Chrome 135 Extension Changes: What Developers Need to Know

Chrome 135 introduces game-changing APIs for extension developers: userScripts.execute() for dynamic script injection, chrome.storage integration directly in DevTools, and trial tokens for Origin Trials. These updates accelerate the shift toward AI-powered agents and Manifest V3 compliance.

What’s New in Chrome 135

Chrome finally delivers runtime script injection without pre-declaring in manifest.json:

chrome.userScripts.execute({
  target: { tabId: 123 },
  files: ['agent.js'],
  runAt: 'document_idle'
});

chrome.userScripts.execute({
  target: { tabId: 123 },
  files: ['agent.js'],
  runAt: 'document_idle'
});

Impact: AI agents can now adapt to page content without reloads — perfect for form-filling, price scraping, dynamic analysis.

No more console.log debugging — inspect extension storage directly:

DevTools → Application → Storage → Extension Storage
→ Live view of chrome.storage.local/sync
→ Edit values on-the-fly

DevTools → Application → Storage → Extension Storage
→ Live view of chrome.storage.local/sync
→ Edit values on-the-fly

Impact on Extension Categories

86% of extensions still use MV2 — Chrome 135 accelerates the June 2025 killswitch.

What Firefox & Edge Are Doing

Firefox: Mandatory Data Disclosure

Starting November 3, 2025, Firefox enforces a new mandatory data disclosure policy for all new browser extensions submitted to their Add-ons Marketplace. This policy requires developers to explicitly declare if and how their extension collects user data directly within the extension’s manifest file. It aims to increase transparency and user trust by providing clear, upfront information about data collection practices before installation.

Extensions must specify what types of personal or usage data they collect, how that data will be used, and whether it is shared with third parties. Failure to comply with these requirements will result in the rejection of the extension during the review process. This move aligns Firefox with global privacy trends and regulatory frameworks, ensuring users have better control and awareness over their data while using extensions. Developers planning releases or updates must prepare to update their manifests accordingly and clearly communicate data practices to avoid delays or denials in publishing.

Manifest:

{
  "browser_specific_settings": {
    "gecko": {
      "data_collection_permissions": {
        "collects_data": true,
        "data_types": ["browsing_history"]
      }
    }
  }
}

{
  "browser_specific_settings": {
    "gecko": {
      "data_collection_permissions": {
        "collects_data": true,
        "data_types": ["browsing_history"]
      }
    }
  }
}

Deadline: Q1 2026 for existing extensions.​

Edge: Copilot Integration

Microsoft Edge has integrated Copilot, an AI-powered assistant designed to enhance productivity for enterprise users. Copilot is accessible through a native sidebar within Edge, allowing users to perform context-aware tasks like searching, summarizing pages, or managing tabs without leaving their browsing session.

This integration emphasizes seamless AI assistance inside the browser, focusing primarily on enterprise scenarios with IT administrator controls. Microsoft officially announced Copilot Mode as part of Edge’s AI-driven browsing experience in July 2025, highlighting natural voice navigation, multitasking support, and privacy-first design.

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