You might be wondering why yet another completion engine since there is the already widely used [YouCompleteMe](https://github.com/Valloric/YouCompleteMe) and [deoplete.nvim](https://github.com/Shougo/deoplete.nvim). Below are the reasons that led coc.nvim to build its own engine: - **Full LSP completion support**, especially snippet and `additionalTextEdit` feature, you'll understand why it's awesome when you experience it with a coc extension like `coc-tsserver`. - **Asynchronous and parallel completion request**, unless using vim sources, your vim will never be blocked. - **Does completion resolving on completion item change**. The details from completion items are echoed after being selected, this feature requires the `CompleteChanged` autocmd to work. - **Incomplete request and cancel request support**, only incomplete completion requests would be triggered on filtering completion items and cancellation requests are sent to servers only when necessary. - **Start completion without timer**. The completion will start after you type the first letter of a word by default and is filtered with new input after the completion has finished. Other completion engines use a timer to trigger completion so you always have to wait after the typed character. - **Realtime buffer keywords**. Coc will generate buffer keywords on buffer change in the background (with debounce), while some completion engines use a cache which isn't always correct. Plus, [Locality bonus feature](https://code.visualstudio.com/docs/editor/intellisense#_locality-bonus) from VSCode is enabled by default. - **Filter completion items when possible.** When you do a fuzzy filter with completion items, some completion engines will trigger a new completion, but coc.nvim will filter the items when possible which makes it much faster. Filtering completion items on backspace is also supported.