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</script></nav></div><div class="container mainContainer"><div class="wrapper"><div class="post"><header class="postHeader"><a class="edit-page-link button" href="https://github.com/facebook/create-react-app/edit/master/docusaurus/docs/adding-custom-environment-variables.md" target="_blank" rel="noreferrer noopener">Edit</a><h1 class="postHeaderTitle">Adding Custom Environment Variables</h1></header><article><div><span><blockquote>
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<p>Note: this feature is available with <code>react-scripts@0.2.3</code> and higher.</p>
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</blockquote>
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<p>Your project can consume variables declared in your environment as if they were declared locally in your JS files. By default you will have <code>NODE_ENV</code> defined for you, and any other environment variables starting with <code>REACT_APP_</code>.</p>
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<blockquote>
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<p>WARNING: Do not store any secrets (such as private API keys) in your React app!</p>
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<p>Environment variables are embedded into the build, meaning anyone can view them by inspecting your app's files.</p>
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</blockquote>
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<p><strong>The environment variables are embedded during the build time</strong>. Since Create React App produces a static HTML/CSS/JS bundle, it can’t possibly read them at runtime. To read them at runtime, you would need to load HTML into memory on the server and replace placeholders in runtime, just like <a href="/docs/title-and-meta-tags#injecting-data-from-the-server-into-the-page">described here</a>. Alternatively you can rebuild the app on the server anytime you change them.</p>
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<blockquote>
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<p>Note: You must create custom environment variables beginning with <code>REACT_APP_</code>. Any other variables except <code>NODE_ENV</code> will be ignored to avoid accidentally <a href="https://github.com/facebook/create-react-app/issues/865#issuecomment-252199527">exposing a private key on the machine that could have the same name</a>. Changing any environment variables will require you to restart the development server if it is running.</p>
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</blockquote>
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<p>These environment variables will be defined for you on <code>process.env</code>. For example, having an environment variable named <code>REACT_APP_NOT_SECRET_CODE</code> will be exposed in your JS as <code>process.env.REACT_APP_NOT_SECRET_CODE</code>.</p>
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<p>There is also a special built-in environment variable called <code>NODE_ENV</code>. You can read it from <code>process.env.NODE_ENV</code>. When you run <code>npm start</code>, it is always equal to <code>'development'</code>, when you run <code>npm test</code> it is always equal to <code>'test'</code>, and when you run <code>npm run build</code> to make a production bundle, it is always equal to <code>'production'</code>. <strong>You cannot override <code>NODE_ENV</code> manually.</strong> This prevents developers from accidentally deploying a slow development build to production.</p>
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<p>These environment variables can be useful for displaying information conditionally based on where the project is deployed or consuming sensitive data that lives outside of version control.</p>
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<p>First, you need to have environment variables defined. For example, let’s say you wanted to consume an environment variable inside a <code><form></code>:</p>
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<pre><code class="hljs css language-jsx">render() {
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<span class="hljs-keyword">return</span> (
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<span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>
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<span class="hljs-tag"><<span class="hljs-name">small</span>></span>You are running this application in <span class="hljs-tag"><<span class="hljs-name">b</span>></span>{process.env.NODE_ENV}<span class="hljs-tag"></<span class="hljs-name">b</span>></span> mode.<span class="hljs-tag"></<span class="hljs-name">small</span>></span>
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<span class="hljs-tag"><<span class="hljs-name">form</span>></span>
