A small, quiet video editor you can talk to.
Rust core · GPU-rendered · titles, looks, music and motion made in place · a story board · screen recording · an assistant that edits beside you

Install · Using it · Looks · Music and scenes · Story · Assistants

To splice film is to join two pieces of it: cut, line up, tape. Splice keeps editing that simple. CapCut is the inspiration and simplicity the rule: bring in videos, images and sound, layer them on a timeline, cut, play, export.

Why Splice

1. It stays out of the way. Media on the left, the picture in the middle, settings on the right, the timeline below. Everything is one click or one key, and every change is one undo step.
2. It makes what you would otherwise fetch. Titles in any installed font, colour cards, green screen, masks and motion; music written as a score and played with real instruments; animated diagrams drawn from a short description. No plug-ins, no second app.
3. It plans as well as cuts. A story board of beats, shots and reference pictures sits on the same timeline as the footage, and the screen recorder drops takes straight into the beat they are for.
4. Assistants work beside you. splice ctl lets Claude, or any program, read the project, edit it, compose its music, look at any frame and record the screen, while you keep working. A project is one file, autosaved and versioned.

Install

curl -fsSL https://raw.githubusercontent.com/ArchAstro/splice/main/install.sh | sh

This downloads the latest release for macOS 13+ (Apple Silicon or Intel), checks it against the published checksums, installs Splice.app into /Applications with the splice command in ~/.local/bin (the same program), the Claude Code skill in ~/.claude/skills/splice, and ffmpeg with Homebrew if it is missing. SPLICE_VERSION=v0.1.0, SPLICE_INSTALL_DIR, SPLICE_APP=0 (the command only), SPLICE_FFMPEG=0 and SPLICE_SKILL=0 change that.

You can also download splice-macos.dmg from the releases page and drag the app across. Until releases are signed with a Developer ID, an app downloaded in a browser needs a right-click → Open the first time; the installer does not.

To build from source instead (needs Rust 1.90+ and brew install ffmpeg):

git clone https://github.com/ArchAstro/splice && cd splice
make install       # builds splice into ~/.cargo/bin and links the skill
make run           # or run it straight from the checkout
make install-app   # Splice.app in /Applications

Using it

• Import: ⌘I, the Import button, or drop files from Finder anywhere on the window. Drop them on the timeline to place them where they land.
• Arrange: drag media from the bin onto the timeline. Drag clips to move them in time or between layers, and drag above the top layer to make a new one. Higher layers draw over lower ones. Clips snap to edges and the playhead; hold ⌥ to move freely.
• Trim: drag either end of a clip.
• Cut: S or ⌘B splits the selection at the playhead, or every clip under it if nothing is selected. ⌫ deletes, ⇧⌫ ripple-deletes (closes the gap), ⌘D duplicates.
• Play: Space plays and pauses. ← → step one frame, ⇧← ⇧→ (or J, L) one second. Click or drag the ruler to scrub.
• Layers: each track's gutter toggles visible / hidden and sound / muted (H and M act on the selection's tracks).
• Canvas: the first clip sets the canvas shape. The shape button cycles 16:9, 9:16, 1:1 and 4:5.
• Export: ⌘E (H.264 + AAC MP4), or ⇧⌘E for a fast draft.
• Everything else: ⌘/ opens the command menu, with every command and its key.

