Google Summer of Code 2025 for Chromium

🚀 Chrome Extension APIs

Hello, this is Amit! I created this repository as a dedicated hub for my final work product submission, which illustrates and highlights my contributions to Chromium during Google Summer of Code - 2025.

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💡Project Links

• GSoC Project Page
• Project Proposal
• WECG Github
• Changes Made

🛠️ Project Overview

The goal: Improve the Chrome Extensions developer experience by enhancing debugging tools, APIs, and extension workflows.

Main focus areas:

• Improvements to chrome://extensions page (the hub where developers manage/debug their extensions).
• New/Improved Extension APIs (aligning with WECG standards).
• Better debugging experience for Manifest V3 extensions.

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🔨 My Contributions

1. Extensions Page – Better Error Visibility

Imagine seeing "Errors" on the extensions page every time, even if there were only some harmless warnings. Frustrating, right?
This was the very first bug I worked on in Chromium — and it taught me a lot about how UI labels are tied to backend logic.

• Before: Always showed “Errors” → confusing when only warnings existed.
• After: Now shows “Warnings” when appropriate.
• Result → Developers instantly know whether it’s a critical issue or just a small warning.

📸 UI Update:

Before	After

🔗 Code Change

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2. Debugging Made Easier – View in DevTools Button

I remember spending time trying to open the right DevTools for debugging extension errors. It wasn’t straightforward.
So I added a shortcut: a shiny new "View in DevTools" button. One click → you’re in the exact DevTools context you need.

• Added a button in the extension error page to open the right DevTools target directly.
• No more manually finding the right SW or background page!

📸 UI Update:

Before	After

🔗 Code Change

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3. RuntimeError Enhancements

Debugging service workers in extensions is already tricky. I worked on adding metadata (isServiceWorker, canInspect) so Chromium knows where exactly the error belongs.
This way, even if a Service Worker is inactive, DevTools can spin it up and take you to the right place.

• Added:
  • isServiceWorker → flags if error belongs to a Service Worker.
  • canInspect → allows DevTools inspection if error is from a SW.
• Enables correct DevTools target selection (even for inactive SWs).

🔗 Code Change

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4. New API: getSystemUILanguage() (WIP)

Ever wondered how an extension knows your system’s UI language? I implemented an API that gives this info as a proper BCP 47 language tag — cross-platform and standards-compliant.

• Returns OS language as BCP 47 tag (en-US, fr-FR, etc.).
• Special handling for C/POSIX → maps to en-US.
• Cross-platform support: Windows, macOS, Linux.
• Added comprehensive test coverage.

🔗 Code Change

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5. Alarms API – Persistence Across Sessions (WIP)

• Added persistAcrossSessions flag in chrome.alarms.create.
• Default: true → alarms survive browser restarts.
• Session-only alarms vanish after restart.

📸 Example Flow:

chrome.alarms.create("dailyCheck", { delayInMinutes: 5, persistAcrossSessions: true });

🔗 Code Change

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6. DNR – Request Header Matching (Partial)

Think of content-blocking extensions. They often need to filter requests based on headers like User-Agent.
I laid the groundwork for this by adding IDL types and parsing logic — ensuring headers are valid, consistent, and safe to use.

• Added IDL types and parsing for request headers.
• Validates header names, values, and excluded values.
• Ensures rules remain consistent (e.g., no conflicts between include/exclude headers).

🔗 Code Change

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7. DNR – Regex Substitution Transforms (Work in Progress)

Imagine capturing a query string like q=hello%20world. Without decoding, it looks messy.
With my WIP feature, you can transform regex groups (e.g., decodeURIComponent) before substitution → "hello world" instead of "hello%20world".

• Extends Declarative Net Request substitutions with transform operations.
• First operation: decodeURIComponent.
• Designed to be extensible for future transforms (e.g., toLowerCase, encodeURIComponent).

📜 Example manifest:

"regexSubstitutionTransforms": [
  { "group": 1, "operation": "decodeURIComponent" }
]

🔗 Code Change

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🏄‍♂️ Challenges

Working on Chromium was both exciting and challenging. Some of the toughest hurdles I faced:

• 🧩 Huge Codebase → Navigating millions of lines of C++ and JS while understanding the extensions architecture.
• 🔄 DevTools Integration → Figuring out how DevTools connects with background contexts and service workers.
• 🧪 Testing Complexity → Understanding Chromium’s testing framework was tough. I had to learn how to design and add the right test files that covered edge cases thoroughly, while making sure I didn’t break or alter existing logic and flows.
• 📏 Standards vs. Implementation → Balancing WECG specifications with Chrome-specific requirements.
• ⏱️ Debugging Build Issues → Chromium builds are long and resource-heavy; fixing small errors often meant multiple rebuilds.

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🔮 Future Goals

My journey with Chromium doesn’t stop here. I’m looking forward to:

• ✅ Completing DNR header indexing for full request header matching.
• ⚙️ Finishing regex substitution transforms to allow flexible query parameter handling.
• 🌱 Exploring more opportunities to contribute to the Chromium Extensions team — whether through GSoC 2026 or independent contributions outside the program.

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☀️ Mentors

I am deeply grateful to my mentors:

• Oliver Dunk
• Solomon Kinard
• Sreeja Kamishetty

for their guidance, patience, and detailed reviews. Every discussion helped me sharpen my approach and think like a browser engineer.

Oliver Dunk ✉️ Email 🔗 GitHub	Solomon Kinard ✉️ Email 🔗 GitHub	Sreeja Kamishetty ✉️ Email 🔗 GitHub

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📌 A Quick Recap of My GSoC Journey

• 🚀 Contributed to the Chromium codebase for GSoC’25 under the Chrome Extensions team.
• 🛠️ Gained hands-on experience with browser internals, debugging flows, and API design.
• 🧪 Learned to write robust tests that catch edge cases without disrupting existing flows.
• 🎯 Managed complexity in a massive open-source project.
• 💡 Built confidence in collaborating with mentors and the community.
• 🌱 Most importantly → I grew from being just a user of Chrome to a contributor to the browser itself.

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