请问你编译的时候，没有提示吗？
Replace Autoprefixer browsers option to Browserslist config.
  Use browserslist key in package.json or .browserslistrc file.

  Using browsers option cause some error. Browserslist config
  can be used for Babel, Autoprefixer, postcss-normalize and other tools.

  If you really need to use option, rename it to overrideBrowserslist.

  Learn more at:
  https://github.com/browserslist/browserslist#readme
  https://twitter.com/browserslist

摘自postcss/postcss-loader的github。
After setting up your postcss.config.js, add postcss-loader to your webpack.config.js. You can use it standalone or in conjunction with css-loader (recommended). Use it after css-loader and style-loader, but before other preprocessor loaders like e.g sass|less|stylus-loader, if you use any.
老师，您写的顺序是否是有问题的，可又未见有什么影响。请教老师。

webpack-cli：3.3.3 版本会提示 TypeError: process.getuid is not a function，更新即可
autoprefixer：
1. 会提示 Replace Autoprefixer browsers option to Browserslist config.
  Use browserslist key in package.json or .browserslistrc file.
将 browsers 参数换成 browserslist 放到 package.json 即可
2. 提示 You did not set any plugins, parser, or stringifier. Right now, PostCSS does nothing. Pick plugins for your case on https://www.postcss.parts/ and use them in postcss.config.js.
根目录创建 postcss.config.js 放 postcss-loader 的配置即可

老师好，我在按照教程使用的时候发现autoprefixer未生效，postcss-loader版本是3.0.0，错误提示：
You did not set any plugins, parser, or stringifier. Right now, PostCSS does nothing. Pick plugins for your case on https://www.postcss.parts/ and use them in postcss.config.js.

当我安装官网增加了postcss.config.js 后生效，想请问下原因，另外您觉得像这些帮助开发的工具是单独在项目根目录下写配置文件好还是在webpack配置里面写比较好？感觉写外面可扩展性比较强，之后再改的话直接修改外面的配置文件就可以了，但是会造成项目中根目录下配置文件很多，如babel/eslint/stylelint等等
module.exports = {
  plugins: [
    require('autoprefixer')
  ]
}

老师 我这样写 没警告了 但是前缀还是没加上 谢谢老师

loader: 'postcss-loader',
                        options: {
                            plugins: () => {
                                require('autoprefixer')({
                                    overrideBrowserslist: ['last 2 version', '>1%', 'ios 7']
                                })
                            }
                        }

老师为什么我写了
{
        test: /\.less$/,
        use: [
          // "style-loader",
          MiniCssExtractPlugin.loader, // 不将css文件插入到style中，直接抽离
          { loader: "css-loader" },
          {
            loader: "postcss-loader",
            options: {
              plugins: [require("autoprefixer")]
            }
          }, // 为了加属性前缀,一定要写在css-loader后面
          { loader: "less-loader" }
        ]
      },
打包后为什么没有前缀呢？我都安装了postcss-loader以及autoprefixer

ERROR in ./app/component/download/download.scss (./node_modules/css-loader/dist/cjs.js!./node_modules/sass-loader/lib/loader.js!./node_modules/postcss-loader/src??ref--6-3!./app/component/download/download.scss)
    Module build failed (from ./node_modules/postcss-loader/src/index.js):
    SyntaxError
    
    (4:8) Unknown word
    
      2 |
      3 | .down {
    > 4 | // height:5.1rem;
        | ^
      5 | padding: 0 .8rem;
      6 | color: #fff;
    
请问老师，autoprefixer 不能解析行内注释，这问题，应该怎么解。百度了大半天，都没找到解决办法！求解！

ERROR in ./src/search.less (./node_modules/css-loader/dist/cjs.js!./node_modules/less-loader/dist/cjs.js!./node_modules/Postcss-loader/src??ref--6-3!./src/search.less)
    Module build failed (from ./node_modules/Postcss-loader/src/index.js):
    BrowserslistError: Unknown browser query `ios7`. Maybe you are using old Browserslist or made typo in query.
        at unknownQuery (D:\webpack\my-project\node_modules\browserslist\index.js:201:10)
        at Function.select (D:\webpack\my-project\node_modules\browserslist\index.js:962:15)
        at D:\webpack\my-project\node_modules\browserslist\index.js:252:33
        at Array.reduce (<anonymous>)
        at resolve (D:\webpack\my-project\node_modules\browserslist\index.js:234:18)
        at browserslist (D:\webpack\my-project\node_modules\browserslist\index.js:353:16)
        at Browsers.parse (D:\webpack\my-project\node_modules\autoprefixer\lib\browsers.js:66:12)
        at new Browsers (D:\webpack\my-project\node_modules\autoprefixer\lib\browsers.js:48:26)
        at loadPrefixes (D:\webpack\my-project\node_modules\autoprefixer\lib\autoprefixer.js:101:20)
        at plugin (D:\webpack\my-project\node_modules\autoprefixer\lib\autoprefixer.js:112:20)
        at LazyResult.run (D:\webpack\my-project\node_modules\postcss\lib\lazy-result.js:295:14)
        at LazyResult.asyncTick (D:\webpack\my-project\node_modules\postcss\lib\lazy-result.js:208:26)
        at D:\webpack\my-project\node_modules\postcss\lib\lazy-result.js:250:14
        at new Promise (<anonymous>)
        at LazyResult.async (D:\webpack\my-project\node_modules\postcss\lib\lazy-result.js:246:23)
        at LazyResult.then (D:\webpack\my-project\node_modules\postcss\lib\lazy-result.js:127:17)
        at Promise.resolve.then.then (D:\webpack\my-project\node_modules\Postcss-loader\src\index.js:142:8)

关于autoprefixer的选项，我看官方文档，可以在postcss-preset-env里设置，是吗老师？

postcss-preset-env includes autoprefixer, so adding it separately is not necessary if you already use the preset.


来源：https://webpack.js.org/loaders/postcss-loader/#autoprefixing