Titles and looks

• Text (⌘T, or the Text shelf): titles in any installed font, with size, bold, italic, alignment, colour, a box behind and a soft shadow. Type in the inspector, or double-click a title on the stage.
• Words come in one at a time: by word, letter or line, fading, rising, popping or typed; set it in the Text section.
• Captions (Edit → Add Captions from Speech, or the clip's Sound section): Splice hears what is said, on your Mac (whisper.cpp, brew install whisper-cpp; a 148 MB speech model downloads once), and lays captions over it, each word lighting up as it is said. Each caption is a title you can edit. .srt and .vtt files load too.
• Colour shelf: full-frame colours for backgrounds and title cards, a half-black tint, and light leaks that wash warm or cool light over a shot.
• Letterbox (the canvas inspector, with nothing selected): bars that frame the whole movie to 2.39, 2:1, 1.85 or 4:3.
• Inspector (⌘2), for the selected clip:
  • Place: drag a picture on the stage, or its corners to resize. It snaps to the centre lines. There's a nine-point grid, plus size, opacity and position sliders.
  • Keyframes: the ◆ beside size, opacity and position keys that value at the playhead; set another somewhere else and it glides between them (linear, smooth, ease in, ease out, or hold). Dragging a keyframed picture on the stage keys it where the playhead is. ⌥K keys place and size at once.
  • Transition: the way into a clip from the one before it: dissolve, dip to black or white, wipe or push four ways, or zoom, centred on the cut, with a length. A tab on the timeline marks each one. ⇧⌘T adds a dissolve at the nearest cut.
  • Animate: in and out with fade, slide (four ways), zoom or pop, with a length you choose. A slow zoom can run across the whole clip.
  • Colour: a look (warm, cool, vivid, muted, faded, film, teal & orange, black & white, noir) with exposure, contrast, saturation, warmth and tint over it. Use on every clip grades the whole movie the same.
  • Effects: blur, vignette, film grain, a handheld shake and a glitch, each a slider.
  • Background: fill the canvas behind a picture with a blurred, darkened copy of it: a phone video on a wide canvas.
  • Hide part: blur, pixelate or black out a box of the picture (a face, a screen, a number plate).
  • Speed: 0.25× to 4× (0.1× to 16× from the assistant), or backwards. A faster clip gets shorter and what follows on its track moves up; sound keeps its pitch. Freeze frame (⌥F) holds the frame at the playhead.
  • Green screen: key out green or blue, with strength, softness and fringe clean-up.
  • Crop: cut any edge away. The picture keeps its scale, and what remains stays where it was.
  • Mask: circle or box, with size, position, feather and invert.
  • Sound: volume.

The viewer and export share one renderer, so what you see is what you get. Titles are drawn once in Rust (cosmic-text) and that same picture is overlaid on export. Keys and masks are ffmpeg filters that the viewer's decoder runs too, and so is colour. Animation, keyframes and transitions are one set of expressions, evaluated for the viewer and printed into ffmpeg for export.

Scores and scenes

Two kinds of media Splice makes rather than imports. Each opens in its own editor (double-click it in the media panel or on the timeline, or use the New score / New scene tiles), and each re-renders when it changes, with every clip of it following.

• Score: music as notes. Instruments, tempo, meter and notes in beats, shown as a piano roll with one lane per instrument. Click to add a note, drag to move or lengthen it, ⌫ to delete. Each lane has mute, solo, an instrument picker covering the 128 General MIDI instruments plus a drum kit, and a little mixer: a Level fader in dB and a Pan. Shift-drag a fader for fine changes; double-click resets it. It plays with the timeline, so you hear it against the picture. Splice renders it with rustysynth and the GeneralUser GS SoundFont, which it downloads once (32 MB) and checks. The assistant can compose it from JSON (the same shape as Clapper's scores); Ask in the editor sends it what you have open.
• Scene: an animation or diagram described as JSON: layers of rects, ellipses, lines, SVG paths, text and groups, with keyframes, eases, springs, staggered entrances and exits, outlines that draw themselves, typed and counted text, gradients, soft shadows and a camera. Splice paints every frame itself, with tiny-skia for shapes and cosmic-text for words. It encodes to ProRes 4444 with a transparent background by default, so a scene overlays what is under it, and a 5 s scene renders in about a second. The editor shows the JSON with syntax colours (and a swatch by each colour) beside the picture. Edit opens the file in your text editor, and every save re-renders it.

Renders are cached by what they are made from, and kept in the project file so it still opens anywhere.

Symbols

A symbol is a piece of a movie kept for reuse in every project: an intro, a lower third, a logo sting, an end card. Select the clips and choose Make Symbol (⌥⌘K, in the Edit menu, or + on the Symbols shelf). Name it, and tick the titles each use can change. It goes into your symbols, and the clips become one clip on the timeline: a use of the symbol. Their layering, looks and motion stay as they were.

