Apollo.io
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Apollo.io is a sales-intelligence and go-to-market (GTM) platform built around a large business-to-business (B2B) database of contacts and companies, combined with prospecting, data enrichment, email sequencing, dialing, and a growing set of artificial intelligence features. Founded in 2015 in San Francisco as ZenProspect by Tim Zheng, Roy Chung, and Ray Li, the company graduated from Y Combinator's Winter 2016 batch and rebranded to Apollo.io in 2018. After a near-collapse in 2018-2020, including a data breach and a steep revenue decline, Apollo recovered through a product-led growth (PLG) strategy built on a freemium, self-serve product, and grew to roughly $200 million in annual recurring revenue (ARR) by early 2026. Its database covers more than 250 million contacts across tens of millions of companies, and the platform is used by millions of sales, marketing, and revenue professionals at hundreds of thousands of companies.
Apollo.io was founded in 2015 as ZenProspect by CEO Tim Zheng, COO Roy Chung, and CTO Ray Li, and headquartered in San Francisco. Zheng had previously founded an education-technology company (variously reported as Brainscape, BrainGenie, or BrainScape) focused on skills practice; while running it he built internal software to automate targeted outreach, and the tooling worked well enough that other founders asked for access. Ray Li had been a software engineer at Square, and Roy Chung had worked at Doblet, another Y Combinator company. The product set out to combine a lead database with outbound automation so sales reps would not have to toggle between separate prospecting and email tools.
ZenProspect was accepted into Y Combinator's Winter 2016 batch (receiving roughly $120,000 in seed funding) and grew quickly, reaching about $1 million in ARR during the program. Early product reporting described it as a rules engine for automating prospect routing, plus lead scoring and analytics, drawing on a database of around 200 million contacts across roughly 10 million companies along with each customer's own CRM data.
In June 2018 the company rebranded from ZenProspect to Apollo.io, evoking the ambition and precision of the Apollo space program, and launched the Chrome extension that became a signature part of the product.
In mid-2018 Apollo left a copy of its prospecting database exposed online without a password. The exposure was discovered by security researcher Vinny Troia, and on October 1, 2018 the company disclosed the breach. Reports put the exposure at roughly 125 to 126 million unique email addresses and around 9 billion individual data points, including names, employers, job titles, and locations. Apollo emphasized that the exposed records did not include passwords, Social Security numbers, or financial data. A subset of about 126 million email addresses was added to the Have I Been Pwned breach-notification service.
The breach landed during an already difficult stretch and contributed to a sharp business decline. According to later accounts from former employees, revenue fell from roughly $6 million to $7 million down to about $2.5 million, and headcount dropped from around 50 in mid-2018 to roughly 12 by early 2019. Apollo lost a number of marquee accounts during this period.
By 2020 the company faced an existential cash crunch. Zheng has described unit economics so poor that Apollo was spending about $1 to acquire only $0.80 in revenue, with roughly six months of runway left, sliding morale, and departing talent. The high-touch, sales-led motion that targeted large annual contracts was not working at the company's scale.
Apollo's response was to pivot to a product-led growth model: a freemium, self-serve product priced for small and mid-sized businesses, with a low entry point (around $99 per month) in place of the $10,000-plus annual contracts it had been chasing. The shift let prospective users sign up, try the database and sequencing tools, and convert without a sales call. The company has said that more than 90% of new users came through organic channels. Over the following roughly 24 months Apollo tripled in size and crossed $100 million in ARR, and the turnaround became a widely cited PLG case study. The strategy also fed a rapid succession of venture rounds.
On February 3, 2026, Apollo announced that Matt Curl had been appointed Chief Executive Officer, effective immediately, with co-founder Tim Zheng moving to Chairman of the board. Curl had advised the company beginning in 2019 and later joined full-time as Chief Operating Officer; the two had worked together closely for nearly six years. At the time of the transition Apollo said it was approaching $200 million in ARR with nearly 100,000 paying customers, and had posted its strongest January, fourth-quarter, and year-to-date revenue growth to date. Zheng remained actively involved as Chairman.
Apollo raised a series of venture rounds as its PLG model accelerated, reaching unicorn status (a private valuation above $1 billion) with its 2023 Series D. Across all rounds the company has raised on the order of $250 million.
| Round | Date | Amount | Lead investor(s) | Valuation | Notes |
|---|---|---|---|---|---|
| Seed (Y Combinator) | Winter 2016 | ~$120K | Y Combinator | n/a | As ZenProspect |
| Series A | June 2018 | $7M | Nexus Venture Partners | n/a | Social Capital and Y Combinator also participated; coincided with the Apollo rebrand |
| Series B | Nov 1, 2021 | $32M | Tribe Capital | n/a | NewView Capital and existing investor Nexus Venture Partners participated; total funding ~$40M after |
| Series C | March 3, 2022 | $110M | Sequoia Capital | ~$900M (reported) | Tribe Capital, Nexus Venture Partners, and NewView Capital also participated |
| Series D | Aug 29, 2023 | $100M | Bain Capital Ventures | $1.6B | Sequoia Capital, Tribe Capital, and Nexus Venture Partners participated; brought total raised to ~$250M |
At the Series B in November 2021, Apollo reported more than one million user signups, about 9,000 paying customers, more than 200% user growth over the prior year, and 18-plus months of profitability. By the Series C in March 2022, over a million users across 160,000 companies had signed up in the prior year, and paying customers had grown to more than 15,000 (up about 60% from 9,000 the previous quarter). The Series D in August 2023 was described by TechCrunch as the largest non-private-equity round for a US sales-tech startup that year; Apollo cited roughly 9x revenue growth over the prior two years, more than three million GTM professionals using the product, and over 500,000 companies served, with named customers including Qualtrics, Customer.io, and Census. Bain Capital Ventures partner Merritt Hummer joined the board.
