An After Effects expressions library you apply with a click
An After Effects expressions library is a set of ready-made expressions you apply to a selected property instead of typing code. mouzeclick has three: 25 recommended expressions in the workspace Library, 42 text and motion expressions in Type studio (both Windows only), and mouzeexpr's 24 expressions with settings and Bake, which runs on Windows and Mac.
- Library: 25 recommended expressions in four groups (Motion, Loops, Text, Utility), plus your own
- Type studio: 20 text and 22 motion expressions, with settings you can change
- mouzeexpr: 24 expressions; Apply, Update, Remove and Bake to keyframes; Windows and Mac
- Every one goes on the property you select; no typing
- The workspaces are Windows only; mouzeexpr, mouzerun and mouzekit run on Windows and Mac
What is an After Effects expressions library, and does After Effects have one?
It is a list of working expressions you can apply by name, and After Effects does not really have one. It has the expression language, a menu of functions, and no built-in list of ready recipes.
The built-in way to add an expression:
- Twirl open the layer and find the property, such as Position or Rotation.
- Alt-click its stopwatch (Option-click on a Mac). An expression field opens on the timeline.
- Type the expression, or use the small arrow beside the field, the expression language menu, to insert a function.
- Click outside the field. If the code has a problem, After Effects shows a warning bar with the error.
The language menu gives you function names such as wiggle() and loopOut(), not finished recipes with sensible numbers. So most animators keep a text file of snippets, or save an animated property with Animation › Save Animation Preset, which stores its expression in an .ffx file. Both work. Neither shows you what the expression does before you use it, and neither has settings you can change without editing code. (If you are unsure where expressions end and scripts begin, see plugin vs script vs extension.)
What do wiggle, loopOut and time do in plain words?
wiggle adds random movement, loopOut repeats your keyframes, and time makes a value grow every second. Most animators learn these three first.
wiggle(5, 30)moves the value randomly 5 times a second, up to 30 units away from where you keyed it: pixels on Position, degrees on Rotation, percent on Opacity. Your own keyframes still apply underneath.loopOut("cycle")plays your keyframes, then repeats them for the rest of the layer. Swap the word:"pingpong"plays forward then backward,"offset"repeats and adds the change each time (a staircase),"continue"keeps going at the speed of the last keyframe.loopIn()does the same before the first key. Both need at least two keyframes.time * 90on Rotation turns the layer 90 degrees every second, forever, without a single keyframe.
Two more worth knowing: linear(time, 0, 2, 0, 100) maps one range onto another (here 0 to 100 over the first two seconds), and thisComp.layer("Null 1").transform.position makes one property follow another layer. That last one breaks the moment someone renames “Null 1”.
What's in mouzeclick's After Effects expressions library?
The main one is in the Library section of the mouzeclick workspace for After Effects: 25 recommended expressions with plain descriptions, plus your own. Click a card to apply it to the selected property; you can also copy it or save it.
| Group | Expressions |
|---|---|
| Motion (7) | Wiggle, Wiggle X only, Inertial bounce, Overshoot, Follow the layer above, Constant spin, Ease between two values |
| Loops (5) | Loop (cycle), Loop (ping-pong), Loop (offset), Keep moving, Loop before and after |
| Text (4) | Typewriter, Count up, Timecode readout, Layer name |
| Utility (9) | Fade in and out, Clamp, Uniform scale, Fit to comp width, Anchor at bottom centre, Stop-motion, Random, but stable, Point at a layer, Fade with distance |
The Loops group puts loopOut and loopIn behind plain names, so you never type the quotes. Follow the layer above copies the position of the layer above with a five-frame delay; stack several layers for a trail. Random, but stable gives each layer its own random number that never flickers, which is what you want for a scatter of shapes.
Your expressions sit next to these: save one you wrote and it is a click away in every project. Three more tools live in the Toolbox: Elastic and Bounce add an elastic or an inertial bounce expression to keyed properties, and Smart bake swaps expressions for fewer keyframes within a tolerance you set.
Which text and motion expressions are in Type studio?