• Placeholders are what each use can change. When you make a symbol, its titles become placeholders ("Title", "Title 2"). In the symbol's own window, switch on Each use can change this in the inspector to make a colour, a picture or video, or a sound a placeholder too. Give two clips the same placeholder name and they change together. Renaming a placeholder keeps what uses filled in.
• Using one: the Symbols shelf shows each symbol with a poster and its length. Click it to add it at the playhead, or drag it onto the timeline. Select the use and fill in its placeholders, which the inspector shows first: type words (the picture follows as you type), pick a swatch or type a hex colour, or pick, import or drop media. Every use has its own fills, including one you duplicate. A use is named by its words, such as "Lower third · Grace Hopper".
• Changing one: Edit opens the symbol in its own window, an ordinary Splice project with a banner and a see-through stage. Changes reach other movies when you publish them with ⌘S. The status bar then says a newer version is there, and out-of-date uses are marked on the timeline. A use offers Update (or Update all), keeps what you filled in, and says beforehand if anything would be dropped. Undo brings it back.
• Other shapes: a 16:9 symbol in a 9:16 movie keeps its shape by default, rendered sharp at the movie's size. Fit this movie lays it out for the movie's own shape instead.
• Longer or shorter: drag the end of a use to make it run longer or shorter. Its hold stretches, so the entrance and exit keep their timing. Set the hold in the symbol's own window (Canvas inspector: Starts here, Ends here); without one, the whole symbol stretches evenly.
• Break apart (⌥⌘B) turns a use back into its clips, to edit them freely.
• Managing them: the ⋯ on a symbol's card has Edit, Rename, Duplicate, Show in Finder and Move to Trash. Symbols live in ~/Library/Application Support/Splice/Symbols, one .splice file each. Each symbol keeps its own identity, so renaming it in Finder doesn't disconnect its uses.
• A project keeps its own copy of every symbol it uses, with the media, so it still opens on a Mac without them. Keep in my symbols puts that copy back in your symbols. Renders of uses stay in the cache, not the project file.

Story and recording

Story (⌘3, or Edit / Story in the title bar) plans the movie before and while you cut it.

• Beats run end to end from the start of the timeline. Each one has a title, what happens, what to capture, and a length.
• The Story board shows the beats as cards, each with a frame of its footage or a "to capture" panel and a covered / partly / empty badge.
  • Double-click any text to type in it; Tab moves to the next field.
  • Drag cards to reorder them.
  • Drop media on a card to lay it into that beat.
• The timeline gets a story lane under the ruler. Each beat shows in its own colour, hatched where it still needs footage. Drag a beat's end to lengthen it.
• Footage belongs to the beat it starts in. Reordering, resizing or removing beats carries the footage along. Removing a beat never deletes footage.
• Reference shots: each beat can hold any number, each a picture of what a shot should look like, with a note.
  • Ways to add them:
    • drop image or video files from Finder on a card
    • paste a screenshot with ⌘V (⌃⇧⌘4 copies one)
    • grab the viewer's current frame
    • pick files with +
  • They show as a strip on the card; click one to see it large.
  • Until a beat has footage, its first reference stands in for the picture.
  • They are kept in the project file, out of the media panel.
• Cues (C) mark moments on the ruler, such as "VO starts" or "music lifts".
• Bible (the second page of Story view): the characters, places and things the movie keeps coming back to, and its look. Each has pictures (drop them on the card; the first is its face) and the words that must stay the same in every shot.
• Cast: each beat card shows who and what is in it as faces. Click + Cast to choose from the bible.
• Takes: footage tried for a beat, generated or shot. Each remembers how it was made (model, prompt, references). Click a take on the beat card to lay it in. A take still being generated pulses, and the story lane says so.
• Brief copies the chosen beat's brief, a prompt to start from. It carries the beat's story, framing, cast, look, length and shape. splice ctl story brief also writes out the references and the frames around the beat, for an assistant generating footage. Seedance through Higgsfield works well; see the skill.
• Shot list copies the plan as text.
• Keys: B adds a beat, C marks a cue.

