description	The collection of useful snippet code for the Scripting tool

Snippet Code

1. What's it?

A collection of snippet Javascript code for the Scripting Tool.

{% hint style="info" %} Could not find the Snippet Code you are looking for?

Please open a ticket at https://github.com/ProxymanApp/Proxyman, we will get back to help you ⭐️ {% endhint %}

{% hint style="success" %} Use Proxyman MCP with your agent (Codex/Claude Code) to help you generate a Scripting easily 🚀 {% endhint %}

2. Common on Request and Response

Multipart/form-data

Read, add, update, or remove a part of multipart/form-data

3. Addons

3.1 Use `npm install`

use `npm install dayjs` to install 3rd npm packages

4. Regex

5. Import / Export Files

6. Miscellaneous

7. Encryption/Decryption

8. Map Remote with Scripting

9. Make Async/await HTTP Request (macOS)

9.1. Make Async/await HTTP Request (Windows/Linux)

Make a request with the Axios library

10. URL and URLSearchParams

URL and URLSearchParams

11. Access Environment Variables

Manually read system environment variables

12. Websocket

HTTP Header

Add/Update: Request or Response Header

function onRequest(context, url, request) {
    // Add or update Request Header
    request.headers["X-Proxyman-Key"] = "My-Value";
    request.headers.name = "Proxyman";
    return request;
}

function onResponse(context, url, request, response) {
    // Add or update Response Header
    response.headers["X-Proxyman-Key"] = "My-Value";
    response.headers.id = 100;
    return response;
}

Delete: Request or Response Header

function onRequest(context, url, request) {
    delete request.headers["X-Proxyman-Key"];
    return request;
}

function onResponse(context, url, request, response) {
    delete response.headers["X-Proxyman-Key"];
    return response;
}

Request Query

Add/Update

function onRequest(context, url, request) {
    request.queries["name"] = "Proxyman";
    request.queries["platform"] = "macOS";
    // => http://proxyman.io?name=Proxyman&platform=macOS
    return request;
}

Delete

function onRequest(context, url, request) {
    delete request.queries["name"];
    delete request.queries["platform"];
    return request;
}

URLEncoded Form Body

Add/Update

function onRequest(context, url, request) {
    // Make sure the Response Header is application/x-www-form-urlencoded
    // Content-Type: application/x-www-form-urlencoded   
    var formBody = request.body;

    formBody["name"] = "Proxyman";
    formBody["flatform"] = "macOS";

    request.body = formBody; // => name=Proxyman&platform=macOS
    return request;
}

Delete

function onRequest(context, url, request) {
    // Content-Type: application/x-www-form-urlencoded
    var formBody = request.body;

    delete formBody["name"];
    delete formBody["flatform"];

    request.body = formBody;
    return request;
}

Change Request Destination (scheme, host, port, path)

function onRequest(context, url, request) {
    request.scheme = "http";
    request.host = "proxyman.dev";
    request.port = 9090;
    request.path = "v1/data/user";
    return request;
}

Upstream ALPN and HTTP/2 settings

Available in Proxyman v26.0.0 or later for macOS. See HTTP/2 for setup.

Set request.upstream in onRequest to change how Proxyman connects to the server. Enable SSL Proxying for the HTTPS domain. H2 overrides also require HTTP/2 enabled in Settings and an HTTP/2 client connection to Proxyman.

async function onRequest(context, url, request) {
  request.upstream = {
    tls: { alpnProtocols: ["h2"] },
    http2: {
      headerTableSize: 65536,
      initialWindowSize: 6291456,
      maxHeaderListSize: 262144
    }
  };
  return request;
}

ALPN accepts a nonempty list with no duplicates:

["h2"]: Require HTTP/2. Fail if the server cannot use it.
["h2", "http/1.1"]: Allow HTTP/1.1 fallback.
["http/1.1"]: Use HTTP/1.1.

HTTP/2 values must be integers from 0 to the maximum below. Omitted or null fields use defaults.

Setting	Default	Maximum
`headerTableSize`	`65536`	`4294967295`
`initialWindowSize`	`6291456`	`2147483647`
`maxHeaderListSize`	`262144`	`4294967295`

To reset all overrides, delete request.upstream or set it to null. Invalid or incompatible settings return a local 502 Scripting error.

