Android
Get the app.
Inchboost isn't on Google Play, so you install it straight from here. It takes about a minute, and you only do it once.
Installing in four steps
Tap download
Your browser may ask if you want to keep the file. Choose Download.
Open the file
Tap the finished download in your notifications, or find it in your Downloads folder.
Allow the install once
Android asks you to allow apps from this source. Tap Settings, switch on Allow from this source, then go back. You only need to do this the first time.
Tap install
That's it. Open Inchboost and pick your first photo.
Is this safe?
Android shows the same warning for every app that doesn't come from Google Play. Inchboost is signed by Canyon Tide Media LLC, asks for access to your photos only when you pick one, and never sends your photos anywhere. The editing happens on your phone.
On iPhone or a computer?
A browser version is on its way. It will run in Safari, Chrome and other modern browsers on iPhone, Mac and Windows, with the same promise as the app: everything happens on your own device and your photo is never uploaded.