Can t build create-react-app project with custom PUBLIC URL

Question

I m trying   PUBLIC URL http   example com npm run build   with a project built using the latest create-react-script   However  the occurrences of  PUBLIC URL  in public index html are replaced with an empty string  not the expected value PUBLIC URL   public index html contains code like   lt script src   PUBLIC URL  static js jarvis widget min js  gt  lt  script gt    Hours of searching the internet and stack overflow show that very little is written about PUBLIC URL  I cloned create-react-app from GitHub and have been browsing the code but have not yet been enlightened   Does anyone have any suggestions as to what I m doing wrong

User · Answer

That is not how the PUBLIC URL variable is used  According to the documentation  you can use the PUBLIC URL in your HTML    lt link rel  shortcut icon  href   PUBLIC URL  favicon ico  gt   Or in your JavaScript   render          Note  this is an escape hatch and should be used sparingly       Normally we recommend using  import  for getting asset URLs      as described in    Adding Images and Fonts    above this section    return  lt img src  process env PUBLIC URL     img logo png     gt       The PUBLIC URL is not something you set to a value of your choosing  it is a way to store files in your deployment outside of Webpack s build system   To view this  run your CRA app and add this to the src index js file   console log  public url     process env PUBLIC URL   You ll see the URL already exists   Read more in the CRA docs

User · Answer

Have a look at the documentation  You can have a  env file which picks up the PUBLIC URL  Although you should remember that what its used for -      You may use this variable to force assets to be referenced verbatim to   the url you provide  hostname included   This may be particularly   useful when using a CDN to host your application

User · Answer

People like me who are looking for something like this in in build   lt script type  quot text javascript quot  src  quot https   dsomething cloudfront net static js main ec7f8972 js quot  gt   Then setting https   dsomething cloudfront net to homepage in package json will not work  1  Quick Solution Build your project like this   windows  set PUBLIC URL https   dsomething cloudfront net amp  amp npm run build   linux mac  PUBLIC URL https   dsomething cloudfront net npm run build  And you will get  lt script type  quot text javascript quot  src  quot https   dsomething cloudfront net static js main ec7f8972 js quot  gt   in your built index html 2  Permanent  amp  Recommended Solution Create a file called  env at your project root same place where package json is located   In this file write this no quotes around the url   PUBLIC URL https   dsomething cloudfront net  Build your project as usual  npm run build  This will also generate index html with   lt script type  quot text javascript quot  src  quot https   dsomething cloudfront net static js main ec7f8972 js quot  gt   3   Weird Solution  Will do not work in latest react-scripts version  Add this in your package json  quot homepage quot    quot http      dsomething cloudfront net quot   Then index html will be generated with   lt script type  quot text javascript quot  src  quot   dsomething cloudfront net static js main ec7f8972 js quot  gt   Which is basically the same as   lt script type  quot text javascript quot  src  quot https   dsomething cloudfront net static js main ec7f8972 js quot  gt   in my understanding  Github Issue Github Comment

User · Answer

Not sure why you aren t able to set it  In the source  PUBLIC URL takes precedence over homepage  const envPublicUrl   process env PUBLIC URL      const getPublicUrl   appPackageJson   gt    envPublicUrl    require appPackageJson  homepage    You can try setting breakpoints in their code to see what logic is overriding your environment variable

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This problem becomes apparent when you try to host a react app in github pages   How I fixed this   In in my main application file  called app tsx  where I include the router  I set the basename  eg   lt BrowserRouter basename   Seans-TypeScript-ReactJS-Redux-Boilerplate   gt   Note that it is a relative url  this completely simplifies the ability to run locally and hosted   The basename value  matches the repository title on GitHub  This is the path that GitHub pages will auto create   That is all I needed to do   See working example hosted on GitHub pages at  https   sean-bradley github io Seans-TypeScript-ReactJS-Redux-Boilerplate

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If you see there source code they check if process env NODE ENV      development  returns true  and they automatically removes host URL and only return path  For example  if you set like below PUBLIC URL http   example com static   They will remove http   example com and only return  static  However since you only set root URL like http   example com  they will just return an empty string since there no subpath in your URL string  This only happens if you call react-scripts start  and if you call react-scripts build then isEnvDevelopment will be false  so it will just return http   example com as what you set in the  env file  Here is the source code of getPublicUrlOrPath js         Returns a URL or a path with slash at the end    In production can be URL  abolute path  relative path    In development always will be an absolute path    In development can use  path  module functions for operations        param  boolean  isEnvDevelopment     param   string undefined   homepage a valid url or pathname     param   string undefined   envPublicUrl a valid url or pathname     returns  string      function getPublicUrlOrPath isEnvDevelopment  homepage  envPublicUrl      const stubDomain    https   create-react-app dev      if  envPublicUrl           ensure last slash exists     envPublicUrl   envPublicUrl endsWith              envPublicUrl         envPublicUrl                validate if  envPublicUrl  is a URL or path like         stubDomain  is ignored if  envPublicUrl  contains a domain     const validPublicUrl   new URL envPublicUrl  stubDomain        return isEnvDevelopment         envPublicUrl startsWith                              validPublicUrl pathname            Some apps do not use client-side routing with pushState             For these   quot homepage quot  can be set to  quot   quot  to enable relative asset paths          envPublicUrl         if  homepage           strip last slash if exists     homepage   homepage endsWith        homepage   homepage                validate if  homepage  is a URL or path like and use just pathname     const validHomepagePathname   new URL homepage  stubDomain  pathname      return isEnvDevelopment         homepage startsWith                              validHomepagePathname            Some apps do not use client-side routing with pushState           For these   quot homepage quot  can be set to  quot   quot  to enable relative asset paths        homepage startsWith              homepage         validHomepagePathname         return

User · Answer

If the other answers aren t working for you  there s also a homepage field in package json  After running npm run build you should get a message like the following   The project was built assuming it is hosted at the server root  To override this  specify the homepage in your package json  For example  add this to build it for GitHub Pages      homepage     http   myname github io myapp     You would just add it as one of the root fields in package json  e g                 scripts                        homepage    https   example com      When it s successfully set  either via homepage or PUBLIC URL  you should instead get a message like this   The project was built assuming it is hosted at https   example com  You can control this with the homepage field in your package json

User · Answer

Actually the way of setting environment variables is different between different Operating System   Windows  cmd exe   set PUBLIC URL http   xxxx com amp  amp npm start    Note  the lack of whitespace is intentional    Linux  macOS  Bash    PUBLIC URL http   xxxx com npm start   Recommended  cross-env       scripts          serve    cross-env PUBLIC URL http   xxxx com npm start          ref  create-react-app README md adding-temporary-environment-variables-in-your-shell at master    facebookincubator create-react-app

User · Answer

As documented here create-react-app will only import environment variables beginning with REACT APP   so the PUBLIC URL  I believe  as mentioned by  redbmk  comes from the homepage setting in the package json file

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