolbar (transport + mode switch), a left panel that changes with the mode (layer list / param list), and a scrollable tracks area on the right with a ruler across the top.

Modes

Three modes, switched by the segmented control in the toolbar or by pressing Tab (cycles Layers → Keys → Graph):

Mode	Label	Left panel	Tracks show
Layers	Layers	Layer list (eye / blend / matte)	Clip bars + keyframe diamonds
Dope Sheet	Keys	Param list	Keyframes as a grid of diamonds
Graph Editor	Graph	Param list + Node/Layer/Comp scope	Animation curves

The ruler, playhead, work area, and horizontal view (zoom and scroll position) are shared across all three — switching modes keeps the same range of frames on screen.

Toolbar

Left to right:

• Composition settings (gear) — opens the comp dialog (also Cmd+K).
• Go to start — jump the playhead to frame 0.
• Play / Pause (Space) — real-time playback, or RAM-preview playback when RAM mode is on.
• RAM Preview toggle — switch between real-time and cached playback (see RAM preview).
• Time display toggle — switch the playhead readout between frames and timecode.
• Playhead field — the current frame/timecode; click to type an exact value and jump there.
• Work area toggle — set or clear the work area (preview range) to the full comp.
• Mode tabs — Layers / Keys / Graph (or Tab).
• Auto-key toggle (K) — when ON, editing an animated param auto-creates a keyframe; when OFF, edits are temporary and revert on playhead move.
• Clear cache — resets the caches and re-renders the current frame.
• Zoom out / in — also plain scroll wheel over the tracks (+ / - keys too). The zoom-out range adapts to the composition's duration, so even very long comps can be zoomed out to fit. Fit snaps the view to the whole comp duration in one click.
• Render — opens the export dialog. Also available as File → Export… (Cmd Shift E) — handy on small screens where the toolbar runs out of room, and it works even with the timeline panel closed.

In Layers mode an extra contextual group appears (duplicate selected layers, etc.).

Layer list (Layers mode)

The left panel lists the comp's layers, topmost first. The divider between it and the tracks is draggable to resize (240–500px). Each row has:

• Eye — enable/disable the layer (hidden layers don't render or composite).
• Motion blur — per-layer temporal-supersampling toggle (uses the comp's shutter settings).
• Blend mode — dropdown (Normal / Add / Multiply / Screen / Overlay) setting how the layer composites over the layers beneath it.
• Matte — dropdown to pick a track-matte source layer plus an Alpha / Luminance toggle. The matte source layer is excluded from normal compositing (standard track-matte behavior) and shows an M badge.
• Name — double-click to rename.

Selection

• Click — make the layer active (drives the node graph + Properties) and replace the selection.
• Cmd-click — toggle a layer in/out of the multi-selection.
• Shift-click — range-select from the active layer to the clicked one.
• Marquee — drag on empty track space to box-select.

One layer is active at a time — it's the layer the node graph and Properties panel follow. You can also have several layers selected at once for batch actions like sliding, duplicating, or deleting them together. Clicking a layer (in the list, on its track, or in the node-graph background) also selects its transform, so the on-canvas gizmo, Properties, and node graph all agree on what you're editing.

Tracks & clips (Layers mode)

Each layer is a clip bar spanning its start → end on the timeline.

• Drag the body — slide the clip in time. Sliding moves the layer's keyframes with it (so the animation travels with the clip).
• Drag an edge (trim) — change the in/out point. Trimming does not move keyframes — it reveals/hides source by adjusting the layer's source offset.
• Keyframe diamonds — animated params show their keyframes as diamonds along the clip.

Keyboard equivalents (timeline focused):

• [ / ] — slide the active (or selected) layers so the in / out point lands on the playhead, preserving duration; keyframes ride along.
• Alt+[ / Alt+] — trim the in / out point to the playhead (duration changes; keyframes stay).