Record (⇧⌘R, or the record button) captures the screen with macOS's own recorder, so there is no OBS and no extra install.

• You can record the entire screen or any one window, with the cursor and optional clicks and microphone.
• Recording the whole screen hides Splice. Click it in the Dock to stop.
• The take comes into the media panel. In Story view it goes into the chosen beat instead.
• The first recording asks for Screen Recording permission. It is granted to whatever launched Splice: the app, or your terminal.

Projects

A project is one .splice file: a SQLite database holding the imported media and every version of the timeline. Copy it anywhere and it opens with its media intact.

• Autosave: every change is written within two seconds. New projects start as ~/Movies/Splice/Untitled N.splice; ⌘S on one asks where to keep it.
• Versions: autosaves and saves (⌘S) are both kept in the file. ⇧⌘H lists them, and restoring one is an ordinary edit, so ⌘Z takes it back.
• Formats are versioned: the file records its format version and the project JSON its schema, and both have upgrade hooks.

Headless, for scripts:

splice --new film.splice a.mp4 b.png c.m4a   # media end to end
splice --info film.splice
splice --export film.splice film.mp4 [--draft]

Assistants

Other programs work in the open project through splice ctl while you edit, after Stet's stet ctl. The included skill (skill/splice/SKILL.md, installed with make install-skill) teaches Claude Code to use it.

Command	Does
splice ctl status / read	the project; every track and clip with ids and times
splice ctl frame [T] out.png	the picture at time T, drawn as export draws it
splice ctl import FILES [--at T]	brings media in, optionally onto the timeline
splice ctl add / move / trim / split / delete / duplicate / volume	timeline edits, each one undo step
splice ctl track, canvas, undo, redo	layers, canvas shape, history
splice ctl text, color, style, fonts	titles in system fonts, colour cards and tints
splice ctl look	position, size, opacity, animation, green screen, mask, crop, colour
splice ctl transition	dissolves, dips, wipes, pushes and zooms at cuts
splice ctl speed, freeze	faster, slower, backwards; hold a frame
splice ctl keyframe	animate position, size and opacity between moments
splice ctl captions	captions from speech (on this Mac) or a subtitle file
splice ctl zoom	zoom a screen recording in where it was clicked
splice ctl leak	light leaks over a shot
splice ctl score new / read / write / instruments	compose music: a score as JSON
splice ctl scene new / read / write / help	animations and diagrams, described as JSON
splice ctl scene sheet / frame / patch / add / remove / check	see a scene's motion as a contact sheet; edit layers by name; validate first
splice ctl open --media M	opens a score or scene in its editor
splice ctl seek, play, pause, select, command	the playhead, selection and any menu command
splice ctl save, versions, export FILE [--wait]	versions and export
splice ctl ui, click, hover, drag, scroll, key, type	operate the window as a person would, for checking the interface
splice ctl story read / add / set / move / remove / fill / list / shot, cue add / set / remove, `view edit	story`
splice ctl record sources / start / stop / status	record a screen, a window or a region, into a beat or the timeline
splice ctl wait --name Claude	connects an assistant and waits for your message
splice ctl say --text T	shows a line in the status bar

While an assistant waits, the title bar shows ● Claude; press ⇧⌘A (or click it) to send a message. Your playhead and selected clips travel with it, so "tighten this clip" means the one you selected. Each window listens on its own socket in ~/Library/Application Support/Splice/ctl/, and only your user can connect. With one window open, commands go to it; with several, name the project: splice ctl --project demo status, or set SPLICE_PROJECT once for a session.

Contributing

See CONTRIBUTING.md. Security reports go through SECURITY.md, not issues. Splice is MIT licensed.

Layout

Crate	Owns
crates/splice-core	timeline model and edits, undo, the .splice file, export plans. No platform code.
crates/splice-app	GPUI window, bin, viewer, timeline, ffmpeg decoding, playback, sound (cpal)

Decoding and export run ffmpeg as a child process. A bad file can't crash the editor, and codec support is whatever your ffmpeg has.