React-router “Cannot GET /*” except for root url

If you are using webpack-dev-server there is an option called history-api-fallback. If set to true 404s will fallback to /index.html.

Add the option to devServer section of the Webpack config like this:

devServer: {
    contentBase: 'app/ui/www',
    devtool: 'eval',
    hot: true,
    inline: true,
    port: 3000,
    outputPath: buildPath,
    historyApiFallback: true,
},

Link to Webpack docs: https://webpack.js.org/configuration/dev-server/

webpack-dev-server docs on Github: https://github.com/webpack/webpack-dev-server