HTTP to HTTPS

function onRequest(context, url, request) {
    request.scheme = "http";
    request.port = 80; // Don't forget to override the port
    return request;
}

HTTPS to HTTP

function onRequest(context, url, request) {
    request.scheme = "https";
    request.port = 443; // Don't forget to override the port
    return request;
}

Change HTTP Request Method

function onRequest(context, url, request) {
    request.method = "POST";
    return request;
}

Change Response HTTP Status Code

function onResponse(context, url, request, response) {
    response.statusCode = 404;
    return response;
}

JSON Body

On Request

function onRequest(context, url, request) {
    // Set JSON content
    request.headers["Content-Type"] = "application/json";
    
    // Get Request body
    var jsonBody = request.body;
    
    // Modify data
    jsonBody["name"] = "Proxyman";
    jsonBody["flatform"] = "macOS";
    jsonBody["info"] = { 
                        "website": "proxyman.io",
                        "region": "Earth"
                       };
    // Set it again        
    request.body = jsonBody;
    return request;
}

On Response

function onResponse(context, url, request, response)  {
    // Set JSON content
    response.headers["Content-Type"] = "application/json";
  
    // Get Request body
    var jsonBody = response.body;
    
    // Modify data
    jsonBody["name"] = "Proxyman";
    jsonBody["flatform"] = "macOS";
    jsonBody["info"] = { 
                        "website": "proxyman.io",
                        "region": "Earth"
                       };
    // Set it again        
    response.body = jsonBody;
    return response;
}

Multipart/form-data

From Proxyman macOS 6.6.0 or later, you can read, add, delete a multipart/form-data

function onRequest(context, url, request) {
  // Only run for multipart requests
  if (!request.multipart) {
    return request;
  }

  var parts = request.multipart;

  // 1) List parts (debug)
  console.log("Multipart parts:", parts);

  // 2) Modify a text part by name
  for (var i = 0; i < parts.length; i++) {
    if (parts[i].name === "text_field") {
      var p = parts[i];
      p.body = "Updated text from script";
      parts[i] = p;
    }
  }

  // 3) Modify a file part by name (binary body as [UInt8])
  for (var i = 0; i < parts.length; i++) {
    if (parts[i].name === "file_field") {
      var p = parts[i];
      p.body = [72, 101, 108, 108, 111]; // "Hello"
      p.fileName = "hello.txt";
      p.contentType = "text/plain";
      parts[i] = p;
    }
  }

  // 4) Add a new text part
  parts.push({
    name: "new_field",
    body: "Added by script"
  });

  // 5) Remove a part by name
  var filtered = [];
  for (var i = 0; i < parts.length; i++) {
    if (parts[i].name !== "remove_me") {
      filtered.push(parts[i]);
    }
  }

  // Apply updates
  request.multipart = filtered;

  return request;
}

Map a local file to Response's Body like Map Local Tool (Proxyman 2.25.0+)

It's a convenient way to directly set a local file to a Body by using bodyFilePath property

// For request
request.bodyFilePath = "~/Desktop/image.png";

// For response
response.bodyFilePath = "~/Desktop/image.png";

function onResponse(context, url, request, response) {
 
  response.headers["Content-Type"] = "image/png";
  response.bodyFilePath = "~/Desktop/image.png";
 
  // Done
  return response;
}

function onResponse(context, url, request, response) {
 
  response.headers["Content-Type"] = "application/json";
  response.bodyFilePath = "~/Desktop/my_response.json";
 
  // Done
  return response;
}

Use JSON File as a Body of Request or Response

It's possible to use your JSON file and set it as a Request/Response's body

Please follow this tutorial.

Use multiple JSON files

You can use set a different body for each matching endpoint by using the IF statement.

Follow this tutorial to understand how to import a JSON file to the script
Set Script Rule with wildcard or Regex pattern that can match many endpoints. E.g https://my-domain.com/v\*
Use `includes()` to check whether or not the endpoint is matched

const file_1 = require("@users/myfile_1.json");
const file_�2 = require("@users/myfile_2.json");
const file_3 = require("@users/myfile_3.json");

function onResponse(context, url, request, response) {
  
  // Set JSON content
  response.headers["Content-Type"] = "application/json";
  
  // Check
  if (url.includes("v1/data")) {
    response.body = file_1
  } else if (url.includes("v2/login")) {
      response.body = file_2
  } else if (url.includes("v3/user")) {
      response.body = file_3
  }