It should be noted that some secondary write-ups place the Series C in 2021 or attribute the $1.6 billion valuation to that round; primary sources, including Apollo's own announcement and contemporaneous TechCrunch and Crunchbase reporting, date the $110 million Series C to March 2022 at a roughly $900 million valuation, and tie the $1.6 billion valuation to the August 2023 Series D.
Apollo positions itself as an all-in-one GTM platform, layering engagement and automation tools on top of its proprietary B2B database.
The core asset is a large B2B "data graph." Reported sizes have grown over time, from roughly 200 million contacts at the YC stage to about 220 million by 2021, 270 million verified contacts cited at the 2023 Series D, and figures in the range of 250 million to 265 million contacts across tens of millions of companies (commonly cited as over 60 million companies) by 2025-2026. Apollo says it tracks more than 200 data attributes per record and sources data from public web pages (including profiles), third-party providers, and contributions from its own large user base.
Data enrichment keeps customer records current. Apollo connects to CRMs such as Salesforce and HubSpot, periodically scanning records to fill in missing phone numbers, update job titles, and flag duplicates. The company has promoted "waterfall enrichment," in which Apollo checks its own data first and then queries selected trusted third-party sources to fill gaps, reporting incremental gains in email and phone coverage and fewer bounces. Job-change and promotion alerts notify reps when a contact moves roles.
A browser extension (initially for Chrome) lets users prospect directly from sites such as LinkedIn, pulling contact details and saving people into Apollo sequences. Sequences are multi-step, multi-channel outreach campaigns spanning email, calls, and tasks. Apollo includes a built-in dialer, and added a parallel dialer that can call multiple numbers at once to raise connect rates, along with location-based call-recording rules for compliance and AI-generated call summaries to ease the handoff from sales development representatives (SDRs) to account executives.
AI has become central to Apollo's product and marketing. Capabilities include:
These features build on large language models and generative AI to combine natural language processing with Apollo's structured data, and the company stresses a human-in-the-loop design in which users can throttle or gate AI actions. As of 2025 Apollo said its AI capabilities had grown about 500% year over year, with more than 50,000 weekly active users of its AI tools and tens of millions of AI-driven prospecting actions in a single year. Apollo's data has also been embedded into third-party AI products, including HubSpot's Breeze prospecting agent.
Apollo has expanded beyond outbound prospecting into inbound and revenue operations. An inbound add-on bundles website visitor identification and form enrichment to capture, enrich, route, and convert inbound leads, while RevOps-oriented enrichment cleans CRM data at scale. Meeting scheduling, conversation intelligence, and analytics round out the platform.
Apollo uses a freemium model with four main tiers, billed per user with a credit system for actions such as exporting records and revealing mobile phone numbers. Annual billing carries roughly a 20% discount versus monthly. Reported list prices for 2025 were approximately:
| Plan | Price (annual, per user/month) | Notes |
|---|---|---|
| Free | $0 | Limited monthly credits, two active sequences, access to the contact database |
| Basic | ~$49 ($59 monthly) | More credits and sequences |
| Professional | ~$79 ($99 monthly) | Higher credit allotments and additional features |
| Organization | ~$119 ($149 monthly) | Minimum 3 users; highest allotments and admin controls |
Email credits are generally unlimited under a fair-use policy, while mobile-number and export credits are metered; pricing details have changed over time, so the figures above should be treated as indicative.
Apollo's revenue grew rapidly after the PLG pivot. Independent trackers and Apollo's own announcements describe ARR rising from roughly $96 million in 2023 to about $134 million at the end of 2024, around $150 million by May 2025, and approaching $200 million by early 2026. User and customer counts grew in parallel, from about 9,000 paying customers in 2021 to more than 15,000 in 2022, and to nearly 100,000 paying customers by early 2026, with the user base reported in the millions (about three million GTM professionals at the 2023 Series D, and figures around four million users thereafter) across more than 500,000 to 600,000 companies. Headcount expanded from roughly 12 at the 2019 low point to several hundred by 2023 and beyond 1,000 by the mid-2020s, distributed across more than 20 countries.
Apollo competes with sales-intelligence and engagement vendors including ZoomInfo, Cognism, Lusha, Clay, Outreach, Salesloft, and Seamless.AI. It is frequently positioned as a lower-cost, self-serve alternative to ZoomInfo, pairing a large database with built-in engagement tooling. Reviews commonly praise the breadth of data and value for the price, while noting variability in data accuracy (a recurring critique of the category) and that heavy reliance on credits can raise effective costs for high-volume teams.
The most significant incident in Apollo's history is the 2018 data breach described above, in which a large copy of its contact database was left publicly accessible and ultimately added to breach-tracking services. As with other contact-data aggregators, Apollo has also faced ongoing scrutiny over how it collects and sells personal and professional information and over data-accuracy and compliance concerns, which the company addresses through enrichment controls, opt-out mechanisms, and region-specific recording and privacy features.