How 9 YC Startups Built Their Organic Growth Engine | Iron Index
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Research<br>How 9 YC Startups Built Their Organic Growth Engine<br>Eight years of organic traffic data across nine YC startups. A founder-friendly SEO case study on what each organic growth engine looks like, where each company bet, and what's working in 2026.<br>Ramiz I.<br>· April 26, 2026 · 22 min read
// table of contents ▾<br>For four years, Rippling’s organic traffic looked dead. Through January 2022, the company was pulling under 10,000 monthly visits while Brex, same YC batch, was already at 115,000. If you’d put those two graphs side by side in early 2022, you’d have called Brex the SEO success story and quietly killed Rippling’s program.
By March 2026, Rippling was at 552,000 monthly visits, nearly 4x Brex. The flat line became the steepest growth curve in this study, and the most interesting one to dissect.
Figure 0.1<br>Rippling vs Brex: Same W17 Batch<br>Monthly organic traffic, half-year averages, 2018 to 2026.<br>0 100K 200K 300K 400K 500K 600K 201820192020202120222023202420252026 Feb 2022 inflection Rippling Brex<br>Source: Semrush historical organic traffic, US database. Half-year averages.<br>IRON INDEX
That contrast is the reason I pulled this dataset together. I wanted to know what each of these nine companies actually built, what’s compounding right now in 2026, and what the data tells you about running an SEO program at an early-stage company where the graph won’t look like progress for two or three years.
These nine companies span Y Combinator batches S15 to S20. Every one is a unicorn or close to it. Some won on programmatic. Some won on editorial. One won on patience. Here’s what I found.
// methodology<br>Data: Semrush US, pulled March 2026. Historical curves back to 2018.<br>Scope: Top-level domain plus subdomains. US only.<br>Classification: Top 50 pages per company, hand-classified by what they actually rank for.<br>Caveats: Numbers are directional estimates, not GA-grade actuals.
The standings
Here’s where each company sits in March 2026, ranked by current monthly organic traffic. The leaderboard is just the snapshot. The shape of each curve underneath it is the more interesting story, which is what most of this piece is about.
Figure 1.1<br>Monthly Organic Traffic, March 2026<br>Where each company stands today.<br>Gusto
1,182,834
Rippling
551,955
Faire
375,914
Webflow
317,083
Deel
172,856
Brex
154,818
Mercury
143,164
Glean
90,022
Vanta
58,396
Source: Semrush, US database, March 2026.<br>IRON INDEX
Gusto leads at over 1.1 million monthly visits , more than double the next company on the list. The W17 batch (Rippling, Faire, Brex) tells a more interesting story. Rippling is second highest in the entire study at 552K. Faire is third at 376K. Brex, the company most people associate with SEO at YC, is sixth at 155K. Same batch, very different YC startup SEO outcomes.
Then you have the younger companies. Deel just crossed 170K despite only launching real organic activity in mid-2022. Glean and Vanta are the smallest, but as we’ll see, they’re moving faster than anyone else right now.
Raw traffic is just the snapshot. The more interesting question is what each one did to get here.
Here’s what the data made clear after running it across all nine. There is no single playbook for organic at this scale. These companies didn’t pick the same architecture, didn’t ship at the same cadence, and didn’t even bet on SEO with equal conviction. What they share is more about commitment than timing. The ones with durable engines made an architectural bet that fit their business and put real weight behind it for years. The ones still flat are still hedging.
Strategy by strategy
The phrase “startup SEO strategy” gets thrown around a lot. What I mean by it specifically is: where the traffic actually comes from. Not what the team says they do. What the data shows they built.
I pulled the top 50 highest-traffic pages on each domain and classified them by type: programmatic, editorial, product, glossary, comparison, landing, or other. The mix tells you exactly what each company bet on. What follows are nine SaaS SEO examples, same starting point, very different outcomes.
Gusto<br>S15 · 1.18M traffic · +11% YoY
Programmatic at scale, paired with brand. 23 of the top 50 pages are programmatic: salary tools, payroll calculators by city and state, paycheck calculators by hourly and salary structure. These pages were built once and have been compounding for almost a decade. The homepage carries 73% of top 50 traffic on its own, which tells you the brand is doing real work, but the programmatic surface is what gives Gusto its scale.<br>Programmatic Salary ToolsState PagesBrand
Rippling<br>W17 · 552K traffic · +27% YoY
Editorial-led, with a glossary backbone. 30 of the top 50 are blog posts on payroll, HR, security, and operations topics. Six glossary pages add quiet support. Almost no programmatic. The interesting twist is what came after Rippling started...