Nesting compositions

Drag a composition from the Assets panel onto the tracks to nest it: the drop creates a layer wired Comp Source → Output, named after the composition and trimmed to its duration (converted to this comp's frame rate). The nested comp plays from its first frame at the layer's in-point, so trimming, sliding, and offsetting the clip work exactly like a video clip. Select the layer and use Open next to the Composition picker in Properties to edit the nested comp; changes show up everywhere it is used. If the nested comp has sound, the drop also wires the Comp Source's Audio output into the layer's Output, so its audio plays and exports through the layer, following the clip and the layer's Audio Gain, Pan, and Mute; disconnect that wire to nest the picture alone (no waveform is drawn for nested audio yet). See Comp Source for time modes and clipping rules.

Layers past the comp end

Layers may slide or trim beyond the comp's last frame (capped at 2× the comp duration so the scrollable width stays bounded). Frames past the comp end are dimmed and marked with a thin vertical line through the ruler and tracks. Layers out there are visible on the timeline but render nothing — the comp only renders its own frames, from frame 0 up to its duration. This is what lets [ put a full-length layer's in-point on a playhead deep inside the comp (its tail just spills past the end).

Ruler, playhead & work area

• Ruler — frame ticks and labels across the top; click or drag anywhere on it to scrub the playhead. The label density adapts to zoom.
• Playhead — a vertical line at the current frame. It stays within the comp, from frame 0 to the last frame.
• Page Up / Page Down — step the playhead back / forward one frame (global).
• Cache indicator — thin bars under the ruler show which frames are cached, colored by the resolution they were rendered at: green = Full, light blue = 1/2 Preview, gold = 1/4 Draft. RAM preview bars follow the same coding — they show the quality the preview was cached at. The viewer's quality dropdown uses the same colors, so during Auto-quality playback you can see exactly which spans hold which resolution — and why. Picking a manual quality drops cached frames from other tiers so the viewport always shows the resolution you asked for.
• Work area (preview range) — a lighter band on the ruler with drag handles (left/right to resize, middle to slide). The region outside it dims. Sets the range for RAM preview and looped playback. Keyboard:
  • B — set work-area start to the playhead.
  • N — set work-area end to the playhead.
  • The work area always stays clamped inside the comp.

Note: in Keys / Graph mode with keyframes selected, B sets the selected keyframes to Bezier (the H/L/S/B interpolation shortcuts). With no keyframes selected, B sets the work-area start.

Playback & RAM preview

• Real-time — plays at the comp frame rate, rendering on the fly at adaptive (usually Preview) quality. Skips frames to keep up.
• RAM preview — caches frames over the work area at the current viewer quality (Full when idle), then plays them back at native frame rate (4 GB budget). Numpad 0 triggers caching; Space toggles play/pause while keeping the cache. Editing the project resets the RAM preview.

Keys mode (Dope Sheet)

A compact grid of keyframe diamonds, one row per animated param, aligned with the param list on the left (collapsible layer headers).

• Select keyframes by clicking or marquee; a selection box around 2+ keys can be dragged to slide them or edge-handled to scale their timing.
• Interpolation of selected keys: H Hold · L Linear · S Smooth · B Bezier.
• Handle mode of selected keys: 1 Auto · 2 Clamped · 3 Free.
• Copy / Paste — Cmd/Ctrl C copies the selected keyframes (or, with a param row selected and no keyframes, the row's whole keyframe set); Cmd/Ctrl V pastes with the earliest key landing on the playhead, relative offsets preserved — including offsets between params when keys from several params were copied. Also available from Edit → Copy / Paste and the keyframe right-click menu ("Paste at Playhead").
• Where a paste lands — keyframes travel between like-type nodes. With nothing else selected they paste back onto their own params. Select a different layer (or several) and the keys land on the matching parameter of the same node type there — position from one Transform 2D onto another layer's Transform 2D, a Blur radius onto another layer's Blur. Select nodes in the node graph and each selected match receives the keys. Select param rows in the list and the rows are the targets: a row with the same parameter takes it, and when a single param was copied any row of the same value type does too (position onto scale). Rows of a different value type are left alone. Pasted keys are selected afterwards, and the whole paste is one undo step.
• Copy Ease / Paste Ease — Cmd/Ctrl Shift C copies only the easing of the selected keyframes (interpolation, handle mode, in/out bezier handles); Cmd/Ctrl Shift V applies it to the selected keyframes, in frame order, repeating a copied pair across every selected pair. Values and timing are untouched, so one hand-tuned ease can be stamped across any number of curves. Auto handles are copied as the shape they resolve to.
• Right-click selected keyframes for a context menu: interpolation, Copy, Paste at Playhead, Copy Ease, Paste Ease, ease presets (and Delete in the graph editor).
• Delete / Backspace removes selected keyframes.
• Keyframes can sit at or beyond the end of the clip/comp — drag them onto (or past) the clip boundary; values past the last keyframe hold, and data beyond the end survives if the clip is later extended.

