Open-Sourcing InboxSDK (YC S11) – Build Apps in Gmail

In plain words

InboxSDK is an open-source software development kit that enables developers to build browser extension applications for Gmail. It provides a high-level API for inserting user interface elements into Gmail without direct DOM manipulation, allowing apps to integrate seamlessly into the Gmail workflow. The SDK supports adding UI across multiple Gmail areas and is designed for developers creating tools that target Gmail's 1.8 billion users.

written from the facts on this page · September 2026

From the sources

In the maker’s words, at launch

Hi HN! We’re Aleem, Chris, Borys, Meichen and Zach from Streak (YC S11) and today we’re open sourcing our InboxSDK https://www.inboxsdk.com, which makes it easy to build apps for Gmail. Over 1.8B users spend their days in Gmail! Having your app built into the Gmail workflow is a better user experience and…

• 
  InboxSDK2015 · inboxsdk.com · ▲508

  First usable API to write Gmail Apps for 1B active users

• 
  InboxSDK by Streak (YC S11) – Build Apps inside Gmail2015 · inboxsdk.com · ▲176

  The InboxSDK is high level Javascript library used to easily build browser extensions that interact with Gmail

• EE
  Easy Email Encryption inside Gmail (Alpha, Open-Source)2013 · streak.com · ▲170

  Manage sales and customer relationships directly inside Gmail. Streak is the CRM your team will actually use—integrated, smart, and loved by 750,000+ users.

• 
  Inbox Zero Tabs2025 · chromewebstore.google.com · ▲398

  Split inbox tabs for Gmail. 100% private. 100% free

• 
  Inbox by Google2014 · google.com · ▲1,147

  Next generation inbox

• IM
  I'm working on an open-source Gmail replacement2013 · khamidou.github.io · ▲387

• 
  Run full iOS 16.5 firmware on Android Devices▲513

  Contribute to oosexgang/hackios-xnu-kernel development by creating an account on GitHub.

  Dev tools · 1d ago · github.com

• 
  /dev/null▲492

  a social network for devs

  Dev tools · 4d ago · dev-null.sh

• 
  Whiteboard (YC W26) – an open-source IDE for thoughtful software design▲423

  open-source IDE for thoughtful software design. Contribute to devdotfast/whiteboard development by creating an account on GitHub.

  Dev tools · 29d ago · github.com

• 
  Reladraw – A diagram language where you decide where to place things▲411

  Contribute to reladraw/reladraw development by creating an account on GitHub.

  Dev tools · 27d ago · github.com

• 
  OpenBot▲362

  Grok Bot alternative: free, local, open-source, multiplayer

  Dev tools · 24d ago · openbot.run

• 
  Talanoa▲346

  Hi HN, I’m a fullstack developer, and honestly, I’ve lost count of how many side projects I’ve worked on over the years. But one idea kept coming back to me: a different kind of email client. It first came to me in 2014: “What if we could handle emails more like conversations?” Every year, I’d revisit this concept in my “Build Notes.” Ten years later, no one had built exactly what I had in mind — so I finally decided to do it myself. That’s how Talanoa was born. I wanted something focused on people, not timelines. I was tired of marking messages as unread just to remember to reply later, or…

  Dev tools · 22d ago · talanoa.email

• I3
  I 3D scanned the interior of the Great Pyramid at Giza▲1,752

  Hey HN, I 3d scanned the interior of the Great Pyramid / Khufu's pyramid for the Giza Project this summer and just finished the guided version to share. Would love feedback and/or problems you encounter. I used both a Leica BLK 360 and Matterport Pro 2 to do the scanning and the Matterport SDK for the web viewer. Matterport's web display with Three.js has been the most accessible to a wide audience in the past (previous iterations are in Unity and Unreal, but difficult to download over slower connections). I've been interviewing social studies teachers around the 6th grade level to…

  Dev tools · 2022 · giza.mused.org

• 
  Clay▲819

  Discover, organize, and deepen relationships

  Work · 2022 · me.sh

• 
  Restfox – Open source lightweight alternative to Postman▲758

  Last time I posted this it didn't garner much interest. There have been lots of improvements and fixes since the last release. Quick list of features: - Workspaces - Tabs - Nested Folders - Lots of context menus - Response history - Plugins - Runs fully in the browser and runs offline if necessary - Chrome and Firefox extension to bypass CORS restrictions - Desktop builds for all platforms - GraphQL support - Import collections exported from Postman and Insomnia - Simple user friendly interface I built this because I love Insomnia but wanted a portable version that I could run in the…

  Dev tools · 2022 · restfox.dev

• 
  Sponsor This Newsletter▲707

  100+ newsletters ready to promote your product

  Growth · 2022

• 
  Micro SaaS HQ▲672

  Profitable Micro SaaS ideas, supportive community

  Life & fun · 2022 · microsaashq.com

• 
  America – Road Trip Simulator▲663

  APIs are a little like the open road—always waiting, full of opportunity, but hardly utilized. So here’s America, composed of several APIs that paint a vivid, real-time picture of a good old-fashioned road trip. Get local classifieds and photos. Tune into local radio stations. Talk wit other drivers. And more. Exploring the country by car was an invaluable experience for me during my time in the states. I’ve since moved to Barcelona, and find myself missing the territory. This is my attempt at recreating the magic.

  Life & fun · 2022 · 4m3ric4.com