This plugin adds indentation guides to empty lines.

It is recommended, but not required, to use it together with Yggdroot/indentLine.

This plugin requires Neovim 0.4.0 or higher. It makes use of Neovim only features so it will not work in Vim.

If you are using Neomvim 0.5, you should use the lua branch.
It is much faster and has real-time update support.
It will become the default once Neovim 0.5 is released.

indent-blankline uses the virtual text feature from Neovim to display indentation guides on empty lines.
Virtual text can currently only be added after the end of the line, so it is not possible to use this to display indentation guides on lines with text.

The indentation level is generated like Neovim would generate normal indentation.
If indentexpr is empty, it uses cindent().
If indentexpr is set to lisp, it uses lispindent().
If indentexpr is set to anything else, it uses that function.

The lines to indent and the level of indentation is computed asynchronously with an embedded read-only instance of Neovim.

This makes generation of indentation not affect normal editing. But it could be resource intensive.
indent-blankline needs to open buffers in read-only mode with autocommands, to set up the correct indentexpr. In most cases this should not cause issues, but if you have side effects defined for opening buffers, this might lead to undesired execution of those.

A possible solution for this would be to check if Neovim has a UI attached before running such side effects.

if len(nvim_list_uis())
    " your side effect code
endif

indent-blankline does not require the indentLine Plugin. But it is recommended to use the two together.

Almost all settings from indentLine will work seamlessly with indent-blankline as well without any setup.

Please see :help indent_blankline.txt

Screenshots are made together with indentLine