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<span class="hljs-tag"><<span class="hljs-name">input</span> <span class="hljs-attr">type</span>=<span class="hljs-string">"hidden"</span> <span class="hljs-attr">defaultValue</span>=<span class="hljs-string">{process.env.REACT_APP_NOT_SECRET_CODE}</span> /></span>
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<span class="hljs-tag"></<span class="hljs-name">form</span>></span>
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<span class="hljs-tag"></<span class="hljs-name">div</span>></span>
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);
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}
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</span></code></pre>
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<p>During the build, <code>process.env.REACT_APP_NOT_SECRET_CODE</code> will be replaced with the current value of the <code>REACT_APP_NOT_SECRET_CODE</code> environment variable. Remember that the <code>NODE_ENV</code> variable will be set for you automatically.</p>
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<p>When you load the app in the browser and inspect the <code><input></code>, you will see its value set to <code>abcdef</code>, and the bold text will show the environment provided when using <code>npm start</code>:</p>
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<!-- prettier-ignore-start -->
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<pre><code class="hljs css language-html"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>
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<span class="hljs-tag"><<span class="hljs-name">small</span>></span>You are running this application in <span class="hljs-tag"><<span class="hljs-name">b</span>></span>development<span class="hljs-tag"></<span class="hljs-name">b</span>></span> mode.<span class="hljs-tag"></<span class="hljs-name">small</span>></span>
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<span class="hljs-tag"><<span class="hljs-name">form</span>></span>
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<span class="hljs-tag"><<span class="hljs-name">input</span> <span class="hljs-attr">type</span>=<span class="hljs-string">"hidden"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"abcdef"</span> /></span>
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<span class="hljs-tag"></<span class="hljs-name">form</span>></span>
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<span class="hljs-tag"></<span class="hljs-name">div</span>></span>
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</code></pre>
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<!-- prettier-ignore-end -->
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<p>The above form is looking for a variable called <code>REACT_APP_NOT_SECRET_CODE</code> from the environment. In order to consume this value, we need to have it defined in the environment. This can be done using two ways: either in your shell or in a <code>.env</code> file. Both of these ways are described in the next few sections.</p>
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<p>Having access to the <code>NODE_ENV</code> is also useful for performing actions conditionally:</p>
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<pre><code class="hljs css language-js"><span class="hljs-keyword">if</span> (process.env.NODE_ENV !== <span class="hljs-string">'production'</span>) {
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analytics.disable();
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}
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</code></pre>
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<p>When you compile the app with <code>npm run build</code>, the minification step will strip out this condition, and the resulting bundle will be smaller.</p>
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<h2><a class="anchor" aria-hidden="true" id="referencing-environment-variables-in-the-html"></a><a href="#referencing-environment-variables-in-the-html" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Referencing Environment Variables in the HTML</h2>
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<blockquote>
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<p>Note: this feature is available with <code>react-scripts@0.9.0</code> and higher.</p>
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</blockquote>
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<p>You can also access the environment variables starting with <code>REACT_APP_</code> in the <code>public/index.html</code>. For example:</p>
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<pre><code class="hljs css language-html"><span class="hljs-tag"><<span class="hljs-name">title</span>></span>%REACT_APP_WEBSITE_NAME%<span class="hljs-tag"></<span class="hljs-name">title</span>></span>
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</code></pre>
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<p>Note that the caveats from the above section apply:</p>