Graph mode (Graph Editor)

An SVG curve view of animated parameters.

• Left panel scope — a Node / Layer / Comp selector chooses which params' curves are shown; a "Params" toggle narrows to the active param.
• Curves — every visible param is a colored curve; the active param's curve is slightly thicker. Colors default by component (X red, Y green, etc.); click the swatch next to a curve in the left panel to recolor it from the tag palette (or Default to restore the automatic color). Saved with the project.
• Keyframes — drag to move (frame + value); double-click empty space to add one; marquee to select.
• Tangent handles — selected Bezier keyframes show in/out handles you can drag. Handle modes: Auto (Catmull-Rom), Clamped (auto, Y-clamped), Free (manual). Bezier is symmetric — a segment eases if either endpoint is Bezier, and each endpoint contributes its own handle.
• Joined handles — a keyframe's in and out handles are joined by default: drag one and the other rotates to keep the curve smooth through the key, keeping its own reach into its segment. Hold Alt/Option while dragging to split them and move one side on its own; the split sticks to that keyframe (its handle dots turn into hollow squares) so later drags keep moving one side. Join Handles / Split Handles in the right-click menu do the same without dragging; setting a key back to Auto or Clamped (1 / 2) also rejoins it. On a flat segment (both keys at the same value) the handle on that side stays flat — it can't tilt to follow the other side.
• Multi-key handle drag — with several keyframes selected, dragging one handle applies the same change to the same-side handle of every selected Bezier key, measured relative to each key's own segment, so a batch of eases moves together whatever their value ranges.
• Ease presets — a menu applies Identity / Ease In / Ease Out / S-curve to the selection.
• Copy Ease / Paste Ease — Cmd/Ctrl Shift C / V (also in the right-click menu) copies the selected keys' handles and interpolation and stamps them onto other selected keys, per pair. See Keys mode above.
• Vertical zoom — Alt+scroll zooms the value axis; the value-scale edges can be dragged.

Value / Speed

A Value / Speed toggle (top-left, matching the scope selector) switches the Y axis:

• Value — the parameter's value over time (the normal curve).
• Speed — how fast the parameter is changing (its velocity), drawn as a curve with a shaded "hill" beneath it. The Y-axis label and a clearly-filled toggle indicate which mode you're in.

In Speed mode, selected Bezier keyframes show velocity handles: drag vertically to set the speed at that keyframe, horizontally to set the influence (how far the ease reaches into the segment). These map straight back to the same Bezier tangents the Value graph edits, so the two views stay in lockstep. Joined handles hold here too: dragging one side's speed carries the other side with it (a joined key has one speed through it), Alt/Option splits, and a multi-key selection drags together. The speed=0 baseline floats just above the bottom edge so at-rest handles stay easy to grab. Keyframe markers in Speed mode are select-only — retiming and adding keyframes are Value-graph operations.

Reverse keyframes

The toolbar's reverse action mirrors the selected keyframes' timing around their own range (first ↔ last), reversing the motion.

Keyboard shortcuts

The timeline shortcuts (and all others) live in docs/keyboard-shortcuts.md. Quick reference:

Key	Action
Tab	Cycle Layers / Keys / Graph
Space	Play / pause
Page Up / Page Down	Step playhead back / forward one frame
[ / ]	Slide layer in / out point to playhead
Alt+[ / Alt+]	Trim layer in / out point to playhead
B / N	Set work-area start / end to playhead
K	Toggle auto-key
+ / -	Zoom in / out (or scroll wheel)
H / L / S / B	Keyframe interp (Hold/Linear/Smooth/Bezier) — Keys/Graph with keys selected
1 / 2 / 3	Handle mode (Auto/Clamped/Free)
Delete / Backspace	Delete selected keyframes (or active layer)