Nvim :help pages, generated from source using the tree-sitter-vimdoc parser.

Development of Nvim dev
This reference describes design constraints and guidelines, for developing Nvim applications or Nvim itself. Architecture and internal concepts are covered in src/nvim/
Nvim is free and open source. Everybody is encouraged to contribute.

Design goals design-goals

Most important things come first (roughly). Some items conflict; this is intentional. A balance must be found.

NVIM IS... IMPROVED design-improved

The Neo bits of Nvim should make it a better Vim, without becoming a completely different editor.
In matters of taste, prefer Vim/Unix tradition. If there is no relevant Vim/Unix tradition, consider the "common case".
There is no limit to the features that can be added. Select new features based on (1) what users ask for, (2) how much effort it takes to implement and (3) someone actually implementing it.
Backwards compatibility is a feature. The RPC API in particular should never break.

NVIM IS... WELL DOCUMENTED design-documented

A feature that isn't documented is a useless feature. A patch for a new feature must include the documentation.
Documentation should be comprehensive and understandable. Use examples.
Don't make the text unnecessarily long. Less documentation means that an item is easier to find.

NVIM IS... FAST AND SMALL design-speed-size

Keep Nvim small and fast. This directly affects versatility and usability.
Computers are becoming faster and bigger each year. Vim can grow too, but no faster than computers are growing. Keep Vim usable on older systems.
Many users start Vim from a shell very often. Startup time must be short.
Commands must work efficiently. The time they consume must be as small as possible. Useful commands may take longer.
Don't forget that some people use Vim over a slow connection. Minimize the communication overhead.
Vim is a component among other components. Don't turn it into a massive application, but have it work well together with other programs ("composability").

NVIM IS... MAINTAINABLE design-maintain

The source code should not become a mess. It should be reliable code.
Use comments in a useful way! Quoting the function name and argument names is NOT useful. Do explain what they are for.
Porting to another platform should be made easy, without having to change too much platform-independent code.
Use the object-oriented spirit: Put data and code together. Minimize the knowledge spread to other parts of the code.

NVIM IS... NOT design-not

Nvim is not an operating system; instead it should be composed with other tools or hosted as a component. Marvim once said: "Unlike Emacs, Nvim does not include the kitchen sink... but it's good for plumbing."

Developer guidelines dev-guidelines

PROVIDERS dev-provider

A primary goal of Nvim is to allow extension of the editor without special knowledge in the core. Some core functions are delegated to "providers" implemented as external scripts.
1. In the Vim source code, clipboard logic accounts for more than 1k lines of C source code (ui.c), to perform two tasks that are now accomplished with shell commands such as xclip or pbcopy/pbpaste.
2. Python scripting support: Vim has three files dedicated to embedding the Python interpreter: if_python.c, if_python3.c and if_py_both.h. Together these files sum about 9.5k lines of C source code. In contrast, Nvim Python scripting is performed by an external host process implemented in ~2k lines of Python.
The provider framework invokes Vimscript from C. It is composed of two functions in eval.c:
eval_call_provider({name}, {method}, {arguments}, {discard}): Calls provider#{name}#Call with {method} and {arguments}. If {discard} is true, any value returned by the provider will be discarded and empty value will be returned.
eval_has_provider({name}): Checks the g:loaded_{name}_provider variable which must be set to 2 by the provider script to indicate that it is "enabled and working". Called by has() to check if features are available.
For example, the Python provider is implemented by the "autoload/provider/python.vim" script, which sets g:loaded_python_provider to 2 only if a valid external Python host is found. Then has("python") reflects whether Python support is working.
provider-reload Sometimes a GUI or other application may want to force a provider to "reload". To reload a provider, undefine its "loaded" flag, then use :runtime to reload it:
:unlet g:loaded_clipboard_provider
:runtime autoload/provider/clipboard.vim