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<ul>
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<li>Apart from a few built-in variables (<code>NODE_ENV</code> and <code>PUBLIC_URL</code>), variable names must start with <code>REACT_APP_</code> to work.</li>
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<li>The environment variables are injected at build time. If you need to inject them at runtime, <a href="/docs/title-and-meta-tags#generating-dynamic-meta-tags-on-the-server">follow this approach instead</a>.</li>
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</ul>
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<h2><a class="anchor" aria-hidden="true" id="adding-temporary-environment-variables-in-your-shell"></a><a href="#adding-temporary-environment-variables-in-your-shell" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Adding Temporary Environment Variables In Your Shell</h2>
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<p>Defining environment variables can vary between OSes. It’s also important to know that this manner is temporary for the life of the shell session.</p>
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<h3><a class="anchor" aria-hidden="true" id="windows-cmdexe"></a><a href="#windows-cmdexe" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Windows (cmd.exe)</h3>
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<pre><code class="hljs css language-cmd"><span class="hljs-built_in">set</span> "REACT_APP_NOT_SECRET_CODE=abcdef" && npm <span class="hljs-built_in">start</span>
|
||
</code></pre>
|
||
<p>(Note: Quotes around the variable assignment are required to avoid a trailing whitespace.)</p>
|
||
<h3><a class="anchor" aria-hidden="true" id="windows-powershell"></a><a href="#windows-powershell" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Windows (Powershell)</h3>
|
||
<pre><code class="hljs css language-Powershell">(<span class="hljs-variable">$env:REACT_APP_NOT_SECRET_CODE</span> = <span class="hljs-string">"abcdef"</span>) -and (npm start)
|
||
</code></pre>
|
||
<h3><a class="anchor" aria-hidden="true" id="linux-macos-bash"></a><a href="#linux-macos-bash" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Linux, macOS (Bash)</h3>
|
||
<pre><code class="hljs css language-sh">REACT_APP_NOT_SECRET_CODE=abcdef npm start
|
||
</code></pre>
|
||
<h2><a class="anchor" aria-hidden="true" id="adding-development-environment-variables-in-env"></a><a href="#adding-development-environment-variables-in-env" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Adding Development Environment Variables In <code>.env</code></h2>
|
||
<blockquote>
|
||
<p>Note: this feature is available with <code>react-scripts@0.5.0</code> and higher.</p>
|
||
</blockquote>
|
||
<p>To define permanent environment variables, create a file called <code>.env</code> in the root of your project:</p>
|
||
<pre><code class="hljs"><span class="hljs-attr">REACT_APP_NOT_SECRET_CODE</span>=abcdef
|
||
</code></pre>
|
||
<blockquote>
|
||
<p>Note: You must create custom environment variables beginning with <code>REACT_APP_</code>. Any other variables except <code>NODE_ENV</code> will be ignored to avoid <a href="https://github.com/facebook/create-react-app/issues/865#issuecomment-252199527">accidentally exposing a private key on the machine that could have the same name</a>. Changing any environment variables will require you to restart the development server if it is running.</p>
|
||
</blockquote>
|
||
<blockquote>
|
||
<p>Note: You need to restart the development server after changing <code>.env</code> files.</p>
|
||
</blockquote>
|
||
<p><code>.env</code> files <strong>should be</strong> checked into source control (with the exclusion of <code>.env*.local</code>).</p>
|
||
<h3><a class="anchor" aria-hidden="true" id="what-other-env-files-can-be-used"></a><a href="#what-other-env-files-can-be-used" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>What other <code>.env</code> files can be used?</h3>
|
||
<blockquote>
|
||
<p>Note: this feature is <strong>available with <code>react-scripts@1.0.0</code> and higher</strong>.</p>
|
||
</blockquote>
|
||
<ul>
|
||
<li><code>.env</code>: Default.</li>
|
||
<li><code>.env.local</code>: Local overrides. <strong>This file is loaded for all environments except test.</strong></li>
|
||
<li><code>.env.development</code>, <code>.env.test</code>, <code>.env.production</code>: Environment-specific settings.</li>
|
||
<li><code>.env.development.local</code>, <code>.env.test.local</code>, <code>.env.production.local</code>: Local overrides of environment-specific settings.</li>
|
||
</ul>
|
||
<p>Files on the left have more priority than files on the right:</p>
|
||
<ul>
|
||
<li><code>npm start</code>: <code>.env.development.local</code>, <code>.env.development</code>, <code>.env.local</code>, <code>.env</code></li>
|
||
<li><code>npm run build</code>: <code>.env.production.local</code>, <code>.env.production</code>, <code>.env.local</code>, <code>.env</code></li>
