Mercato is a web based app platform (similar to an app store) that:

Guarantees your privacy by running your apps inside of a privacy sandbox - developers cannot see your data
Your data for all apps is available on all your devices by syncing your data through RemoteStorage
Your apps work on any device with a web browser
You own your data - you can view/export/delete any of your data that's stored inside RemoteStorage at any time.
Did we mention this is all free?

Seem too good to be true?

Mercato is based on a simple principle: an app cannot violate your privacy if it cannot send your data to the app developers or anyone else. So Mercato runs your apps inside of a privacy sandbox, where the apps cannot communicate to anywhere on the internet. The privacy sandbox works using modern web standards so it is available on any modern browser.

The tradeoff is that Mercato can't run some types of apps that require data to be sent over the internet. So you couldn't build a search engine or social network on Mercato. However, it's perfect for creative tools like document editors, spreadsheets, drawing apps, journals, todo apps, etc.

Getting started (all services are free)

A quick caveat: Mercato and much of the RemoteStorage ecosystem are considered to be in beta. We recommend using a tool like rs-backup to keep a copy of your data. (This is currently a developer command line tool, but we'd like to make it a more user friendly desktop or web app. Feel free to volunteer!)

1. Sign up for a RemoteStorage account

5apps.com is a free provider that has been around for a while, but if you'd like more options there's a great guide on RemoteStorage.io.

2. Connect to your RemoteStorage account

Mercato uses a token stored in your RemoteStorage to remember who you are, so to get started, connect to your RemoteStorage:

There's no additional setup needed for mercato - just sign in to your RS account

3. Start using apps

At any time (including before you create a mercato account) you can browse the list of all the apps available at: the app list

Why doesn't this cost more?

Storage of normal text data (eg things like documents) is fairly small compared to the size of video/songs/etc and is fairly cheap for developers. Your device runs the apps (rather than the Mercato server) so there's no need to pay for compute.