  // Done
  return response;
}

Map Local with GraphQL

// Import your JSON file here 
const file = require("@users/B02D96D5.default_message_32E64A5B.json");

function onRequest(context, url, request) {

  // 1. Extract the queryName from the request
  var queryName = request.body.query.match(/\S+/gi)[1].split('(').shift();

  // 2. Save to sharedState
  sharedState.queryName = queryName

  // Done
  return request;
}

function onResponse(context, url, request, response) {

  // 3. Check if it's the request we need to map
  if (sharedState.queryName == "user") {
    
    // 4. Import the local file by Action Button -> Import
    // Get the local JSON file and set it as a body (like Map Local)
    response.headers["Content-Type"] = "application/json";
    response.body = file;
  }

  // Done
  return response;
}

Use ArrayBuffer in Request/Response Body

Since Javascript doesn't have the Data object type, the Data Body will convert to Base64 Encoded String in Javascript. To pass Uint8Array, blob, or ArrayBuffer to the body, make sure you convert to Base64 Encoded String and set the ContentType to application/octet-stream

Proxyman will convert Base64 Encoding to ArrayBuffer, so the client will receive the data properly.

// Import
const { btoa } = require('@addons/Base64.js');

function onResponse(context, url, request, response) {
  // Construct the ArrayBuffer
  const buffer = new ArrayBuffer(256)
  const view = new Uint8Array(buffer)
  for (let i = 0; i < view.length; i++) {
    view[i] = i
  }
  
  // Convert ArrayBuffer to Base64String
  var newBody = btoa(String.fromCharCode.apply(null, new Uint8Array(buffer)));
  
  // Set new body
  response.body = newBody;
  response.statusCode = 200
  response.headers['Content-Type'] = 'application/octet-stream'

  // Done
  return response;
}

Preserve the Host

function onRequest(context, url, request) {
    request.preserveHostHeader = true
    return request
}

Comment & Highlight with color

Use comment or color to highlight on the main table view.

function onRequest(context, url, request) {
    request.comment = "It's a Request"
    request.color = "red" // red, blue, yellow, purple, gray, green
    return request
}

function onResponse(context, url, request, response) {
    response.comment = "It's a Response"
    response.color = "yellow" // red, blue, yellow, purple, gray, green
    return response
}

Import Files with require()

JSON

Prepare a JSON file and save it to your Desktop

// myfile.json
{
  "name": "Proxyman",
  "platform": "macOS",
  "info": {
    "website": "proxyman.io",
    "region": "Earth"
  }
}

2. More -> Import JSON or Other Files. Then selecting your file

3. Proxyman will add the import code to the top of the script

// ~/Library/Application Support/com.proxyman.NSProxy/users/myfile.json
const file = require("@users/myfile.json");

function onResponse(context, url, request, response) {
  // 1. Set header to JSON if need
  response.headers["Content-Type"] = "application/json";

  // 2. Set Body as a imported file
  response.body = file;
  
  return response;
}

{% hint style="info" %} The selected file is copied to ~/Library/Application\ Support/com.proxyman.NSProxy/users folder. {% endhint %}

{% hint style="info" %} To support other format files, such as image, text, pdf. Make sure you have correct Header Content-Type {% endhint %}

Binary File

Follow the same above instruction (Select your Binary File)
Set it as a body

// ~/Library/Application Support/com.proxyman.NSProxy/users/myscreenshot.png
const file = require("@users/myscreenshot.png");

function onResponse(context, url, request, response) {
  // Set header
  response.headers["Content-Type"] = "image/png";

  // Set Body
  response.body = file;
  
  return response;
}

Text-Based File

Follow the same above instruction (Select your Binary File)
Set it as a body

// ~/Library/Application Support/com.proxyman.NSProxy/users/main.css
const file = require("@users/main.css");

function onResponse(context, url, request, response) {
  // Set header
  response.headers["Content-Type"] = "text/css";

  // Set Body
  response.body = file;
  
  return response;
}

Import File without using the "Import Tool"

From Proxyman 2.24.0+, you can import any files without using the "Import File".

// Import your file from your Desktop folder
const file = require("~/Desktop/myfile.json");

function onResponse(context, url, request, response) {

  // 1. Set header to JSON if need
  response.headers["Content-Type"] = "application/json";

  // 2. Set Body as a imported file
  response.body = file;
  
  return response;
}

If the file has ".js" as an extension => Proxyman will execute it as a JS Script
Otherwise, Proxyman will import it as normal

{% hint style="info" %} Only files that are imported by using the "Import Tool", are included when exporting the script to your colleague. {% endhint %}

Use as Mock API

You can use Scripting as a Mock API by following this guideline.

