Similarweb is a publicly traded company that estimates how many people visit websites and use apps, where those visitors come from and what they do next, for sites and apps it has no direct access to. It exists because the owner of a website sees its own analytics and nothing else. A retailer can read its Google Analytics reports but cannot read a rival's. Similarweb sells modelled estimates of everyone else's numbers: visits, unique visitors, traffic sources, search keywords, referral paths, app usage and, increasingly, behaviour inside AI assistants. Founded in Tel Aviv in 2007 by Or Offer, it has been listed on the New York Stock Exchange under the ticker SMWB since May 2021.

Where the numbers come from

Similarweb does not count visits the way a site's own tag does. It builds estimates from four categories of input, according to its data methodology page.

  • Direct measurement: website and app owners connect their first-party analytics, typically Google Analytics, to Similarweb. The company says "millions of websites and apps" share data this way. These connected sites act as ground truth for training models.
  • Contributory network: consumer products, such as browser extensions and apps, that collect anonymous behavioural data from the devices they are installed on. This is the panel, the core of the system.
  • Partnerships: data bought or exchanged with internet service providers (ISPs), measurement companies, demand-side platforms (DSPs) and corporate intelligence firms.
  • Public data extraction: crawling of public web pages and app store listings, plus reference data such as census population figures.

The modelling layer then combines these streams. Similarweb describes machine-learning calibration, "noise and bias reduction" and a "cross-validation process to ensure scale and trend accuracy on a daily basis". In practice, the panel shows what a sample of users did, directly measured sites show how panel behaviour relates to true totals, and models extrapolate to whole countries and device types.

As of November 2026, Similarweb's Our Data page cites 10 billion digital signals collected each day, coverage of more than 100 million websites and 4 million apps and 10 years of history. None of these figures is independently audited.

What the product reports

The output is organised by domain and app. For a given site, Similarweb reports total visits, unique visitors, pages per visit, visit duration and bounce rate, split by country and by desktop or mobile web. Traffic is broken into channels: direct, organic search, paid search, referrals, social, email and display advertising. Search modules estimate which keywords send traffic and how much is branded.

Around that core sit products for specific buyers. Web Intelligence serves marketers and strategy teams. App Intelligence, expanded after the 42matters acquisition in 2024, covers Android and iOS apps. Ad Intelligence tracks display, search and video ads, built partly on the Admetricks and The Search Monitor acquisitions. Investors buy the same signals as alternative data to forecast company revenue before earnings. Bloomberg integrated Similarweb data into its terminal in June 2025.

A worked example shows the method's reach and its limits. Similarweb's September 2026 primer on Anthropic, built from its web and app panels, estimated that claude.ai received 950 million visits in August 2026 with only 0.46% of them from paid traffic, against 148 million a year earlier. The same report listed what the panel cannot see: application programming interface (API) usage, enterprise contract values and traffic through cloud platforms. In its own words, the panel "corroborates the reported figures and cannot audit them".

Origin and evolution

Or Offer started the business as SimilarGroup, whose first product, Similar Sites, recommended websites resembling the one a user was viewing. It later moved into site rankings and then traffic estimation. Naspers led an $18 million round in February 2014, and small acquisitions such as Quettra in 2015 extended it into mobile apps.

The flotation came in May 2021. Similarweb completed its NYSE initial public offering at a valuation of about $1.6 billion, according to Globes. Acquisitions continued as a public company: Embee Mobile in November 2021, the rank-tracking firm Rank Ranger on May 16, 2022, Admetricks in March 2024, 42matters in July 2024 and The Search Monitor on March 31, 2025.

The business took years to turn profitable. Similarweb reported its first positive free cash flow as a public company with its fourth quarter 2023 results. Revenue for 2025 reached $282.6 million, up 13%. In the second quarter of 2026, revenue rose 9% to $77.2 million and the company recorded its first quarter of positive operating profit under generally accepted accounting principles (GAAP), at $0.7 million, according to its August 12, 2026 results release. Annual recurring revenue (ARR) passed $300 million in June 2026, and full-year 2026 revenue guidance was raised to $314 million to $318 million.

The product mix shifted with AI. Similarweb launched its GenAI Intelligence Toolkit on July 28, 2025, tracking brand mentions inside ChatGPT, Perplexity, Gemini and other assistants alongside the visits those assistants send. A Model Context Protocol (MCP) server followed in September 2025, letting AI agents query Similarweb data directly. A third revenue line emerged: licensing traffic data to large language model (LLM) developers. The company signed a seven-figure LLM data training contract in the first quarter of 2026 with an existing large technology customer.

Why marketers rely on it

Competitive benchmarking is the original use. Without access to a rival's analytics, a Similarweb share-of-traffic chart is often the only comparative view available.

Its role in industry reporting has grown with AI search. Much of what the trade press knows about traffic to AI assistants comes from Similarweb's panel. PPC Land has reported Similarweb data showing ChatGPT's share of generative AI website traffic falling to 52.7% by May 2026 while Gemini climbed to 27.3%, and ChatGPT referrals to news sites growing 25 times year on year. A Similarweb panel study of US desktop users found that brands recommended by ChatGPT were 2.5 times more likely to receive a visit within seven days, with 55.9% of that influenced traffic arriving through search rather than as a referral.