"Just say it". Avoid mushy, colloquial phrasing in all documentation (docstrings, user manual, website materials, newsletters, …). Don't mince words. Personality and flavor, used sparingly, are welcome--but in general, optimize for the reader's time and energy: be "precise yet concise".
Prefer the active voice: "Foo does X", not "X is done by Foo".
"The words you choose are an essential part of the user experience."
"...without being overly colloquial or frivolous."
Write docstrings (as opposed to inline comments) with present tense ("Gets"), not imperative ("Get"). This tends to reduce ambiguity and improve clarity by describing "What" instead of "How".
/// Gets a highlight definition.
/// Get a highlight definition.
Avoid starting docstrings with "The" or "A" unless needed to avoid ambiguity. This is a visual aid and reduces noise.
/// @param dirname Path fragment before `pend`
/// @param dirname The path fragment before `pend`
Vim differences:
Do not prefix help tags with "nvim-". Use vim_diff.txt to catalog differences from Vim; no other distinction is necessary.
If a Vim feature is removed, delete its help section and move its tag to vim_diff.txt.
Mention deprecated features in deprecated.txt and delete their old doc.
Use consistent language.
"terminal" in a help tag always means "the embedded terminal emulator", not "the user host terminal".
Use "tui-" to prefix help tags related to the host terminal, and "TUI" in prose if possible.
Rough guidelines on where Lua documentation should end up:
Nvim API functions vim.api.nvim_* should be in api.txt.
If the module is big and not relevant to generic and lower-level Lua functionality, then it's a strong candidate for separation. Example: treesitter.txt
Otherwise, add them to lua.txt
Documentation format
For Nvim-owned docs, use the following strict subset of "vimdoc" to ensure the help doc renders nicely in other formats (such as HTML: ).
Strict "vimdoc" subset:
Use lists (like this!) prefixed with "-" or "•", for adjacent lines that you don't want to auto-wrap. Lists are always rendered with "flow" layout (soft-wrapped) instead of preformatted (hard-wrapped) layout common in legacy :help docs.
Limitation: currently the parser does not understand numbered listitems, so use a bullet symbol (- or •) before numbered items, e.g. "• 1." instead of "1.".
Separate blocks (paragraphs) of content by a blank line.
Do not use indentation in random places—that prevents the page from using "flow" layout. If you need a preformatted section, put it in a help-codeblock starting with ">".
Parameters and fields are documented as {foo}.
Optional parameters and fields are documented as {foo}?.
C docstrings
Nvim API documentation lives in the source code, as docstrings (doc comments) on the function definitions. The api :help is generated from the docstrings defined in src/nvim/api/*.c.
Docstring format:
Lines start with ///
Special tokens start with @ followed by the token name: @note, @param, @return
Markdown is supported.
Tags are written as [tag]().
References are written as [tag]
Use`` for code samples. Code samples can be annotated as vim or lua
Example: the help for nvim_open_win() is generated from a docstring defined in src/nvim/api/win_config.c like this:
/// Opens a new window.
/// ...
/// Example (Lua): window-relative float
/// ```lua
/// vim.api.nvim_open_win(0, false, {
///   relative='win',
///   row=3,
///   col=3,
///   width=12,
///   height=3,
/// })
/// ```
/// @param buffer Buffer to display
/// @param enter  Enter the window
/// @param config Map defining the window configuration. Keys:
///   - relative: Sets the window layout, relative to:
///      - "editor" The global editor grid.
///      - "win"    Window given by the `win` field.
///      - "cursor" Cursor position in current window.
/// ...
/// @param[out] err Error details, if any
/// @return Window handle, or 0 on error
Lua docstrings
dev-lua-doc Lua documentation lives in the source code, as docstrings on the function definitions. The lua-vim :help is generated from the docstrings.
Docstring format:
Markdown is supported.
Tags are written as [tag]().
References are written as [tag]
Use`` for code samples. Code samples can be annotated as vim or lua
Use @nodoc to prevent documentation generation.
Use @inlinedoc to inline @class blocks into @param blocks. E.g.
--- Object with fields:
--- @class myOpts
--- @inlinedoc
--- Documentation for some field
--- @field somefield? integer
--- @param opts? myOpts
function foo(opts)
Will be rendered as:
      - {opts}? (table) Object with the fields:
                - {somefield}? (integer) Documentation
                  for some field
Files which has @meta are only used for typing and documentation.
Example: the help for vim.paste() is generated from a docstring decorating vim.paste in runtime/lua/vim/_editor.lua like this:
--- Paste handler, invoked by |nvim_paste()| when a conforming UI
--- (such as the |TUI|) pastes text into the editor.
--- Example: To remove ANSI color codes when pasting:
--- ```lua
--- vim.paste = (function()
---   local overridden = vim.paste
---   ...
--- end)()
--- ```
--- @see |paste|
--- @param lines  ...
--- @param phase  ...
--- @returns false if client should cancel the paste.


