SigmaOS
YC S21San Francisco, US · Founded 2021 · 5 employees · Hiring · 4 known investors
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SigmaOS is a macOS web browser that organizes tabs into workspaces and includes AI-powered features like website summarization and contextual search. It targets students, founders, and creatives seeking improved productivity and focus.
Also known as SigmaOS (S21)
Founders & leadership· Y Combinator alumni (S21)
SigmaOS was founded in 2021 by Mahyad Ghassemi, Ali Attar, Saurav Mitra, and Mahyad Ghassemibouyaghchi.
Investors · 4
Funding
SEC filings, press & company announcements$4M disclosed across 1 of 2 rounds · 2022
- $4MraisedNov 2022 · 2 sourcesSource ↗
Source: company announcements and press reports — follow each round's link for the claim.
Company profile
researched Aug 2026SigmaOS is a macOS web browser built around workspace-based tab organization and keyboard-driven navigation. Tabs (called Pages) are grouped into Workspaces, displayed as vertical lists in a left sidebar, and treated like items in a to-do list that can be marked "done" or locked to keep them open. Additional workflow features include split screen for viewing two sites at once, Focus Mode to hide interface chrome, single-key shortcuts (for example W for a new Workspace, D for done, F for focus), Command-Hover link previews, Magic Theme color matching, a built-in ad blocker, cross-device autosync of a user's setup, and Magic Rename self-naming tabs.
The browser layers AI features under the assistant name Airis. "Ask Anything" lets users chat with the page they are on, find content in their own words, and get in-context explanations; "Look it up" performs multi-page internet research and supports follow-up questions; and "Simplify" condenses a website into a short interactive summary that can be queried further. Lazy Search, opened with the space bar, is a unified search over open Pages, tags, Workspaces, history, bookmarks, internal commands and the web, with command+K filtering to SigmaOS commands only.
SigmaOS supports Chrome Web Store extensions and its own Extensions Manager, several password managers (Apple Keychain, 1Password, Dashlane, LastPass, Keeper, Zoho Vault, Bitwarden), configurable default search engines including DuckDuckGo, Ecosia, You.com and Bing, per-website settings, private browsing Workspaces and separate-cookie Workspaces for multiple logins. Migration tooling imports cookies, active tabs, history, extensions, bookmarks and passwords from Chrome, Safari, Brave, Opera, Firefox, Vivaldi, Edge and Sidekick.
Founding story
Mahyad Ghassemibouyaghchi left Iran in 2016 to study computer science at King's College London. After being diagnosed with ADHD, he set out to build a browser designed to help users stay focused, founding SigmaOS with cofounders Ali Attar and Saurav Mitra.
Business model
SigmaOS operates a freemium consumer software model. A free tier (SigmaOS Personal) is available to anyone, while SigmaOS Personal Pro is sold as a subscription that adds unlimited Workspaces and unlimited devices for auto-sync. The company states it deliberately avoids advertising and search-engine data deals, positioning paid subscriptions as the mechanism that aligns its incentives with users' interests. A referral program grants $5 in credit for each person who signs up through a user's referral link.
Subscription revenue from SigmaOS Personal Pro at $10 per month, or $8 per month billed annually, with a free tier, a 14-day trial and a 50% discount for students and academics. The company states it does not run ads or make search-engine data deals.
Traction
Y Combinator founder profiles state SigmaOS was used by more than 100,000 people and served about 75,000 LLM requests per day. A March 2023 Forbes profile cited more than 100,000 app downloads and 10 million tabs created since the 2021 launch, along with $4 million raised. Y Combinator lists a team size of 5.
Latest developments
TechCrunch coverage from March 2024 described the browser turning to AI-powered features for monetization. The current website markets Airis-powered capabilities — Ask Anything, Look it up, Simplify — along with Lazy Search and Command-Hover as newer additions. Founder profiles on Y Combinator describe SigmaOS in the past tense, with the founders now building Okibi (S25) and Lightberry (F25).