Type studio, next to its text animation presets, has 42 expressions: 20 for text and 22 for motion, each with settings you can change.
- Text (20): Typewriter, Typewriter and cursor, Word by word, Text cycle, Random reveal, Blinking text, Digital noise, Ellipsis loader, Slot machine, Decode, and counters and clocks: Number counter, Currency counter, Percentage counter, Decimal counter, Bounce counter, Countdown timer, Simple countdown, Stopwatch, Date display, Time display.
- Motion (22): ten wiggles (Wiggle, Smooth, Decay, X-axis, Y-axis, Loopable, Snapping, Separate XY, Jumpy, Noise), then Shake, Jitter, Drift, Random jump, Friction slide, Air drag, Wind sway, Handheld realistic, Camera drift, Pendulum rotation, Swing, Inertia.
Text expressions go on a text layer's Source Text; motion expressions go on a property such as Position, Rotation or Scale. Hover any of them and it previews beside the pointer before you double-click. The rest of Type studio's 159 presets are on the After Effects text animation presets page; Shake and Handheld realistic are covered with the camera shake presets.
How does mouzeexpr apply, update and bake an expression?
mouzeexpr is a small After Effects panel, one of the 22 mouzeclick extensions, with 24 ready-made expressions that each have settings. It runs on Windows and Mac.
- Motion: Inertial bounce, Elastic, Oscillate, Drift, Squash and stretch, Time spin, Loop.
- Text and numbers: Countdown or clock, Number format, Text from list, Typewriter.
- Links: Delay follow, Stick to, Look at, Path follow, Box to text.
- Also: Random hold, Value from marker, Blink, Auto-fade, Snap to grid, Clamp, Keep stroke width, Parent-free scale.
The workflow is four buttons. Select properties and press Apply: the expression goes on every selected property it fits. Update changes it in place after you move a setting. Remove takes it off along with its controls. Bake turns it into keyframes over the work area, either one key a frame or fewer keys within a tolerance.
Alt-click Apply also replaces expressions you wrote yourself; a plain click leaves them alone. Search and favourites keep the list short. The built-in equivalent of Bake is Animation › Keyframe Assistant › Convert Expression to Keyframes, which always writes a key on every frame.
How do you save your own expressions so you can reuse them?
In After Effects alone, save the property as an animation preset or keep a snippets file. With mouzeclick, save it in the workspace Library or make it a one-click button.
- Animation preset. Select the property with the expression and choose Animation › Save Animation Preset. It lands in Effects & Presets as an .ffx file.
- Your expressions (Windows). In the workspace Library, save an expression you wrote and apply it later with one click, next to the 25 recommended ones.
- mouzerun buttons (Windows and Mac). mouzerun makes a panel of your own buttons. One kind of button puts an expression on the selected properties; the others run a script, apply an animation preset, run a menu command or set an ease. It starts with six example buttons, including Wiggle and Loop, and your buttons are saved in its folder, so updates keep them.
- The Tool wheel. On Windows and Mac, the After Effects Tool wheel has a Loop, ping-pong, wiggle group one flick away on F10.
I keep loops and links as buttons and everything else in the Library. Buttons are for the three expressions you use every hour; the Library is for the twenty you use every month.
Why does an After Effects expression show an error?
Usually because it points at something that changed: a renamed layer, a different language, or a different expression engine.
- A layer or effect was renamed.
thisComp.layer("Logo")fails once Logo is called Logo 2. Rename it back, or relink with the pick whip. - Another language of After Effects. Expressions that call an effect by its English name can break in a German or Japanese install. mouzekit's rigs are written to work in any language of After Effects.
- The expression engine. Projects can use the JavaScript engine or the older Legacy ExtendScript one, set in File › Project Settings. A snippet written for one can fail in the other.
- The wrong kind of property. Position expects two or three numbers, Opacity expects one. An expression that returns the wrong shape errors out.
- Nothing loops.
loopOut()repeats keyframes, so the property needs at least two. - It works but previews crawl. Expressions are worked out every frame. Bake the finished ones to keyframes with mouzeexpr, Smart bake or Convert Expression to Keyframes.