Using Addons

Full list of built-in addons

Use Base64 Addon

// Encode Base64
const { btoa } = require("@addons/Base64.js")

// Usage:
var text = "HelloWorld";
var encodedText = btoa(text);

// Decode Base64
const { atob } = require("@addons/Base64.js")

// Usage:
var text = atob("aGVsbG8=");

Use Hashing Addon (MD5, SHA1, SHA256, SHA512)

// Hash MD5
const { md5 } = require("@addons/MD5.js")

// Usage:
var hashedText = md5("Hello World");

// Hash SHA1
const { sha1 } = require("@addons/SHA1.js")

// Usage:
var hashedText = sha1("Hello World");

Use UUID-v4 Addon

// Hash MD5
const { uuidv4 } = require("@addons/UUID.js")

// Usage:
var uuid = uuidv4();

Deflate/Inflate and GZip/UnGZip

Deflate/inflate

const { inflate, deflate } = require("@addons/Pako.js")

// Compress
var input = "Hello World from Pako!!!"
var result = deflate(input);
console.log(result); // eJzzSM3JyVcIzy/KSVFIK8rPVQhIzM5XVFQEAGsMB/8=

// Decompress
var text = 'eJzzSM3JyVcIzy/KSVFIK8rPVQhIzM5XVFQEAGsMB/8=';
var rawText = inflate(text);
console.log(rawText); // Hello World from Pako!!!

GZip/UnGZip

const { ungzip, gzip } = require("@addons/Pako.js")

// Compress
var text =  'HelloWorld';
var result = gzip(text);
console.log(result); // H4sIAAAAAAAAA/NIzcnJD88vykkBAHkMd3cKAAAA

// Decompress
var text =  'H4sIAAAAAAAAA/NIzcnJD88vykkBAHkMd3cKAAAA';
var rawText = ungzip(text);
console.log(rawText); // HelloWorld

JWT Decode

const { jwtDecode } = require('@addons/JWTDecode.js');

var text = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c';
var jSONObject = jwtDecode(text)

Logging

// Print the obj
const myObj = {};
console.log(myObj);

// Print type of the obj
console.log(typeof(myObj));

Regex

Only number

//Init Regex
var reg = /^-?\d*\.?\d*$/;

if (reg.test("123123123")) {
    console.log("Matched");
}

Regex to get the Scheme, Host, Port, Path, and Query of the URL

function onRequest(context, url, request) {
  console.log(url);

  // Get each part
  const regex = /^(https?):\/\/([^:\/\n]+)(?::(\d+))?([^#\n?]+)(?:\?([^#\n]+))?/;
  const [, scheme, host, port, path, query] = url.match(regex);

  // Assign again
  request.scheme = scheme;
  request.host = host;
  if (port !== undefined) {
    request.port = parseInt(port);
  }
  request.path = path;

  // Log
  console.log("----------");
  console.log(scheme);
  console.log(host);
  console.log(port);
  console.log(path);

  // Done
  return request;
}

Miscellaneous

By-pass CORS

function onResponse(context, url, request, response) {  

  // Allow all
  response.headers["Access-Control-Allow-Origin"] = "*";
  response.headers["Access-Control-Allow-Headers"] = "*"；
  response.headers["Access-Control-Allow-Methods"] = "*";

  // Done
  return response;
}

Inject Header to Request / Response

function onRequest(context, url, request) {
  // add header
  request.headers["My-Injected-Header"] = "Proxyman";
  return request
}

function onResponse(context, url, request, response) {    
  // add header
  response.headers["My-Injected-Header"] = "Proxyman";
  return response;
}

Response delay with sleep() function

the It's useful for simulating the "Slow Network" on a particular Request or Response. You can check out the Network Conditions tool for GUI.

macOS

function onResponse(context, url, request, response) {
  console.log("Start sleep");
  
  // Sleep 5 seconds
  sleep(5000);
  
  // Done
  return response;
}

Windows/Linux

async function onResponse(context, url, request, response) {
  console.log("Start sleep");
  
  // Sleep 5 seconds
  // Must use `await` keyword on Windows/Linux
  await sleep(5000);
  
