# ndb [](https://travis-ci.com/GoogleChromeLabs/ndb) [](https://npmjs.org/package/ndb) > ndb is an improved debugging experience for Node.js, enabled by Chrome DevTools ## Installation Compatibility: ndb requires Node >=8.0.0. It works best with Node >=10. Installation: ndb depends on [Puppeteer](https://github.com/GoogleChrome/puppeteer) which downloads a recent version of Chromium (~170MB Mac, ~280MB Linux, ~280MB Win). ```bash # global install with npm: npm install -g ndb # alternatively, with yarn: yarn global add ndb ``` Global installation may fail with different permission errors, you can find help in this [thread](https://github.com/GoogleChromeLabs/ndb/issues/20). Windows users: Installation may fail on Windows during compilation the native dependencies. The following command may help: `npm install -g windows-build-tools` ### Local install If you want ndb available from an npm script (eg. `npm run debug` runs `ndb index.js`), you can install it as a development dependency: ```bash # local install with npm: npm install --save-dev ndb # alternatively, with yarn: yarn add ndb --dev ``` You can then [set up an npm script](https://docs.npmjs.com/misc/scripts#examples). In this case, ndb will not be available in your system path. ## Getting Started You can start debugging your Node.js application using one of the following ways: - Use `ndb` instead of the `node` command ```bash ndb server.js # Alternatively, you can prepend `ndb` ndb node server.js ``` - Prepend `ndb` in front of any other binary ```bash # If you use some other binary, just prepend `ndb` ## npm run unit ndb npm run unit # Debug any globally installed package ## mocha ndb mocha # To use a local binary, use `npx` and prepend before it ndb npx mocha ``` - Launch `ndb` as a standalone application - Then, debug any npm script from your `package.json`, e.g. unit tests ```bash # cd to your project folder (with a package.json) ndb . # In Sources panel > "NPM Scripts" sidebar, click the selected "Run" button ``` - Use `Ctrl`/`Cmd` + `R` to restart last run - Run any node command from within ndb's integrated terminal and ndb will connect automatically - Run any open script source by using 'Run this script' context menu item, ndb will connect automatically as well - Use `--prof` flag to profile your app, `Ctrl`/`Cmd` + `R` restarts profiling ```bash ndb --prof npm run unit ``` ## What can I do? `ndb` has some powerful features exclusively for Node.js: 1. Child processes are detected and attached to. 1. You can place breakpoints before the modules are required. 1. You can edit your files within the UI. On Ctrl-S/Cmd-S, DevTools will [save the changes to disk](https://developers.google.com/web/tools/chrome-devtools/workspaces/). 1. By default, ndb [blackboxes](https://developers.google.com/web/tools/chrome-devtools/javascript/reference#blackbox) all scripts outside current working directory to improve focus. This includes node internal libraries (like `_stream_wrap.js`, `async_hooks.js`, `fs.js`) This behaviour may be changed by "Blackbox anything outside working dir" setting. In addition, you can use all the DevTools functionality that you've used in [typical Node debugging](https://medium.com/@paul_irish/debugging-node-js-nightlies-with-chrome-devtools-7c4a1b95ae27): - breakpoint debugging, async stacks (AKA long stack traces), [async stepping](https://developers.google.com/web/updates/2018/01/devtools#async), etc... - console (top-level await, object inspection, advanced filtering) - [eager evaluation](https://developers.google.com/web/updates/2018/05/devtools#eagerevaluation) in console (requires Node >= 10) - JS sampling profiler - memory profiler ### Screenshot  ## Contributing Check out [contributing guide](https://github.com/GoogleChromeLabs/ndb/blob/master/CONTRIBUTING.md) to get an overview of ndb development. #### Thanks to the 'OG' `ndb` In early 2011, [@smtlaissezfaire](https://github.com/smtlaissezfaire) released the first serious debugger for Node.js, under the `ndb` package name. It's still preserved at [github.com/smtlaissezfaire/ndb](https://github.com/smtlaissezfaire/ndb#readme). We thank Scott for generously donating the package name.