See also dev-naming.
Keep the core Lua modules lua-stdlib simple. Avoid elaborate OOP or pseudo-OOP designs. Plugin authors just want functions to call, not a big, fancy inheritance hierarchy.
Avoid requiring or returning special objects in the Nvim stdlib. Plain tables or values are easier to serialize, easier to construct from literals, easier to inspect and print, and inherently compatible with all Lua plugins. (This guideline doesn't apply to opaque, non-data objects like vim.cmd.)
stdlib functions should follow these common patterns:
accept iterable instead of table
exception: in some cases iterable doesn't make sense, e.g. spair() sorts the input by definition, so there is no reason for it to accept an iterable, because the input needs to be "reified"; it can't operate on a "stream".
return iterable instead of table
mimic the pairs() or ipairs() interface if the function is intended to be used in a "for" loop.
when a result-or-error interface is needed, return result|nil, nil|errmsg:
---@return Foo|nil # Result object, or nil if not found.
---@return nil|string # Error message on failure, or nil on success.
Interface conventions
Where possible, these patterns apply to _both_ Lua and the API:
When accepting a buffer id, etc., 0 means "current buffer", nil means "all buffers". Likewise for window id, tabpage id, etc.
Any function signature that accepts a callback function should define the callback as the LAST parameter, if possible. This improves readability of calls by placing the less "noisy" arguments near the start.
filter(table, opts, function() … end)
filter(function() … end, table, opts)
"Enable" ("toggle") interface and behavior:
enable(…, nil) and enable(…, {buf=nil}) are synonyms and control the the "global" enablement of a feature.
is_enabled(nil) and is_enabled({buf=nil}), likewise, query the global state of the feature.
enable(…, {buf: number}) sets a buffer-local "enable" flag.
is_enabled({buf: number}), likewise, queries the buffer-local state of the feature.
See vim.lsp.inlay_hint.enable() and vim.lsp.inlay_hint.is_enabled() for a reference implementation of these "best practices".


See also dev-naming.
When adding an API, check the following:
What precedents did you draw from? How does your solution compare to them?
Does your new API allow future expansion? How? Or why not?
Is the new API similar to existing APIs? Do we need to deprecate the old ones?
Did you cross-reference related concepts in the docs?
Avoid "mutually exclusive" parameters--via constraints or limitations, if necessary. For example nvim_create_autocmd() has mutually exclusive "callback" and "command" args; but the "command" arg could be eliminated by simply not supporting Vimscript function names, and treating a string "callback" arg as an Ex command (which can call Vimscript functions). The "buffer" arg could also be eliminated by treating a number "pattern" as a buffer number.
Avoid functions that depend on cursor position, current buffer, etc. Instead the function should take a position parameter, buffer parameter, etc.
Where things go
API (libnvim/RPC): exposes low-level internals, or fundamental things (such as nvim_exec_lua()) needed by clients or C consumers.
Lua stdlib = high-level functionality that builds on top of the API.


