URL-Encoding Bodies

By default, axios serializes JavaScript objects to JSON . To send data in the application/x-www-form-urlencoded format instead, you can use one of the following approaches.

Browser

In a browser, you can use the URLSearchParams API as follows:

const params = new URLSearchParams();
params.append('param1', 'value1');
params.append('param2', 'value2');
axios.post('/foo', params);
Note that URLSearchParams is not supported by all browsers (see caniuse.com), but there is a polyfill available (make sure to polyfill the global environment).
Alternatively, you can encode data using the qs library:
const qs = require('qs');
axios.post('/foo', qs.stringify({ 'bar': 123 }));
Or in another way (ES6),
import qs from 'qs';
const data = { 'bar': 123 };
const options = {
  method: 'POST',
  headers: { 'content-type': 'application/x-www-form-urlencoded' },
  data: qs.stringify(data),
  url,
axios(options);
Node.js
Query string
In node.js, you can use the querystring module as follows:
const querystring = require('querystring');
axios.post('http://something.com/', querystring.stringify({ foo: 'bar' }));
or 'URLSearchParams' from 'url module' as follows:
const url = require('url');
const params = new url.URLSearchParams({ foo: 'bar' });
axios.post('http://something.com/', params.toString());
You can also use the qs library.
Note: The qs library is preferable if you need to stringify nested objects, as the querystring method has known issues with that use case (https://github.com/nodejs/node-v0.x-archive/issues/1665).
🆕 Automatic serialization
Axios will automatically serialize the data object to urlencoded format if the content-type header is set to application/x-www-form-urlencoded.
This works both in the browser and in node.js:
const data = {
  x: 1,
  arr: [1, 2, 3],
  arr2: [1, [2], 3],
  users: [{name: 'Peter', surname: 'Griffin'}, {name: 'Thomas', surname: 'Anderson'}],
await axios.post('https://postman-echo.com/post', data,
  {headers: {'content-type': 'application/x-www-form-urlencoded'}}
The server will handle it as
    x: '1',
    'arr[]': [ '1', '2', '3' ],
    'arr2[0]': '1',
    'arr2[1][0]': '2',
    'arr2[2]': '3',
    'arr3[]': [ '1', '2', '3' ],
    'users[0][name]': 'Peter',
    'users[0][surname]': 'griffin',
    'users[1][name]': 'Thomas',
    'users[1][surname]': 'Anderson'
If your server framework's request body parser (like body-parser of express.js) supports nested objects decoding,
you will automatically receive the same server object that you submitted.
Echo server example (express.js) :
  var app = express();
  app.use(bodyParser.urlencoded({ extended: true })); // support url-encoded bodies
  app.post('/', function (req, res, next) {
     res.send(JSON.stringify(req.body));
  });
  server = app.listen(3000);