  // Done
  return response;
}

AES Encryption/Decryption

const { encryptAES, decryptAES } = require("@addons/CryptoJS.js")

function onRequest(context, url, request) {
  
  // Encrypt
  var message = 'my message from Proxyman';
  var password = 'secret key 123';
  var ciphertext = encryptAES(message, password);
  
  // Decrypt
  var originalText = decryptAES(ciphertext, password);

  // Done
  return request;
}

DES Encryption/Decryption

const { encryptDES, decryptDES } = require("@addons/CryptoJS.js")

function onRequest(context, url, request) {
  
  // Encrypt
  var message = 'my message from Proxyman';
  var password = 'secret key 123';
  var ciphertext = encryptDES(message, password);
  
  // Decrypt
  var originalText = decryptDES(ciphertext, password);

  // Done
  return request;
}

Write / Export to a local file

Override Mode

function onResponse(context, url, request, response) {

  // Write to single file
  writeToFile(response.body, "~/Desktop/body.json");
  
  // Write the Body to file with flow ID
  writeToFile(response.body, "~/Desktop/sample-" + context.flow.id);
  
  // Done
  return response;
}

Append Mode (Only for Proxyman 3.6.2+)

async function onResponse(context, url, request, response) {

  // Append to the existed file
  // Or create a new file if it doesn't exist
  var opt = {appendFile: true}
  writeToFile(response.body, "~/Desktop/body.json", opt);

  // Done
  return response;
}

Check if the first exist

Available: Proxyman macOS 5.4.0+

async function onRequest(context, url, request) {

  const filePath = "~/Desktop/myfile.json"
  
  // check if the file exists
  if (isFileExists(filePath)) {
    console.log("File exists");
  } else {
    console.log("File NOT exists");  
  }
  
  // Done
  return request;
}

Read a file

If it's text-based -> Return a String
Otherwise -> Return Uint8Array
Available: Proxyman macOS 5.4.0+

async function onRequest(context, url, request) {  // console.log(request);

  const textFilePath = "~/Desktop/myfile.json";
  
  // check exist
  if (isFileExists(filePath)) {
  
    // read from file
    const text = readFromFile(textFilePath);
    
    // pares string to JSON Object
    const obj = JSON.parse(text);
  }
  
  // Read binary file
  const binaryFilePath = "~/Desktop/screenshot.png";
  const binaryFile = readFromFile(binaryFilePath); // Uint8Array
  
  // Done
  return request;
}

Map Remotes

Map v1 to v2 endpoints

function onRequest(context, url, request) {
  
  // Replace v1 to v2 in URL Path
  var newPath = request.path.replace("v1", "v2");
  request.path = newPath

  // Done
  return request;
}

Map localhost to production

function onRequest(context, url, request) {
  
  // Use production URL
  request.scheme = "https";
  request.host = "proxyman.io";
  request.port = 443;

  // Done
  return request;
}

Map production to localhost

function onRequest(context, url, request) {
  
  // Use production URL
  request.scheme = "http";
  request.host = "localhost";
  request.port = 3000;

  // Done
  return request;
}

Make async/await HTTP Request (macOS)

{% hint style="info" %} This feature `$http` is available on the macOS version. To use on Windows, please check the next part. {% endhint %}

GET Request with Query

async function onResponse(context, url, request, response) {  
  // GET Request with Query
  var url = "https://httpbin.proxyman.app/get?id=proxyman&country=united%20states";
  var output = await $http.get(url);
  
  // Get Status Code
  console.log(output.statusCode);
  
  // Get body
  console.log(output.body)
  
  // Get header
  console.log(output.headers)
  
  // Done
  return response;
}

POST Request with JSON Body

async function onResponse(context, url, request, response) {  
  // Define JSON Body and Header
  // Make sure "Content-Type" is "application/json"
  var param = {
    body: {
      "user": {
        "name": "Proxyman"
      }
    },
    headers: {
      "Content-Type": "application/json"
    }
  }

  // POST request with await
  var output = await $http.post("https://httpbin.proxyman.app/post", param);
  
  // Get Status Code
  console.log(output.statusCode);
  
  // Get body
  console.log(output.body)
  
  // Get header
  console.log(output.headers)
  
