1. Inject script into process on host via REPL

    Injecting a Frida instrumentation script on the host machine can be achieved through the following command. Here the -n switch specifies the process name to attach to.

    $ frida -n Twitter -l demo1.js

  2. List all running process names and PIDs

    The following command lists all the running processes in a tabular format with name and PID columns.

    $ frida-ps

  3. List all running process names on a USB device

    The following command lists all the running processes on a USB device in a tabular format with name and PID columns. The -U specifies that a USB device is being queried.

    $ frida-ps -Uai

  4. List all attached devices

    The following command lists all the attached devices. Processes on these devices can be instrumented by Frida.

    $ frida-ls-devices

  5. Tracing native APIs

    The following command can be used to trace a native API in a specific process. Function names can be specified using wildcard characters (as shown below), which can be particularly useful while exploring or discovering user-defined functions within the process.

    1. $ frida-trace -n Twitter -i "*URL*"$
    2. $ frida-trace -U Twitter -i "*URL*"$ // USB Device
  6. Tracing Objective-C APIs

    The following command can be used to trace an Objective-C API in a specific process. Notice the difference in switch, in this case it’s -m instead of -i. Objective-C APIs names, the Class names as well as the method types (class method or instance method) can all be specified using wildcard characters (as shown below). This can be particularly useful while exploring or discovering user-defined methods within a process.

    $ frida-trace -U Twitter -m "-[NSURL* *HTTP*]"

  7. Backtracing an Objective-C method call

    The following command can be used to generate a backtrace for an Objective-C method call in a specific process.

    Tip: Add the following code to the onEnter event-handler in the auto-generated JS of the desired API

    log('\tBacktrace:\n\t' + Thread.backtrace(this.context, Backtracer.ACCURATE).map(DebugSymbol.fromAddress) .join('\n\t'));

  8. Writing data to file

    If you want to write some data to a file, you should send() it from the injected script and receive it in your Frida-based application, where you then write it to a file.

    Tip: The data that you send() should be JSON serializable.


     var data = { foo: 'bar' };

     import frida
     def on_message(message, data):
  9. Calling a native function

    var address = Module.findExportByName('libsqlite3.dylib', 'sqlite3_sql');
    var sql = new NativeFunction(address, 'char', ['pointer']);

Explanation here.

Data Structures

Tip: If things don’t seem to be working as expected you may be interacting with the wrong data type - run console.log("Type of args[2] -> " + new ObjC.Object(args[2]).$className) to determine the actual type of the object that you’re dealing with!

  1. Converting NSData to String

    var data = new ObjC.Object(args[2]);
    Memory.readUtf8String(data.bytes(), data.length());

    Tip: 2nd argument (number of bytes) is not required if the string data is null-terminated.

  2. Converting NSData to Binary Data

    var data = new ObjC.Object(args[2]);
    Memory.readByteArray(data.bytes(), data.length());
  3. Iterating an NSArray

    ``` var array = new ObjC.Object(args[2]); /*

    • Be sure to use valueOf() as NSUInteger is a Number in
    • 32-bit processes, and UInt64 in 64-bit processes. This
    • coerces it into a Number in the latter case. */ var count = array.count().valueOf(); for (var i = 0; i !== count; i++) { var element = array.objectAtIndex_(i); } ```
  4. Iterating an NSDictionary

    var dict = new ObjC.Object(args[2]);
    var enumerator = dict.keyEnumerator();
    var key;
    while ((key = enumerator.nextObject()) !== null) {
      var value = dict.objectForKey_(key);
  5. Unarchiving an NSKeyedArchiver

    var parsedValue = ObjC.classes.NSKeyedUnarchiver.unarchiveObjectWithData_(value);
  6. Reading a struct

    If args[0] is a pointer to a struct, and let’s say you want to read the uint32 at offset 4, you can do it as shown below: Memory.readU32(args[0].add(4));

Objective-C examples

Displaying an alert box on iOS 7

var UIAlertView = ObjC.classes.UIAlertView; /* iOS 7 */
var view = UIAlertView.alloc().initWithTitle_message_delegate_cancelButtonTitle_otherButtonTitles_(
    'Hello from Frida',

Displaying an alert box on iOS >= 8

This is an implementation of the following code.

// Defining a Block that will be passed as handler parameter to +[UIAlertAction actionWithTitle:style:handler:]
var handler = new ObjC.Block({
  retType: 'void',
  argTypes: ['object'],
  implementation: function () {

// Import ObjC classes
var UIAlertController = ObjC.classes.UIAlertController;
var UIAlertAction = ObjC.classes.UIAlertAction;
var UIApplication = ObjC.classes.UIApplication;

// Using Grand Central Dispatch to pass messages (invoke methods) in application's main thread
ObjC.schedule(ObjC.mainQueue, function () {
  // Using integer numerals for preferredStyle which is of type enum UIAlertControllerStyle
  var alert = UIAlertController.alertControllerWithTitle_message_preferredStyle_('Frida', 'Hello from Frida', 1);
  // Again using integer numeral for style parameter that is enum
  var defaultAction = UIAlertAction.actionWithTitle_style_handler_('OK', 0, handler);
  // Instead of using `ObjC.choose()` and looking for UIViewController instances
  // on the heap, we have direct access through UIApplication:
  UIApplication.sharedApplication().keyWindow().rootViewController().presentViewController_animated_completion_(alert, true, NULL);

Printing an NSURL argument

The following code shows how you can intercept a call to [UIApplication openURL:] and display the NSURL that is passed.

// Get a reference to the openURL selector
var openURL = ObjC.classes.UIApplication["- openURL:"];

// Intercept the method
Interceptor.attach(openURL.implementation, {
  onEnter: function(args) {
    // As this is an ObjectiveC method, the arguments are as follows:
    // 0. 'self'
    // 1. The selector (openURL:)
    // 2. The first argument to the openURL selector
    var myNSURL = new ObjC.Object(args[2]);
    // Convert it to a JS string
    var myJSURL = myNSURL.absoluteString().toString();
    // Log it
    console.log("Launching URL: " + myJSURL);