|
||
<li><code>npm test</code>: <code>.env.test.local</code>, <code>.env.test</code>, <code>.env</code> (note <code>.env.local</code> is missing)</li>
|
||
</ul>
|
||
<p>These variables will act as the defaults if the machine does not explicitly set them.<br>
|
||
Please refer to the <a href="https://github.com/motdotla/dotenv">dotenv documentation</a> for more details.</p>
|
||
<blockquote>
|
||
<p>Note: If you are defining environment variables for development, your CI and/or hosting platform will most likely need
|
||
these defined as well. Consult their documentation how to do this. For example, see the documentation for <a href="https://docs.travis-ci.com/user/environment-variables/">Travis CI</a> or <a href="https://devcenter.heroku.com/articles/config-vars">Heroku</a>.</p>
|
||
</blockquote>
|
||
<h3><a class="anchor" aria-hidden="true" id="expanding-environment-variables-in-env"></a><a href="#expanding-environment-variables-in-env" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Expanding Environment Variables In <code>.env</code></h3>
|
||
<blockquote>
|
||
<p>Note: this feature is available with <code>react-scripts@1.1.0</code> and higher.</p>
|
||
</blockquote>
|
||
<p>Expand variables already on your machine for use in your <code>.env</code> file (using <a href="https://github.com/motdotla/dotenv-expand">dotenv-expand</a>).</p>
|
||
<p>For example, to get the environment variable <code>npm_package_version</code>:</p>
|
||
<pre><code class="hljs"><span class="hljs-attr">REACT_APP_VERSION</span>=<span class="hljs-variable">$npm_package_version</span>
|
||
<span class="hljs-comment"># also works:</span>
|
||
<span class="hljs-comment"># REACT_APP_VERSION=${npm_package_version}</span>
|
||
</code></pre>
|
||
<p>Or expand variables local to the current <code>.env</code> file:</p>
|
||
<pre><code class="hljs"><span class="hljs-attr">DOMAIN</span>=www.example.com
|
||
<span class="hljs-attr">REACT_APP_FOO</span>=<span class="hljs-variable">$DOMAIN</span>/foo
|
||
<span class="hljs-attr">REACT_APP_BAR</span>=<span class="hljs-variable">$DOMAIN</span>/bar
|
||
</code></pre>
|
||
</span></div></article></div><div class="docLastUpdate"><em>Last updated on 5/5/2019 by Mostafa Nawara</em></div><div class="docs-prevnext"><a class="docs-prev button" href="/docs/adding-a-router"><span class="arrow-prev">← </span><span>Adding a Router</span></a><a class="docs-next button" href="/docs/making-a-progressive-web-app"><span>Making a Progressive Web App</span><span class="arrow-next"> →</span></a></div></div></div><nav class="onPageNav"><ul class="toc-headings"><li><a href="#referencing-environment-variables-in-the-html">Referencing Environment Variables in the HTML</a></li><li><a href="#adding-temporary-environment-variables-in-your-shell">Adding Temporary Environment Variables In Your Shell</a><ul class="toc-headings"><li><a href="#windows-cmdexe">Windows (cmd.exe)</a></li><li><a href="#windows-powershell">Windows (Powershell)</a></li><li><a href="#linux-macos-bash">Linux, macOS (Bash)</a></li></ul></li><li><a href="#adding-development-environment-variables-in-env">Adding Development Environment Variables In <code>.env</code></a><ul class="toc-headings"><li><a href="#what-other-env-files-can-be-used">What other <code>.env</code> files can be used?</a></li><li><a href="#expanding-environment-variables-in-env">Expanding Environment Variables In <code>.env</code></a></li></ul></li></ul></nav></div><footer class="nav-footer" id="footer"><section class="sitemap"><a href="/" class="nav-home"><img src="/img/logo.svg" alt="Create React App" width="66" height="58"/></a><div><h5>Docs</h5><a href="/docs/getting-started">Get Started</a><a href="https://reactjs.org/" target="_blank" rel="noreferrer noopener">Learn React</a></div><div><h5>Community</h5><a href="https://stackoverflow.com/questions/tagged/create-react-app" target="_blank" rel="noreferrer noopener">Stack Overflow</a><a href="https://spectrum.chat/create-react-app" target="_blank" rel="noreferrer noopener">Spectrum</a><a href="https://twitter.com/reactjs" target="_blank" rel="noreferrer noopener">Twitter</a></div><div><h5>More</h5><a href="https://www.github.com/facebook/create-react-app">GitHub</a><a class="github-button" href="https://github.com/facebook/create-react-app" data-icon="octicon-star" data-count-href="/facebook/create-react-app/stargazers" data-show-count="true" data-count-aria-label="# stargazers on GitHub" aria-label="Star this project on GitHub">Star</a></div></section><a href="https://code.facebook.com/projects/" target="_blank" rel="noreferrer noopener" class="fbOpenSource"><img src="/img/oss_logo.png" alt="Facebook Open Source" width="170" height="45"/></a><section class="copyright">Copyright © 2019 Facebook Inc.</section></footer></div><script type="text/javascript" src="https://cdn.jsdelivr.net/docsearch.js/1/docsearch.min.js"></script><script>
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