Everything that happened with Chrome Extensions in 2025

Chrome Extensions Platform & Web Store – 2025 Year in Review

Key Concepts:

• Manifest V3: The latest manifest version for Chrome extensions, now fully transitioned to.
• Chrome.sto API: An extension API for storing data.
• User Scripts API: Allows execution of arbitrary code provided by users.
• WebMCP & MCP: Technologies expected to mature and influence future extension capabilities (Machine Learning Compilation Pipeline & Web Machine Compilation Pipeline).
• WXT: A library simplifying Chrome extension development.
• Puppeteer: A Node library providing a high-level API to control Chrome or Chromium over the DevTools Protocol.
• Chrome Web Store API: New API for interacting with the Chrome Web Store programmatically.
• Browser Namespace: An alternative to accessing extension APIs via the window.chrome global.
• Side Panel API: API for creating side panels within the browser.
• Google Summer of Code: A program allowing students to contribute to Chromium development.

I. Overall 2025 Trends & Themes

2025 marked the completion of the transition to Manifest V3 for Chrome extensions. Significant platform API additions were launched in Chrome, alongside new capabilities within the Chrome Web Store. A dominant theme throughout the year was the exploration of Artificial Intelligence (AI) within extensions, with developers experimenting with agentic capabilities (extensions driving browser actions) and integrating AI functionality into existing features like tab groups. The speaker anticipates continued experimentation as technologies like MCP and WebMCP mature. Community contributions, particularly libraries like WXT, have also been crucial to the platform’s growth.

II. Month-by-Month Breakdown of Key Updates

• January: Introduction of a new DevTools feature enabling visibility of data stored via the Chrome.sto extension API. This feature was highly requested, being the fourth most starred issue in DevTools.
• February: Support added for creating multiple worlds within the User Scripts API – a niche but important update.
• March: Launch of the userScripts.execute API, a frequently requested feature allowing immediate execution of user-provided code under specific conditions. The ability to cancel pending submissions in the Chrome Web Store was also launched, providing developers with greater control over their updates.
• April: Updates to the Puppeteer testing library simplified extension loading, leveraging a new standard for browser testing offering broader capabilities than its predecessor. This new standard is built on top of WebDriver.
• May: Google I/O showcased significant developments, with David Hafsa and Sebastian providing detailed overviews (videos available for separate viewing).
• June: Changes to user granting of access to the User Scripts API were implemented. A global developer mode toggle was replaced with individual toggles for each extension, based on community feedback. Built-in AI APIs (prompt API, summarizer, translator, language detector) reached stable status in Chrome 138, accessible without flags or origin trials. Comprehensive documentation for these AI APIs is available.
• July: The transition to Manifest V3 was fully completed, with Manifest V2 disabled across all channels, including enterprise policy users.
• August: Team members attended events in Berlin, India, and China, including a meetup with the Google Developer Group in Shanghai, highlighting the platform’s growing global community.
• September: Additions to the Side Panel API were shipped as part of Google Summer of Code, including sidePanel.getLayout (to determine panel position) and onopened and onclosed events. Improvements were also made to the error section on the Chrome extensions page.
• November: The new Chrome Web Store API was launched, offering features like service account authentication and partial rollout percentage updates. Detailed API reference documentation and libraries were also released to simplify API interaction. Rollout of new publisher pages displaying all items from a given publisher began. Support for the browser namespace was announced as an alternative to window.chrome global access, addressing compatibility issues with Mozilla’s web extension polyfill library.

III. Technical Details & APIs

• Manifest V3: The latest version of the manifest file format for Chrome extensions, designed for improved security and performance.
• User Scripts API: Allows developers to inject custom JavaScript code into web pages. The userScripts.execute API provides a mechanism for executing this code immediately.
• Chrome Web Store API: Enables programmatic interaction with the Chrome Web Store, allowing developers to automate tasks like submission, updates, and reporting. The API supports authentication with service accounts.
• Browser Namespace: A proposed alternative to the window.chrome global object for accessing extension APIs, aiming to improve compatibility and reduce conflicts.
• Side Panel API: Allows extensions to create persistent side panels within the browser window, providing a dedicated space for extension functionality.

IV. Key Arguments & Perspectives

The speaker emphasizes the importance of community feedback in shaping the platform’s development, citing the changes to the User Scripts API access as a direct result of developer input. The speaker also highlights the platform’s openness to experimentation, particularly with AI, and anticipates further innovation as related technologies mature. The successful transition to Manifest V3 is presented as a collaborative effort, acknowledging the work required from the entire developer community.

V. Notable Quotes

• “2025 is almost over. A lot has happened. The transition to manifest v3 is complete and we've launched new platform APIs in Chrome and a lot of really exciting capabilities in the Chrome web store.”
• “This has honestly been a long time coming, so I'm glad we can finally say it's here.” (Referring to the ability to cancel Chrome Web Store submissions)
• “Thank you for working with us.” (Acknowledging the community’s effort during the Manifest V3 transition)

VI. Synthesis & Conclusion

2025 was a year of significant progress for the Chrome extensions platform and Web Store. The completion of the Manifest V3 transition, coupled with the launch of new APIs and features, has laid a strong foundation for future innovation. The growing adoption of AI and the active community contributions, exemplified by libraries like WXT, demonstrate the platform’s vibrancy and potential. The speaker’s closing remarks express gratitude to the community and anticipation for continued growth in the coming year. The focus on developer experience, through features like the DevTools integration and improved API documentation, underscores Google’s commitment to supporting the Chrome extension ecosystem.