Dinky: A Free Mac App To Compress Images, Videos & PDFs Locally
The median desktop home page brings about 1,054 KB of images, according to the HTTP Archive Web Almanac. That’s before you count video or PDF assets. If you publish anything on the web, compression isn’t optional anymore. It’s just part of the job.
Dinky is a small macOS app that handles all three formats in one place. Drop files in. Smaller files come back. There’s no browser tab, no upload step, no account.
In this blogpost, we cover what Dinky does, how it stacks up against ImageOptim and Optimage, and the quieter automation features most reviews miss. We’ll also flag what to know before you install it.
Key Takeaways
- Dinky compresses images, videos, and PDFs locally on macOS 15 or later, free under MIT license with no paid tier.
- It outputs to WebP and AVIF, which together hit roughly 95% browser support based on caniuse data cited by SpeedVitals (September 2025).
- Watch Folders, Apple Shortcuts, and a built-in CLI turn it into a small automation engine, not just a drag-and-drop utility.
What is Dinky and who built it?
Dinky is a free open-source Mac utility built by Derek Castelli, a freelance Webflow and Figma designer. According to the project’s official site, version 2.0 added video and PDF support to what was previously an image-only tool. The whole app weighs about 33 MB installed. That’s tiny for a tool covering three file types.
Castelli built Dinky to handle his own client work. Compressing site images was a daily chore, and existing tools either cost money or skipped video and PDFs entirely. The app is written in Swift and SwiftUI, with no Electron, no web view, and no third-party UI framework.
The full source code lives on GitHub under an MIT license. You can audit it, fork it, or build it yourself.
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How does Dinky handle images, videos, and PDFs?
Dinky compresses all three formats from one drop zone. Image inputs include JPG, PNG, WebP, AVIF, HEIC, TIFF, and BMP. Outputs cover WebP, AVIF, lossless PNG, and HEIC. According to the project README, image work runs through cwebp, avifenc, and oxipng encoders bundled into the app itself.
Images
There’s an “Auto” mode that picks WebP or AVIF per file. That helps when batches mix product photos with UI screenshots, since the optimal format differs by content.
Videos
Video compression uses Apple’s AVFoundation framework with H.264 or HEVC encoders. You pick a quality preset, drop your file, and let it run.
PDFs
PDFs offer three modes: flatten for aggressive size reduction, preserve text and links, or hit a target size. An optional OCR pass using Apple’s Vision framework runs first when you need scanned documents to stay searchable.
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Why does file compression still matter in 2026?
Format choice does most of the heavy lifting. The 2024 HTTP Archive Web Almanac found WebP encodes at a median of 1.3 bits per pixel, versus 2.0 for JPG. That’s roughly a 35% reduction at the same quality level. AVIF lands at 1.4 bits per pixel, with stronger results on photos. Modern formats matter more than quality slider position.
So why are sites still slow? Most compression coverage frames bloat as a developer problem. It isn’t. The bottleneck is usually whoever’s exporting from Figma, Lightroom, or a screenshot tool. Those people rarely have a one-click way to convert formats on export. Watch Folders close exactly that gap.
Did You Know: WebP encodes at a median of 1.3 bits per pixel and AVIF at 1.4, compared to 2.0 for JPG, according to the HTTP Archive Web Almanac media chapter. That gap is where the real bandwidth savings live, more than quality slider tweaks ever deliver.
Dinky vs ImageOptim, Optimage, and Compresto
These four apps occupy different niches. ImageOptim is free and lossless-by-default, but image-only. Optimage costs $15 and focuses on visually lossless image work. Compresto has a free tier covering video, image, and PDF, with paid upgrades. Dinky is the only one that’s free, open source, and covers all three formats, based on the developers’ own product pages.
Where Dinky stands out
Three things, in our experience. The format set is tight and web-focused. Watch Folders fit real export workflows. The CLI ships for anyone who wants scripting access.
Where it falls short
For pure lossless PNG work, ImageOptim’s MozJPEG and Zopfli pipeline still squeezes out a few extra bytes. And if you need cross-platform tooling, Dinky won’t help. It’s macOS only, with no Windows or Linux port planned per the developer’s FAQ.
What automation features set Dinky apart?
Automation is where Dinky quietly outclasses most peers. Watch Folders auto-compress any file dropped into a chosen path. Apple Shortcuts integration lets you chain compression into bigger workflows. Pro users can build a local CLI from the repo and run dinky compress --json or dinky serve on loopback, per the official documentation.
The CLI nobody talks about
The loopback server is the part most reviews skip entirely. Run dinky serve on 127.0.0.1, and any local script, or even an AI agent like Claude Code, can hit it for compression jobs without touching the network. Small detail, but a real foothold for local automation pipelines.
Watch Folders in real workflows
Point a Watch Folder at your Figma export directory, your Lightroom output, or your screenshot folder. Files shrink as soon as they land. Set it once, and it runs forever.
Also read: Where to Find System Preferences on Mac? It’s here
Installation notes and Gatekeeper
Two practical limits matter before you install. Dinky needs macOS 15 Sequoia or later, so older Macs running Big Sur or Monterey are out. The app isn’t notarized, which means Gatekeeper will block first launch. Per the official FAQ, App Store sandboxing would break how Dinky shells out to its compression engines.
You can still run it. Open System Settings, scroll to Privacy & Security, then click “Open Anyway.” That’s all it takes.
If you’re cautious about unsigned apps, the source code is on GitHub. You can build it yourself or inspect the Homebrew cask first. Install via Homebrew with brew tap heyderekj/dinky https://github.com/heyderekj/dinky, then brew install --cask dinky.
Frequently asked questions
Yes. Per the developer’s FAQ at dinkyfiles.com, Dinky is free under an MIT open-source license. There’s no trial, no watermark, and no premium tier. The full source is on GitHub, so you can build it yourself if you’d rather not trust a binary download.
No. Everything runs locally on your Mac, according to the project’s official site. There’s no server, no sign-in, no cloud step at all. Dinky also strips EXIF, GPS, and camera metadata on the way out, which matters for screenshots and photos shared publicly.
Dinky needs macOS 15 Sequoia or later. On macOS 26 Tahoe you get the full liquid glass interface. On Sequoia it falls back to a frosted material look. Older macOS versions, including Ventura and Monterey, aren’t supported, so Intel Macs running them are out.
Both work for almost every visitor. WebP carries roughly 95.29% browser support, and AVIF around 93.8%, per caniuse data cited by SpeedVitals in September 2025. AVIF compresses smaller on photos. WebP decodes faster. For most web work, AVIF with a WebP fallback is the safe pick.
Final thoughts
Dinky doesn’t try to do too much. It takes one annoying job, making files smaller, and strips out the friction. Covering images, videos, and PDFs in a single free app is genuinely uncommon. Being open source on top of that is rarer still.
If your work involves prepping web assets, exporting from Figma, or shrinking PDFs before email, it’s worth installing. Set up a Watch Folder on your most-used export path. Try the ⌘⇧V clipboard hotkey for screenshots. See if it earns its place in your dock.
The download lives at dinkyfiles.com. Source is on GitHub. Costs nothing, and takes about a minute to set up. Whether you keep it depends on whether your workflow has the gaps Dinky was built to fill.