Limitations and criticisms

Accuracy is the persistent question. A peer-reviewed study by Bernard Jansen, Soon-gyo Jung and Joni Salminen, published in PLOS ONE in May 2022, compared Similarweb with Google Analytics across 86 websites in 26 countries. Similarweb's averages were 19.4% lower for total visits and 38.7% lower for unique visitors, while bounce rate came out 25.2% higher and session duration 56.2% higher, according to the paper's abstract. The gaps were systematic, and rankings between the two sources correlated strongly. The authors described Similarweb's visit figures as "conservative". Similarweb's own position is that "there isn't a single source of truth"; its support documentation says it is "more confident" in estimates for sites above 100,000 monthly visits, and that two direct measurement tools can disagree by up to 30% for the same site.

Small sites suffer most. Panels are samples, so estimates for niche business-to-business (B2B) sites, local businesses and new domains rest on few observations, and the company publishes no confidence intervals.

Data collection has drawn scrutiny. A 2021 investigation by Globes reported that until 2017 Similarweb gathered browsing data through extensions in ways that breached user privacy and the terms of Google and Mozilla. It cited 2016 research from Northeastern University linking extensions to the company, and the 2018 removal of the Stylish extension, owned by Similarweb, from Chrome and Firefox after the developer Robert Heaton showed it sent users' browsing history to the company. Similarweb told Globes the earlier reports were groundless and that it now runs strict compliance systems. Its methodology page says it collects no personally identifiable information and no IP addresses.

Opacity cuts across all of it. Panel size, panel composition by country and device, and the weighting of each source are not published. The AI products inherit the issue: when Similarweb reported sponsored ads in 26% of ChatGPT responses, it did not disclose panel size, and Adthena, measuring the UK with scraped prompts, recorded no ads in the same month.

Not the same as

  • Google Analytics and other site analytics: these count a single site's own visitors through a tag on its pages. Similarweb estimates traffic for any site from outside, without a tag.
  • Comscore and Nielsen: audience measurement firms whose ratings are used as advertising currency and are audited by the Media Rating Council (MRC). Similarweb's data is not MRC-accredited and is not traded on.
  • Semrush and Ahrefs: search engine optimisation (SEO) suites that also estimate traffic, but mainly by modelling rankings, search volume and click-through rates. Similarweb's estimates lean on behavioural panels instead.
  • Alexa and Cloudflare Radar: Amazon's Alexa ranking, retired in 2022, was the best-known earlier panel ranking. Cloudflare Radar ranks domains from DNS queries to its resolver, not from a panel.

Recent developments

Leadership is changing. On May 13, 2026, Similarweb began a formal search for a successor to Or Offer, and on September 24, 2026 it named Michael Akkerman, previously chief business officer of Digital Turbine, as chief executive officer, effective November 2, 2026.

The AI pivot continues. Similarweb launched its AI Ads dataset on August 17, 2026, covering paid placements in ChatGPT, Google AI Mode and AI Overviews. Harel Amir, head of product for Ad Intelligence, called it "the rare moment when a major ad channel is still wide open". On September 2, 2026, NIQ and Similarweb announced a product to measure shopping through ChatGPT and Gemini, due in the fourth quarter. Third-quarter 2026 results, the first under Akkerman, are scheduled for November 17, 2026.

Timeline

  • 2007: Or Offer founds SimilarGroup in Tel Aviv; its first product is Similar Sites.
  • February 2014: Naspers leads an $18 million funding round.
  • December 2015: Similarweb acquires Quettra.
  • 2016: Northeastern University researchers link browser extensions to Similarweb's data collection.
  • 2018: Chrome and Firefox remove the Stylish extension, owned by Similarweb, over browsing data collection.
  • May 2021: Similarweb lists on the NYSE as SMWB at a valuation of about $1.6 billion.
  • November 2021: Similarweb acquires Embee Mobile.
  • May 16, 2022: Similarweb acquires Rank Ranger.
  • May 2022: PLOS ONE publishes the 86-website comparison with Google Analytics.
  • Early 2024: Similarweb reports its first positive free cash flow as a public company, for Q4 2023.
  • March 2024: Similarweb acquires Admetricks.
  • July 2024: Similarweb acquires 42matters.
  • March 31, 2025: Similarweb acquires The Search Monitor.
  • June 2025: Bloomberg integrates Similarweb data into its terminal.
  • July 28, 2025: GenAI Intelligence Toolkit launches.
  • September 2025: Similarweb MCP server launches.
  • Q1 2026: Seven-figure LLM data training contract signed.
  • May 13, 2026: CEO succession process announced.
  • June 2026: ARR passes $300 million.
  • August 12, 2026: Q2 2026 results show first positive GAAP operating profit.
  • August 17, 2026: AI Ads dataset launches.
  • September 2, 2026: NIQ and Similarweb announce AI shopping measurement.
  • September 24, 2026: Michael Akkerman named CEO.
  • November 2, 2026: Akkerman takes office.
  • November 17, 2026: Q3 2026 results scheduled.

Summary

Who: Similarweb, founded by Or Offer in 2007 and led since November 2, 2026 by Michael Akkerman, sells the data to marketers, agencies, publishers, investors and AI developers. Comscore, Semrush, Ahrefs, Adthena and Cloudflare offer competing or overlapping measures.

What: A digital intelligence company that estimates traffic, engagement, traffic sources, keywords, ads and app usage for websites and apps it does not own, by modelling panel, partner, public and directly measured data.

When: Founded in 2007, listed on the NYSE in May 2021, reached its first GAAP operating profit in the second quarter of 2026 and is due to report third-quarter 2026 results on November 17, 2026.

Where: Headquartered in New York with major operations in Givatayim, Israel, and London; its estimates cover sites and apps in about 190 countries.

Why: Site owners can see only their own analytics. Similarweb fills the gap with outside estimates used for competitive benchmarking, investment research and, increasingly, measuring AI assistants, while facing persistent questions about accuracy for small sites, panel transparency and its past data collection practices.