Backdrop 0.4.0

What's new: a lens library, and lenses you can make yourself

The Lenses pane in the Studio is now a library: search, favourites, categories, and a card for each lens with its description, author and any problems found with it. The menu bar's lens row follows the same list.

• Make your own lens. A lens is a folder with a lens.json and any pictures it uses. No code, so lenses are safe to share. Pin pictures, emoji, text and shapes to your eyes, nose, mouth, forehead, head top, chin or cheeks; switch things on with a smile, a blink, an open mouth or raised eyebrows; bob, pulse, spin, wiggle, float or drop them in; bulge or pinch parts of the face; emit rainbows, fire, hearts, sparkles, confetti or bubbles; tint the whole picture. Five examples are put in your Lenses folder the first time. The format is in docs/LENS_FORMAT.md.
• Add, open and reload. Studio › Lenses › ⋯ has Add Lens…, Open Lenses Folder and Reload. Backdrop also looks for changes whenever it comes to the front, and puts a lens on again if its files changed. A lens that can't be used is listed at the top of the pane with a Show in Finder button; one with a bad part just skips that part and tells you.
• Blink and smile join mouth-open and eyebrow-raise as things a lens can react to. While a face lens is on, the menu bar shows all four live readings.

Sturdier

• A shared lens can't hurt you. Lenses are checked before they are used: no symlinks (a stranger's lens can no longer point at a picture elsewhere on your Mac), caps on file size, picture size, number of pictures, layers, emitters, warps and emoji length, and a fixed particle budget. Pictures are only decoded when you put a lens on, so a big library no longer slows Backdrop down at launch.
• Face signals misfire less. Turning your head no longer reads as raised eyebrows, a squint in a smile isn't a blink, a wink isn't a blink, the "ee" in a word isn't a smile, and a held smile doesn't fade. Eyebrow and mouth readings re-settle after you look away.
• Backdrop Camera. The app now only replaces the camera extension with a newer one, takes its installed state from macOS, and says when macOS wants a restart to finish. If macOS hasn't started the camera after an update, the menu bar says so and offers Restart Backdrop.
• Video order and restarts. Frames can no longer go out of order when a background is switched off while a cutout is in flight, and video and live-window backgrounds resume after the camera is turned off and on again (they used to stay frozen).
• Smaller fixes. Favourites survive a typo in lens.json, JSON errors name the line and column, lens names that collide no longer share an ID, and a lens with text shows an un-mirrored preview so the words read the right way round.

Install

1. Unzip it and drag Backdrop.app into Applications. It has to live there for macOS to accept its camera extension.
2. Open it. Click the menu bar icon, then Set Up Backdrop Camera, and approve it in System Settings › General › Login Items & Extensions › Camera Extensions.
3. Turn the camera on, then choose Backdrop Camera in your video app.

Upgrading: replace the app in Applications and open it. It updates its own camera extension when it starts. If another app (Discord, a browser, FaceTime) is using the camera at that moment, macOS can leave Backdrop Camera missing from the list afterwards. Quit those apps and restart Backdrop; if it is still missing, restart your Mac.

Requires macOS 15.1 or later on Apple silicon. AI backgrounds need Apple Intelligence.

Verify

Signed with a Developer ID certificate and notarized by Apple. To check the download:

shasum -a 256 -c Backdrop-0.4.0.zip.sha256

Early release

Developed and tested on a single Apple silicon Mac running macOS 27. The engine has automated tests, but the virtual camera and the lenses have had limited real-world testing, so expect rough edges. In particular:

• Face lenses were built and tested against drawn faces, not recorded real ones. The face readings are better reasoned than in 0.3.0, but where the crown, ears and hat sit, and how far you have to open your mouth, raise your eyebrows or smile, may still need tuning.
• The new Lenses library and the missing-camera notice have not been checked on more than one Mac.
• There's no Intel build, and no hand tracking yet.
• The camera is switched on and off by hand (menu bar or ⌃⌥B). It doesn't start by itself when another app opens Backdrop Camera.
• Backdrop Camera deliberately advertises 60 fps so macOS doesn't layer its own Background effect over the result. If that effect is on for Backdrop's own camera input, the app warns you.

Bug reports are welcome as issues.