▸Full profile — market position, technology, go-to-market, geography, history
Market position
SigmaOS is a Y Combinator-backed (Summer 2021) alternative browser competing in the productivity-oriented, macOS-first browser category alongside Arc, whose documentation SigmaOS references for switchers. Reported traction includes 100,000+ users, 75,000 LLM requests per day, and 10 million tabs created since launch as of March 2023.
SigmaOS departs from conventional browser interfaces by replacing horizontal tab strips with vertical, workspace-grouped Pages that behave like tasks, and by making browser control modal through single-key shortcuts rather than modifier-key combinations. It combines this with in-browser AI (chat with a page, multi-page lookup, page simplification) and a subscription business model with no advertising, which the company frames as a privacy advantage. Founder profiles describe it as the first web browser designed for work with AI agents built in.
Technology
A macOS desktop browser supporting Chrome Web Store extensions, WebKit Intelligent Tracking Prevention for cookie tracking protection, and Apple Keychain for password storage. AI functionality is delivered through an assistant called Airis that reads page context for chat, search and summarization; founders cite roughly 75,000 LLM requests per day.
Go-to-market
Distribution is direct-to-user: a free macOS download from the company's website, an onboarding tutorial and documentation site, browser migration tooling to move users over from Chrome, Safari, Brave, Opera, Firefox, Vivaldi, Edge and Sidekick, a Slack community for feedback, a referral program offering $5 credit per signup, and a 14-day Pro trial plus a 50% student and academic discount.
Founders, researchers, students, academics and content creators who spend long hours working on the web across many tabs and web apps.
Geography
Y Combinator lists SigmaOS in San Francisco; a posted software engineering role was based in London, UK. The product is distributed as a downloadable macOS application, with a Slack-based user community.
History
The company was founded in 2021 and took part in Y Combinator's Summer 2021 batch, with Gustaf Alstromer as primary partner. Press coverage tracked by Y Combinator records a $4 million raise reported in November 2022, the launch of a contextual AI assistant in June 2023, and a shift toward AI-powered features for monetization reported in March 2024. By March 2023 the company reported more than 100,000 app downloads and 10 million tabs created since launch. Founder profiles later describe SigmaOS as a prior project, with the founders subsequently working on Okibi (S25) and Lightberry (F25).
Compiled by commissioned research from 8 cited public sources — announcements, filings, and press listed under research sources below.
Key figures
latest reportedCompany-reported or press-reported figures, each dated to when it was claimed — not independently audited.
Founder mafia
3 people who came through SigmaOS went on to found or lead other companies.
Competitors · 1
by search overlap
Companies competing with SigmaOS for the same Google search keywords, organic and paid, via search-intersection analysis.
Timeline · 4
launches, deals, and filingsTechCrunch reported that the YC-backed browser was leaning on AI-powered features for monetization.
TechCrunch coverage of SigmaOS launching a contextual AI assistant inside the browser.
TechCrunch reported that SigmaOS raised $4 million to build a productivity-focused browser.
$4M source ↗
SigmaOS was part of Y Combinator's Summer 2021 batch, with Gustaf Alstromer as primary partner.
Dated company events from announcements, filings, and press; legal rows summarize public dockets and regulator releases.
In the news
▸Research sources · 8
primary sources listed
- SigmaOSsigmaos.com · web
8 public sources were cited for this profile; the first-party ones are listed here.
Frequently asked questions
- What does SigmaOS do?
- Y Combinator-backed macOS browser that organizes tabs into workspaces and adds an in-browser AI assistant, Airis.
- Who founded SigmaOS?
- SigmaOS was founded by Mahyad Ghassemi, Ali Attar, Saurav Mitra, Mahyad Ghassemibouyaghchi in 2021.
- Who are SigmaOS's investors?
- SigmaOS's investors include Moonfire Ventures, Y Combinator, 7percent Ventures, LocalGlobe.
- How much funding has SigmaOS raised?
- SigmaOS has disclosed $4M raised across 1 of its 2 known rounds.
- Where is SigmaOS headquartered?
- SigmaOS is headquartered in San Francisco, US.