What is the difference between --save and --save-dev

Question

What is the difference between  npm install  package name   and  npm install  package name  --save  and  npm install  package name  --save-dev  What does this mean  And what is really the effect of --save and -dev keywords

User · Answer

As suggested by  andreas-hultgren in this answer and according to the npm docs      If someone is planning on downloading and using your module in their program  then they probably don t want or need to download and build the external test or documentation framework that you use    However  for webapp development  Yeoman  a scaffolding tool that installs a peer-reviewed  pre-written package json file amongst other things  places all packages in devDependencies and nothing in dependencies  so it appears that the use of --save-dev is a safe bet in webapp development  at least

User · Answer

--save-dev  only used in the development  not in production   --save  production dependencies   --global or -g  used globally i e can be used anywhere in our local system

User · Answer

All explanations here are great  but lacking a very important thing  How do you install production dependencies only   without the development dependencies   We separate dependencies from devDependencies by using --save or --save-dev  To install all we use   npm i   To install only production packages we should use   npm i --only production

User · Answer

By default  NPM simply installs a package under node modules  When you re trying to install dependencies for your app module  you would need to first install them  and then add them to the dependencies section of your package json  --save-dev adds the third-party package to the package s development dependencies  It won t be installed when someone runs npm install directly to install your package  It s typically only installed if someone clones your source repository first and then runs npm install in it  --save adds the third-party package to the package s dependencies  It will be installed together with the package whenever someone runs npm install package  Dev dependencies are those dependencies that are only needed for developing the package  That can include test runners  compilers  packagers  etc  Both types of dependencies are stored in the package s package json file  --save adds to dependencies  --save-dev adds to devDependencies npm install documentation can be referred here  -- Please note that --save is now the default option  since NPM 5  Therefore  it is not explicitly needed anymore  It is possible to run npm install without the --save to achieve the same result

User · Answer

People use npm on production to do wicked cool stuff  Node js is an example of this  so you don t want all your dev tools being run   If you are using gulp  or similar  to create build files to put on your server then it doesn t really matter

User · Answer

The difference between --save and --save-dev may not be immediately noticeable if you have tried them both on your own projects  So here are a few examples     Lets say you were building an app that used the moment package to parse and display dates  Your app is a scheduler so it really needs this package to run  as in  cannot run without it  In this case you would use  npm install moment --save   This would create a new value in your package json   dependencies                moment     2 17 1      When you are developing  it really helps to use tools such as test suites and may need jasmine-core and karma  In this case you would use  npm install jasmine-core --save-dev npm install karma --save-dev   This would also create a new value in your package json   devDependencies                  jasmine-core     2 5 2        karma     1 4 1       You do not need the test suite to run the app in its normal state  so it is a --save-dev type dependency  nothing more  You can see how if you do not understand what is really happening  it is a bit hard to imagine   Taken directly from NPM docs docs dependencies     Dependencies      Dependencies are specified in a simple object that maps a package name   to a version range  The version range is a string which has one or   more space-separated descriptors  Dependencies can also be identified   with a tarball or git URL       Please do not put test harnesses or transpilers in your dependencies   object  See devDependencies  below    Even in the docs  it asks you to use --save-dev for modules such as test harnesses    I hope this helps and is clear

User · Answer

Basically We Write npm install package name  But specially for Testing Purpose we don t need to run some package while Application is Running in Normal State so that Node introduce good way to solve this problem  Whenever we write npm install package name --save-dev  at that time this package is only installed for development purpose

User · Answer

--save-dev is used for modules used in development of the application not require while running it in production envionment --save is used to add it in package json and it is required for running of the application   Example  express body-parser lodash helmet mysql all these are used while running the application use --save to put in dependencies while mocha istanbul chai sonarqube-scanner all are used during development  so put those in dev-dependencies    npm link or npm install will also install the dev-dependency modules along with dependency modules in your project folder

User · Answer

--save-dev is used to save the package for development purpose  Example  unit tests  minification    --save is used to save the package required for the application to run

User · Answer

--save-dev saves semver spec into  devDependencies  array in your package descriptor file  --save saves it into  dependencies  instead

User · Answer

You generally don t want to bloat production package with things that you only intend to use for Development purposes    Use --save-dev  or -D  option to separate packages such as Unit Test frameworks  jest  jasmine  mocha  chai  etc     Any other packages that your app needs for Production  should be installed using --save  or -S    npm install --save lodash         prod dependency npm install -S moment                        npm install -S opentracing                    npm install -D jest                   dev only dependency npm install --save-dev typescript     dev only dependency   If you open the package json file then you will see these entries listed under two different sections    dependencies        lodash    4 x      moment    2 x      opentracing     0 14 1       devDependencies          jest    22 x        typescript     2 8 3

User · Answer

I want to add some my ideas as   I think all differents will appear when someone use your codes instead of using by yourself  For example  you write a HTTP library called node s request  In your library    you used lodash to handle string and object  without lodash  your codes cannot run  If someone use your HTTP library as a part of his codes  Your codes will be compiled with his    your codes need lodash  So you need put in dependencies to compile    If you write a project like monaco-editor  which is a web editor   you have bundle all your codes and your product env library using webpack  when build completed  only have a monaco-min js  So someone don t case whether --save or --save-dependencies  only he need is monaco-min js  Summary    If someone want to compile your codes  use as library      put lodash which used by your codes into dependencies If someone want add more feature to your codes  he need unit test and compiler  put these into dev-dependencies

User · Answer

Clear answers are already provided  But it s worth mentioning how devDependencies affects installing packages      By default  npm install will install all modules listed as dependencies in package json   With the --production flag  or when the NODE ENV environment variable is set to production    npm will not install modules listed in devDependencies     See  https   docs npmjs com cli install

User · Answer

A perfect example of this is     npm install typescript --save-dev   In this case  you d want to have Typescript  a javascript-parseable coding language  available for development  but once the app is deployed  it is no longer necessary  as all of the code has been transpiled to javascript  As such  it would make no sense to include it in the published app  Indeed  it would only take up space and increase download times

User · Answer

Let me give you an example     You are a developer of a very SERIOUS npm library  Which uses different testing libraries to test the package  An user Downloaded your library and want to use it in their code  Do they need to download your testing libraries as well  Maybe you use jest for testing and they use mocha  Do you want them to install jest as well  Just To run your library    No  right  That s why they are in devDependencies   When someone does  npm i yourPackage only the libraries required to RUN your library will be installed  Other libraries you used to bundle your code with or testing and mocking will not be installed because you put them in devDependencies  Pretty neat right   So  Why do the developers need to expose the devDependancies   Let s say your package is an open source package and 100s of people are sending pull requests to your package  Then how they will test the package  They will git clone your repo and when they would do an npm i the dependencies as well as devDependencies  Because they are not using your package  They are developing the package further  thus  in order to test your package they need to pass the existing test cases as well write new  So  they need to use your devDependencies which contain all the testing building mocking libraries that YOU used

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