  // Done
  return response;
}

POST Request with application/x-www-form-urlencoded body

async function onResponse(context, url, request, response) {  
  // Define form Body and Header
  // Make sure "Content-Type" is "application/x-www-form-urlencoded"
  var param = {
    body: {
      "key1": "value1",
      "key2": "value2"
    },
    headers: {
      "Content-Type": "application/x-www-form-urlencoded"
    }
  }

  // POST request with await
  var output = await $http.post("https://httpbin.proxyman.app/post", param);
  
  // Get Status Code
  console.log(output.statusCode);
  
  // Get body
  console.log(output.body)
  
  // Get header
  console.log(output.headers)
  
  // Done
  return response;
}

PUT / PATCH / DELETE Request

async function onRequest(context, url, request) {  

  var param = {
    body: {
      "user": {
        "name": "Proxyman"
      }
    },
    headers: {
      "Content-Type": "application/json"
  }


  var output = await $http.post("https://httpbin.proxyman.app/post", param);
  var output = await $http.put("https://httpbin.proxyman.app/put", param);
  var output = await $http.delete("https://httpbin.proxyman.app/delete", param);
  
  // Done
  return request;
}

Make async/await HTTP Request (Windows/Linux)

Windows/Linux ships with a built-in Axios library. You can easily make HTTP(s) requests with `Axios` syntax.

async function getUser() {
  try {
    const response = await axios.get('https://httpbin.proxyman.app/user?ID=12345');
    console.log(response);
  } catch (error) {
    console.error(error);
  }
}

Abort the request/response like Block List Tool

Only available for Proxyman 3.11.0 and later

Abort the request

function onRequest(context, url, request) {
  // drop the connection
  abort();
}

function onRequest(context, url, request) {

  // Use the if to abort on certain conditions
  if (true) {
    abort();
    return; // Must return a void to stop the func
  }

  // Done
  return request;
}

Abort the response

function onResponse(context, url, request, response) {    
  // drop the connection
  abort();
}

URL and URLSearchParams

From Proxyman 4.13.0 or later, URL and URLSearchParams are natively supported.

function onRequest(context, url, request) {

  // URL
  const urlObj = new URL("https://proxyman.io/api/v1/user?id=123");
  console.log(urlObj.hostname);
  console.log(urlObj.search);
  console.log(urlObj.searchParams);

  // URLSearchParmas
  const params1 = new URLSearchParams("foo=1&bar=2");
  
  // Done
  return request;
}

Reload System Environment Variables

Proxyman macOS 4.15.0 or later.

Make sure we enable the permission first, in the More Button -> Environment Variables -> Allow all scripts to read env.

async function onRequest(context, url, request) {
  // manually reload to get the latest changes
  _reloadEnv();
  
  // get env
  console.log($PROXYMAN_ID)
  
  // Done
  return request;
}

Change Websocket URL, Requests/Response Header

Supported from Proxyman 6.2.0 or later for macOS.
onRequest and onResponse modify the URL and handshake headers. Message payloads cannot be modified; use onWebsocket to inspect and log them on macOS Proxyman 26.1.0 or later.

Map from localhost to production

Rule ws://proxyman.debug:3000

async function onRequest(context, url, request) {
  // console.log(request);
  console.log(url);

  request.scheme = "wss";
  request.host = "wss.httpbin-proxyman.xyz"
  request.port = 443

  // Done
  return request;
}

Production to localhost

Rule wss://echo.websocket.org

async function onRequest(context, url, request) {
  // console.log(request);
  console.log(url);

  request.scheme = "ws";
  request.host = "proxyman.debug"
  request.port = 3000

  // Done
  return request;
}

Log WebSocket messages with onWebsocket

{% hint style="warning" %} These onWebsocket snippets require macOS Proxyman 26.1.0 or later. They are not available on Windows, Linux, or iOS. {% endhint %}

Match the captured ws:// or wss:// URL, save and activate the script, then reconnect the WebSocket. See Scripting with WebSocket for setup and the complete message object.

Each example defines a separate onWebsocket function. Use one example, or combine the checks into a single function. The hook is read-only: changing message or returning a value does not modify traffic.

Log every captured message from both sides:

function onWebsocket(context, url, request, response, message) {
  console.log(`[${message.from}] ${message.type}: ${message.data}`);
}

Read text and JSON messages

Inspect text sent by the server. JSON messages are parsed when valid; other text is logged unchanged.

function onWebsocket(context, url, request, response, message) {
  if (message.type !== "text" || message.from !== "server") return;

  try {
    const payload = JSON.parse(message.data);
    console.log("Server JSON: " + JSON.stringify(payload, null, 2));
  } catch (error) {
    // A text message does not have to contain JSON.
    console.log("Server text: " + message.data);
  }
}

Proxyman reassembles fragmented text frames before calling the hook, so you can parse the complete JSON message here. Binary fragments are also reassembled; there is no separate continuation-frame callback.