Press EE (E twice, quickly) with layers selected to show every property that has an expression, which is the quickest way to find the one that broke.
What other tools keep expressions one click away?
Two well-known ones, both for After Effects only and both paid once. Facts were checked on the makers' pages on 31 October 2026.
| Tool | What it does with expressions | Price shown | Latest version |
|---|---|---|---|
| KBar (aescripts) | Toolbar buttons for expressions, scripts, effects, presets, menu commands and shell commands; up to 4 toolbars | $39.99 | 3.1.5, 19 Jan 2026 |
| Motion Tools Pro (Motion Design School) | A grid panel of 30+ scripts and widgets with an expression editor | $40 | 2.1.2, 18 Jun 2026 |
| mouzeclick | Library, Type studio and mouzeexpr expressions, mouzerun buttons | One plan: $25 a month, $249 a year or $499 lifetime | 0.58.40, 25 Oct 2026 |
Where they are the better pick: you want one focused tool, paid once, and you mostly write your own code. KBar in particular is a standard other scripts export to, Flow among them. See the KBar comparison for the full picture.
Where mouzeclick fits: you want ready expressions with settings and Bake, the same tools on Windows and Mac through mouzeexpr and mouzerun, and, on Windows, the whole workspace around them. The all-in-one After Effects extension guide shows the rest.
Try the expressions library free for 3 days, no card. One plan with everything included, $25 a month, or $249 for a year.
Questions people ask
How do I add an expression in After Effects?
Alt-click the stopwatch next to the property (Option-click on a Mac). An expression field opens on the timeline; type or paste the code and click outside it. To remove it, Alt-click the stopwatch again. With mouzeclick, select the property and click an expression in the Library, Type studio or mouzeexpr instead of typing.What is the difference between loopOut and loopIn?
loopOut repeats your keyframes after the last one, for the rest of the layer. loopIn repeats them before the first one, back to the layer's start. Both take the same types: cycle, pingpong, offset and continue. In the mouzeclick Library, Loop before and after does both at once.Do expressions slow down After Effects?
They can. An expression is worked out on every frame, so dozens of wiggles and links on many layers make previews slower. Once an animation is approved, bake it: mouzeexpr's Bake writes keys over the work area (every frame, or fewer within a tolerance), Smart bake in the workspace Toolbox does the same, and After Effects has Convert Expression to Keyframes.Can I use these expressions on a Mac?
Partly. The workspace Library and Type studio are Windows only, because the mouzeclick workspaces are not in the Mac app. mouzeexpr's 24 expressions, mouzerun's buttons and mouzekit's rigs all run on Windows and Mac. Whatever you apply is stored in the project as an ordinary expression, the same as one you typed.Can I edit an expression after applying it?
Yes. Press EE to show every property with an expression, then click the code and edit it like any expression you typed. In mouzeexpr, change a setting and press Update to rewrite it in place. If you edited the code by hand, a plain Apply leaves your version alone; Alt-click Apply replaces it.How do I make an expression that counts up a number?
On Windows, apply Number counter, Currency counter or Percentage counter from Type studio to a text layer's Source Text and set the values in its settings. Count up in the Library counts from 0 to 1,000 over 3 seconds with thousands separators. On Windows or Mac, mouzeexpr has Countdown or clock and Number format. By hand it isMath.round(linear(time, 0, 2, 0, 1000)) on Source Text.Is the expressions library included in the mouzeclick price?
Yes. mouzeclick is one plan with everything in it: $25 a month, $249 a year or $499 for a lifetime key, including every extension and, on Windows, both workspaces. Try it free for 3 days with no card. A creator or friend code takes 10% off a new customer's first 30-day or 1-year payment.Can expressions ease between two values?
Yes.ease(time, 0, 1, 0, 100) moves from 0 to 100 over the first second with a soft start and stop; linear() does it at a constant speed. The Library's Ease between two values applies that without typing. For curves beyond a simple ease, use keyframes and a saved curve from Easing lab instead; see After Effects easing presets.Sources
Checked on 2026-10-31. Prices and features change: each link goes to the maker's own page.