next.config.js

const path = require('path');
const withLess = require('@zeit/next-less');
const withPlugins = require('next-compose-plugins');
const OptimizeCssAssetsPlugin = require('optimize-css-assets-webpack-plugin');
const CleanCss = require('clean-css');

const nextConfig = {
	webpack(config) {
	   config.module.rules.push({
        test: /\.(png|svg|eot|otf|ttf|woff|woff2)$/,
        use: {
          loader: 'url-loader',
          options: {
            limit: 8192,
            publicPath: '/_next/static/',
            outputPath: 'static/',
            name: '[name].[ext]',
          },
        },
		});
		config.resolve.alias['../../theme.config$'] = path.join(config.context, '/semantic-ui/theme.config');
    config.plugins.push(
				new OptimizeCssAssetsPlugin({
					assetNameRegExp: /\.css$/g,
					cssProcessor: CleanCss,
					cssProcessorOptions: {
						sourceMap: true,
					},
					canPrint: true,
				})
			);
		return config;
	},
};

const plugins = [withLess];
module.exports = withPlugins(plugins, nextConfig);