GM APIs Reference

Complete reference for all Greasemonkey APIs supported by CodeTweak with practical examples and best practices.

Remember: You must enable each GM API in the script editor's "GM API Access" section before using it in your code.

Storage & Data APIs

GM_setValue

Storage

Stores a value that persists across page loads and browser sessions.

GM_setValue('key', value)

Parameter	Type	Description
key	string	Unique identifier for the stored value
value	any	Value to store (string, number, boolean, object)

Example Usage:

// Store different types of data
GM_setValue('username', 'john_doe');
GM_setValue('score', 1250);
GM_setValue('settings', {theme: 'dark', notifications: true});
GM_setValue('lastVisit', new Date().toISOString());

GM_getValue

Storage

Retrieves a previously stored value, with optional default fallback.

GM_getValue('key', defaultValue)

Parameter	Type	Description
key	string	Key of the value to retrieve
defaultValue	any	Value returned if key doesn't exist

Example Usage:

// Get stored values with defaults
const username = GM_getValue('username', 'anonymous');
const score = GM_getValue('score', 0);
const settings = GM_getValue('settings', {theme: 'light'});

// Use the retrieved values
console.log(`Welcome back, ${username}! Your score: ${score}`);

GM_deleteValue

Storage

Removes a stored value permanently.

GM_deleteValue('key')

Example Usage:

// Clear user data
GM_deleteValue('username');
GM_deleteValue('score');

// Clear all data on reset
function resetUserData() {
    GM_deleteValue('settings');
    GM_deleteValue('resetRequested');
}

GM_listValues

Storage

Returns an array of all stored keys for this script.

GM_listValues()

Example Usage:

// List all stored keys
const keys = GM_listValues();
console.log('Stored keys:', keys);

// Export all data
const exportData = {};
keys.forEach(key => {
    exportData[key] = GM_getValue(key);
});
console.log('Export data:', exportData);

Browser & UI APIs

GM_openInTab

Browser

Opens a URL in a new browser tab with optional configuration.

GM_openInTab(url, options)

Parameter	Type	Description
url	string	URL to open
options	object	Configuration object (optional)
options.active	boolean	Whether to focus the new tab

Example Usage:

// Open in background tab
GM_openInTab('https://example.com', {active: false});

// Open in focused tab
GM_openInTab('https://github.com', {active: true});

// Simple usage
GM_openInTab('https://google.com');

GM_notification

Displays a desktop notification to the user.

GM_notification(options)

Parameter	Type	Description
options.text	string	Notification message
options.title	string	Notification title (optional)
options.image	string	Icon URL (optional)
options.onclick	function	Click handler (optional)

Example Usage:

// Simple notification
GM_notification({
    text: 'Script executed successfully!',
    title: 'CodeTweak'
});

// Advanced notification with callback
GM_notification({
    text: 'New message received',
    title: 'Chat App',
    image: 'https://example.com/icon.png',
    onclick: function() {
        window.focus();
        console.log('Notification clicked');
    }
});

GM_addStyle

Injects CSS styles into the current page.

GM_addStyle(css)

Example Usage:

// Add custom styles
GM_addStyle(`
    .my-custom-class {
        background: #f0f0f0;
        padding: 10px;
        border-radius: 5px;
    }
    .highlight {
        background: yellow;
        font-weight: bold;
    }
`);

// Apply styles to existing elements
document.querySelectorAll('.important').forEach(el => {
    el.classList.add('highlight');
});

GM_addElement

Creates and appends a new DOM element with specified attributes.

GM_addElement(parent, tag, attributes)

Parameter	Type	Description
parent	Element	Parent element to append to
tag	string	HTML tag name
attributes	object	Element attributes (optional)

Example Usage:

// Add a button to the page
const button = GM_addElement(document.body, 'button', {
    textContent: 'Click Me!',
    onclick: () => alert('Button clicked!')
});

// Add a styled container
const container = GM_addElement(document.body, 'div', {
    id: 'my-container',
    style: 'position: fixed; top: 10px; right: 10px; z-index: 9999;'
});

Network & Resources APIs

GM_xmlhttpRequest

Network

Makes cross-origin HTTP requests that bypass CORS restrictions.

GM_xmlhttpRequest(options)

Parameter	Type	Description
options.method	string	HTTP method (GET, POST, etc.)
options.url	string	Request URL
options.headers	object	Request headers (optional)
options.data	string	Request body (optional)
options.onload	function	Success callback
options.onerror	function	Error callback

Example Usage:

// GET request
GM_xmlhttpRequest({
    method: 'GET',
    url: 'https://api.example.com/data',
    headers: {
        'User-Agent': 'CodeTweak Script',
        'Accept': 'application/json'
    },
    onload: function(response) {
        console.log('Status:', response.status);
        console.log('Response:', response.responseText);
    }
});

// POST request with data
GM_xmlhttpRequest({
    method: 'POST',
    url: 'https://api.example.com/submit',
    headers: {
        'Content-Type': 'application/json'
    },
    data: JSON.stringify({message: 'Hello World'}),
    onload: function(response) {
        console.log('Response:', response.responseText);
    }
});

GM_getResourceText

Resources

Retrieves the content of a bundled resource as text.

GM_getResourceText('resourceName')

Setup Required: Resources must be defined in the editor's "Script Resources" section before use.

Example Usage:

// Get CSS resource and inject it
const customCSS = GM_getResourceText('myStyles');
GM_addStyle(customCSS);

// Get JSON config file
const configText = GM_getResourceText('config');
const config = JSON.parse(configText);
console.log('Config loaded:', config);

GM_setClipboard

System

Copies text to the system clipboard.

GM_setClipboard(text, type)

Parameter	Type	Description
text	string	Text to copy to clipboard
type	string	MIME type (optional, defaults to 'text/plain')

Example Usage:

// Copy simple text
GM_setClipboard('Hello, World!');

// Copy formatted data
const data = {name: 'John', age: 30};
GM_setClipboard(JSON.stringify(data, null, 2));

// Copy with specific MIME type
GM_setClipboard('Hello
', 'text/html');

Security Notes:

Validate data from GM_getValue before use
Be cautious with GM_xmlhttpRequest to untrusted URLs
Sanitize content before using GM_addStyle or GM_addElement

Script Editor Advanced Features