Frequently asked questions.
What people usually ask before installing Apolo, and after.
Is Apolo free?
Yes. It's free software under the GPLv3: you can use, copy and change it, at work too. The code is on GitHub.
Does it upload my images anywhere?
No. Everything happens on your computer: your images never leave it.
The only thing Apolo does outside is ask GitHub, once a day, which version is the latest. It doesn't send your images, who you are, or how often you use it. You can turn it off in Settings.
Why does my system warn me the first time I open it?
Because Apolo isn't signed with an Apple or Microsoft certificate. On macOS, go to System Settings › Privacy & Security and click “Open Anyway”. On Windows, in SmartScreen, click “More info” and “Run anyway”.
Which formats does it read and write?
It writes WebP, AVIF, JPEG XL, JPEG (with MozJPEG), PNG (with OxiPNG) and QOI.
It reads those, plus HEIC (iPhone photos), TIFF, GIF, BMP and PNM.
Does it give the same result as the official tools?
Yes, byte for byte: cwebp, cjpeg (MozJPEG), oxipng, avifenc and cjxl are inside Apolo, with all their options. Apolo shows you the equivalent command so you can run it anywhere, and it's checked in every version.
What is the SSIMULACRA 2 score?
A measure of how visible the loss is, designed to match what a person sees. At 90 you can't tell them apart even flipping between both images; at 80, you can't tell them apart side by side; below 50, it shows.
With “Quality by score”, Apolo finds the lowest quality that reaches the score you ask for, photo by photo.
Does it work on an Intel Mac, Windows on ARM or Linux on ARM?
Yes. The macOS .dmg works on Apple silicon and Intel, and Windows and Linux have their own versions for x64 and ARM.
How much memory does it need?
With 24-megapixel photos it stays around 2 GB, even in batches of hundreds of photos: it fits a computer with 8 GB.
How does it update?
By itself: when there's a new version, Apolo tells you and installs it with one click. On Linux, with the repository, it updates with the rest of your system.
Can I use it from the terminal?
Yes, with the apolo command line, which takes the options of cwebp, cjpeg, oxipng, avifenc and cjxl, and converts whole folders with apolo lote.
Does it work with AI agents?
Yes. Apolo includes an MCP server for Claude, Cursor, VS Code and any agent that speaks it: it analyzes, optimizes, compares formats and converts folders on your computer, and it never overwrites or deletes anything.
Who makes Apolo?
Webcafeína, a web design and development studio.