Naming is exceedingly important: the name of a thing is the primary interface for uses it, discusses it, searches for it, shares it... Consistent naming in the stdlib, API, and UI helps both users and developers discover and intuitively understand related concepts ("families"), and reduces cognitive burden. Discoverability encourages code re-use and likewise avoids redundant, overlapping mechanisms, which reduces code surface-area, and thereby minimizes bugs...
Naming conventions
In general, look for precedent when choosing a name, that is, look at existing (non-deprecated) functions. In particular, see below...
dev-name-common Use existing common {verb} names (actions) if possible:
add: Appends or inserts into a collection
attach: Listens to something to get events from it (TODO: rename to "on"?)
call: Calls a function
cancel: Cancels or dismisses an event or interaction, typically user-initiated and without error. (Compare "abort", which cancels and signals error/failure.)
clear: Clears state but does not destroy the container
create: Creates a new (non-trivial) thing (TODO: rename to "def"?)
del: Deletes a thing (or group of things)
detach: Dispose attached listener (TODO: rename to "un"?)
enable: Enables/disables functionality. Signature should be enable(enable?:boolean, filter?:table).
eval: Evaluates an expression
exec: Executes code, may return a result
fmt: Formats
get: Gets things (often by a query)
inspect: Presents a high-level, often interactive, view
is_enabled: Checks if functionality is enabled.
open: Opens something (a buffer, window, …)
parse: Parses something into a structured form
set: Sets a thing (or group of things)
start: Spin up a long-lived process. Prefer "enable" except when "start" is obviously more appropriate.
stop: Inverse of "start". Teardown a long-lived process.
try_{verb}: Best-effort operation, failure returns null or error obj
Do NOT use these deprecated verbs:
disable: Prefer enable(enable: boolean).
exit: Prefer "cancel" (or "stop" if appropriate).
is_disabled: Prefer is_enabled().
list: Redundant with "get"
notify: Redundant with "print", "echo"
show: Redundant with "print", "echo"
toggle: Prefer enable(not is_enabled()).
Use consistent names for {topic} in API functions: buffer is called "buf" everywhere, not "buffer" in some places and "buf" in others.
buf: Buffer
chan: channel
cmd: Command
cmdline: Command-line UI or input
fn: Function
hl: Highlight
pos: Position
proc: System process
tabpage: Tabpage
win: Window
Do NOT use these deprecated nouns:
buffer Use "buf" instead
callback Use on_foo instead
command Use "cmd" instead
window Use "win" instead
dev-name-events Use the "on_" prefix to name event-handling callbacks and also the interface for "registering" such handlers (on_key). The dual nature is acceptable to avoid a confused collection of naming conventions for these related concepts.
Editor events (autocommands) are historically named like:
Use this format to name API (RPC) events:
dev-api-name Use this format to name new RPC API functions:
Do not add new nvim_buf/nvim_win/nvim_tabpage APIs, unless you are certain the concept will NEVER be applied to more than one "scope". That is, {topic} should be the TOPIC ("ns", "extmark", "option", …) that acts on the scope(s) (buf/win/tabpage/global), it should NOT be the scope. Instead the scope should be a parameter (typically manifest as mutually-exclusive buf/win/… flags like nvim_get_option_value(), or less commonly as a scope: string field like nvim_get_option_info2()).
Example: nvim_get_keymap('v') operates in a global context (first parameter is not a Buffer). The "get" verb indicates that it gets anything matching the given filter parameter. A "list" verb is unnecessary because nvim_get_keymap('') (empty filter) returns all items.
Example: nvim_buf_del_mark acts on a Buffer object (the first parameter) and uses the "del" {verb}.

