GitHub Codespaces is a new online development environment launched and hosted by Github and its powered by Visual Studio Code. It includes everything that you need for a development environment, including a text editor, syntax highlighting, autocomplete, debugging tools, etc. It helps you to develop in the cloud instead of locally, thus you need not have to have a local development environment.
As of now, the Github Codespaces will be available to a small group of Github Users, but over time more users will have access to it based on how the best tests go on. It will be free of cost as of now but it might be they will change it once it gains popularity.
According to Github:
Each developer can create one or more codespace for any public repository, or for any private repository owned by their user account. During the beta, private repositories owned by organizations or any repositories owned by an organization that requires SAML single sign-on are not supported. Each codespace you create is only available to you. No one else can work in your codespace.
Each codespace is associated with a specific branch of a repository. You can create more than one codespace per-repository or even per branch. However, each user account has a five-codespace limit. If you've reached the limit and want to create a new codespace, you must delete a codespace first. For more information, see "Deleting a codespace."
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