Inspect binary messages

Use message.rawData for the original bytes. message.data is only a text representation and may be Binary (length=N).

function onWebsocket(context, url, request, response, message) {
  if (message.type !== "binary") return;

  const bytes = message.rawData;
  // Limit the preview so large messages do not flood the console.
  const hex = Array.from(bytes.slice(0, 32))
    .map(byte => byte.toString(16).padStart(2, "0"))
    .join(" ");
  const suffix = bytes.length > 32 ? " ..." : "";
  console.log(`[${message.from}] binary (${bytes.length} bytes): ${hex}${suffix}`);
}

rawData is a copied Uint8Array and is non-enumerable. Access it directly rather than expecting console.log(message) or JSON.stringify(message) to include it.

Log ping and pong frames

Use these events to inspect heartbeat traffic in either direction. Ping and pong payloads are not exposed.

function onWebsocket(context, url, request, response, message) {
  if (message.type !== "ping" && message.type !== "pong") return;

  console.log(`[${message.from}] ${message.type} on ${url}`);
}

Inspect close frames

Log the close code and which side sent the frame. The close reason is not exposed.

function onWebsocket(context, url, request, response, message) {
  if (message.type !== "close") return;

  console.log(`[${message.from}] closed with code ${message.closeCode}`);
}

Use `npm install`

Install a package

Open Terminal and install packages into Proxyman's Application Support folder:

Install dayjs

$ cd "$HOME/Library/Application Support/com.proxyman.NSProxy"
$ npm install --prefix . dayjs --ignore-scripts --no-audit --no-fund

After installation, the package should exist in:

~/Library/Application Support/com.proxyman.NSProxy/node_modules

Use a package in a script

Use the package name with require():

const dayjs = require("dayjs");

async function onRequest(context, url, request) {
  const formattedDate = dayjs("2026-05-05T13:00:00Z").format("YYYY-MM-DD");
  request.headers["X-Proxyman-Dayjs"] = formattedDate;
  return request;
}

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Snippet Code

1. What's it?

2. Common on Request and Response

Multipart/form-data

3. Addons

3.1 Use `npm install`

4. Regex

5. Import / Export Files

6. Miscellaneous

7. Encryption/Decryption

8. Map Remote with Scripting

9. Make Async/await HTTP Request (macOS)

9.1. Make Async/await HTTP Request (Windows/Linux)

10. URL and URLSearchParams

11. Access Environment Variables

12. Websocket

HTTP Header

Add/Update: Request or Response Header

Delete: Request or Response Header

Request Query

Add/Update

Delete

URLEncoded Form Body

Add/Update

Delete

Change Request Destination (scheme, host, port, path)

Upstream ALPN and HTTP/2 settings

HTTP to HTTPS

HTTPS to HTTP

Change HTTP Request Method

Change Response HTTP Status Code

JSON Body

On Request

On Response

Multipart/form-data

Map a local file to Response's Body like Map Local Tool (Proxyman 2.25.0+)

Use JSON File as a Body of Request or Response

Use multiple JSON files

Map Local with GraphQL

Use ArrayBuffer in Request/Response Body

Preserve the Host

Comment & Highlight with color

Import Files with require()

JSON

Binary File

Text-Based File

Import File without using the "Import Tool"

Use as Mock API

Using Addons

Use Base64 Addon

Use Hashing Addon (MD5, SHA1, SHA256, SHA512)

Use UUID-v4 Addon

Deflate/Inflate and GZip/UnGZip

Deflate/inflate

GZip/UnGZip

JWT Decode

Logging

Regex

Only number

Regex to get the Scheme, Host, Port, Path, and Query of the URL

Miscellaneous

By-pass CORS

Inject Header to Request / Response

Response delay with sleep() function

AES Encryption/Decryption

DES Encryption/Decryption

Write / Export to a local file

Check if the first exist

Read a file

Map Remotes

Map v1 to v2 endpoints

Map localhost to production

Map production to localhost

Make async/await HTTP Request (macOS)