Effects change how a clip looks: soften it, colour it, break it up, draw over it. You add them to a clip, adjust them while the preview follows, and animate them like any other setting. Every effect has its own page in the Effect catalog.
Try it interactively: Info → Tutorials → Effects & Color.
Select a clip in the timeline and open Properties → Effects. Click + Add Effect, type part
of a name (for example blur) or pick a group, then click a tile. The tiles preview each look on
your own clip, so you can compare before you choose. Effects whose name matches your search come
first. A tile marked Detail shows the middle of the picture at full size, because the effect's
lines, grain or characters are too fine for the small tile. No visible change means that the
effect, at its default settings, leaves the current frame as it is.
On an Adjustment Layer the list offers every effect that can change the layers below it. A few need a clip of their own, such as Slit Scan, the tracking effects and AI Edge Fill; the list names them under the tiles, and if one is on the layer anyway its card says why it is skipped. Effects marked Experimental in the list work, but have known flaws; their card says which.
The new effect appears as a card below the list. Drag a number left or right, or double-click it to type a value. The reset arrow (or a right-click on the number) brings back the default.
Some settings show a warning under the card, for example when a keyframe pushes a value past what the effect can draw: the card then says which value it uses instead.
Click the checkmark in the effect's header (Bypass effect) to switch the effect off without losing its settings: the card dims and the preview shows the clip without it. Click again to switch it back on. The red × removes the effect.
Example footage: © 2008 Blender Foundation / Big Buck Bunny, CC BY 3.0. Screenshots show an excerpt resized for the demonstration; the enabled example adds Gaussian blur.
A clip's effects work from top to bottom: the first card changes the clip's picture, every next card changes the result of the cards above it. So the same two effects can give two different looks. Pixelate then Glow makes the squares glow; Glow then Pixelate turns the glow itself into squares.
To change the order, drag a card by its ☰ handle to a new place. Pixel Particle Disintegrate always works last: effects below it have no effect. A colour grade from the Color tab also appears in the list, as Color.
Click the diamond next to a setting to set a keyframe at the playhead, move the playhead, and change the value: the effect now changes over time. Everything about keys, easing and curves: Keyframes.
To give other clips the same effects, right-click the clip in the timeline and choose Copy Effects, then right-click the other clips and choose Paste Effects. Their keyframes come along.
Some settings, such as Gaussian Blur's Radius or Hue Shift's Shift, have a small source icon (two dots joined by a line) before their keyframe diamond. Instead of a fixed number or keyframes, a small node can drive the setting: a slow wobble, random drift, the playing time, or the loudness of a sound clip. Click the icon, open the Source menu and choose New Oscillator for a wobble, New Value or New Keyframes, or a node the clip already has; the Nodes tab opens on the new node so you can set its speed and range. Fixed (keep keys) holds the value and ignores its keyframes without deleting them; Local value / keyframes switches back. While a node drives the setting or it is fixed, the icon is lit and a line under the row says so (Node · Source with Go to source, or Fixed · Source). More: Parameter sources.
Styles. Many effects are looks of one shared engine: the print, line, textile, pixel, lens and glitch patterns share one, the text and glyph looks another, the tracking overlays a third. Their card has a Style menu at the top, with the looks of the effect's own group first and the other groups under their names. A control you changed keeps its value and keyframes when the new look has the same control, also under another name (Halftone's Ink is Riso's Dark Ink), brought into the new look's range, also on a way back through a look where it happens to be the default. A control you left alone (still at the default of the look you set it in) opens at the new look's default. A control that does something else in the new look (Halftone's Scale is a cell size, CRT Screen's Mask Density a stripe width, Drift Lines' Drift a distance) starts at its default; Undo brings back the old value and keyframes. A control only the old look has keeps its value and keyframes for a switch back. A control a node drives stays driven. Edits to the node graph belong to the old look and are reset. The row under the menu names each of these changes that touches something you set.
Presets. Effects that come with presets have a Preset row under Style. A preset is a named starting point: it sets the controls of the card at once, in a single update, so the playing preview does not stall (it used to write each control on its own), and one undo takes it back. What belongs to your shot stays as it is: the screen colour of a key, a measured lens, where a figure stands, and quality settings. A control with keyframes keeps them, and the card says so. An effect saved by an earlier version, or one you changed in the Nodes tab, may lack some controls a preset sets; the card names them and offers Update node setup to bring the effect up to date. That also replaces your own changes in the Nodes tab; Undo brings them back. Each effect page shows its presets.
Your own effects. To reuse an effect you have set up, open the Nodes tab, click Effect presets, give it a name and click Save effect copy. Under Saved effects, Add copy adds it to the selected clip, in any project in this browser.
Particle Out (next to the effect list) adds a ready-made outro: Pixel Particle Disintegrate with keyframes that blow the picture away at the end of the clip.
Most effects are small node setups you can open and change. Open the Nodes tab and pick the clip in its source list: each effect is a folded card, and the › left of its title opens it. Changes apply to this one effect. Each effect page shows its setup under Node setup; how to add and connect nodes: Nodes basics.
The Video / Audio switch at the top of the Effects tab shows the clip's sound effects instead (volume, EQ, compressor and more). See Audio.
How effects are registered, rendered, cached and exported, and how their pages are made: Effect system. Their building blocks: Node Catalog. The preview and the export use the same effect render path.