INTERFACE PATTERNS dev-api-patterns

Prefer adding a single nvim_{topic}_{verb}_… interface for a given topic.
  ns_id: int,
  filter: {
    handle: integer (buf/win/tabpage id)
    scope: "global" | "win" | "buf" | "tabpage"
): { ok: boolean }
  ns_id: int,
  filter: {
    handle: integer (buf/win/tabpage id)
    scope: "global" | "win" | "buf" | "tabpage"
): { ids: int[] }
  ns_id: int,
  filter: {
    handle: integer (buf/win/tabpage id)
    scope: "global" | "win" | "buf" | "tabpage"
): { ok: boolean }
Creating separate nvim_xx, nvim_buf_xx, nvim_win_xx, and nvim_tabpage_xx, functions all for the same xx topic, requires 4x the amount of documentation, tests, boilerplate, and interfaces, which users must comprehend, maintainers must maintain, etc. Thus the following is NOT recommended (compare these 12(!) functions to the above 3 functions):

API-CLIENT dev-api-client

api-client API clients wrap the Nvim API to provide idiomatic "SDKs" for their respective platforms (see jargon). You can build a new API client for your favorite platform or programming language.
node-client pynvim These clients can be considered the "reference implementation" for API clients:
Standard Features
API clients exist to hide msgpack-rpc details. The wrappers can be automatically generated by reading the api-metadata from Nvim. api-mapping
Clients should call nvim_set_client_info() after connecting, so users and plugins can detect the client by handling the ChanInfo event. This avoids the need for special variables or other client hints.
Clients should handle nvim_error_event notifications, which will be sent if an async request to nvim was rejected or caused an error.
Package Naming
API client packages should NOT be named something ambiguous like "neovim" or "python-client". Use "nvim" as a prefix/suffix to some other identifier following ecosystem conventions.
For example, Python packages tend to have "py" in the name, so "pynvim" is a good name: it's idiomatic and unambiguous. If the package is named "neovim", it confuses users, and complicates documentation and discussions.
Examples of API-client package names:
GOOD: nvim-racket
GOOD: pynvim
BAD: python-client
BAD: neovim_
API client implementation guidelines
Separate the transport layer from the rest of the library. rpc-connecting
Use a MessagePack library that implements at least version 5 of the MessagePack spec, which supports the BIN and EXT types used by Nvim.
Use a single-threaded event loop library/pattern.
Use a fiber/coroutine library for the language being used for implementing a client. These greatly simplify concurrency and allow the library to expose a blocking API on top of a non-blocking event loop without the complexity that comes with preemptive multitasking.
Don't assume anything about the order of responses to RPC requests.
Clients should expect requests, which must be handled immediately because Nvim is blocked while waiting for the client response.
Clients should expect notifications, but these can be handled "ASAP" (rather than immediately) because they won't block Nvim.
For C/C++ projects, consider libmpack instead of the library. libmpack is small (no dependencies, can inline into your C/C++ project) and efficient (no allocations). It also implements msgpack-RPC, the protocol required by Nvim.


External UIs should be aware of the api-contract. In particular, future versions of Nvim may add new items to existing events. The API is strongly backwards-compatible, but clients must not break if new (optional) fields are added to existing events.
Standard Features
External UIs are expected to implement these common features:
Call nvim_set_client_info() after connecting, so users and plugins can detect the UI by handling the ChanInfo event. This avoids the need for special variables and UI-specific config files (gvimrc, macvimrc, …).
Cursor style (shape, color) should conform to the 'guicursor' properties delivered with the mode_info_set UI event.
Send the ALT/META ("Option" on macOS) key as a <M- chord.
Send the "super" key (Windows key, Apple key) as a <D- chord.
Avoid mappings that conflict with the Nvim keymap-space; GUIs have many new chords (<C-,> <C-Enter> <C-S-x> <D-x>) and patterns ("shift shift") that do not potentially conflict with Nvim defaults, plugins, etc.
Consider the "option_set" ui-global event as a hint for other GUI behaviors. Various UI-related options ('guifont', 'ambiwidth', …) are published in this event. See also "mouse_on", "mouse_off".
UIs generally should NOT set $NVIM_APPNAME (unless explicitly requested by the user).
Support the text decorations/attributes given by ui-event-hl_attr_define. The "url" attr should be presented as a clickable hyperlink.
Commands index
Quick reference