It is not possible to use Overleaf offline as all compilations are run on our servers, but Overleaf v2 provides great new ways of working offline while syncing your edits to your Overleaf projects.
You can use any plain text editor to edit your projects locally, and you can download a free installation of LaTeX to compile your projects locally as well. You can see some options for installing LaTeX here: https://www.latex-project.org/get/ . To ensure you can run all of the packages of Overleaf "out-of-the-box", you can download the TeXLive distribution, and you can compile with Latexmk to compile everything in one go (see this article for more information on how Overleaf compiles your projects).
Overleaf v2 introduces an automatic two-way sync between Overleaf and Dropbox. Any changes to your project in Overleaf will automatically sync to your Dropbox folder on your computer, and any changes you make locally in Dropbox will appear in your project online.
From listening to user feedback, we understand how important it is to be able to seamlessly transition between working offline in your favourite editor to working online on Overleaf with your collaborators. Overleaf v1 only supported a one-way sync to Dropbox, where you could manually save your project to Dropbox with one click. This wasn't enough to take your work offline and then back online easily, and had a number of other limitations. With the much improved Dropbox sync in Overleaf v2 you should be able to work on your projects whenever you want, wherever you are, however you like.
Overleaf v2 offers direct sync to GitHub. While it is possible to sync an Overleaf v1 project with GitHub, it required setting up git remotes and manually keeping them in sync. We found that most people used Overleaf v1’s git support in conjunction with another git hosting service, most frequently GitHub, so we believe this will be an improvement for many users.
In order to use the GitHub sync in v2, users will need to have a GitHub account. A free Github account allows you to create public or private repositories.
If you work with git locally, it is still possible to use the Overleaf git bridge on v2. The integration lets you git clone, push and pull changes between the online Overleaf v2 editor, and your local offline git repository. You can find out more details in this blog post.
The git integration in Overleaf v1 was a free feature during its long beta period, and we will continue to offer it for free to all users whose accounts were created on Overleaf v1. For users who signed up after Overleaf v2 was out of beta, GitHub sync and direct git access will be available on our paid plans, like on ShareLaTeX. As with many other v2 features, this means that the owner of the project will need a paid subscription in order to connect their project with GitHub or enable direct git access, but their collaborators can use the integration with free accounts.