后端需要添加Access-Control-Allow-Origin头部，允许前端访问该资源。在服务器配置中增加一个CORS配置即可，示例代码如下：

//Express.js示例
app.use(function(req,res,next){
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
    next();
});

//Django示例
from django.http import HttpResponse

def my_view(request):
    response = HttpResponse('Hello world')
    response['Access-Control-Allow-Origin'] = '*'
    return response

同时需要注意，如果是使用fetch或者ajax等方式发起请求，需要添加mode:"cors"，示例如下：

fetch(url, {
    method: "POST",
    mode: "cors",
    headers: {
        "Content-Type": "application/x-www-form-urlencoded;charset=UTF-8"
    },
    body: ""
})