Perplexity AI

Sierra

Perplexity AI

Perplexity uses a freemium model. The free tier gives unlimited basic searches powered by a standard model.

Perplexity Pro costs $20/month and gives access to more powerful frontier models from OpenAI, Anthropic and Google, alongside Perplexity's own, unlimited Pro searches, file uploads, and image generation. Perplexity Enterprise Pro is designed for businesses with team management and API access.

The company also recently introduced advertising through "sponsored follow-up questions" — a controversial move that some see as inevitable and others see as the beginning of the end for ad-free search.

Sierra

Companies pay Sierra to run their customer service with AI agents instead of hiring rooms full of humans. The agent talks to your customers over chat.

It answers questions. It processes returns.

It updates subscriptions. Here is the clever part.

Sierra charges based on outcomes, not seats. Brands pay when the AI actually resolves a problem, not just for having the software installed.

That pricing is unusual. Most software charges a flat monthly fee no matter what.

Sierra only gets paid when the bot does the job.

Perplexity AI

Aravind Srinivas grew up in Chennai, India, got a PhD in AI from UC Berkeley, and worked as a research intern at OpenAI and a researcher at DeepMind. He watched the ChatGPT explosion in late 2022 and saw something everyone else missed: AI chatbots were interesting, but AI-powered search was potentially more valuable.

Google search hadn't fundamentally changed since 1998. It still showed you a list of links and made you do the work of reading and synthesizing information.

Srinivas co-founded Perplexity AI in August 2022 with Denis Yarats (ex-Meta AI), Johnny Ho (ex-Quora), and Andy Konwinski (co-creator of Apache Spark). Their idea was an "answer engine" — you ask a question, Perplexity searches the internet in real time, reads the sources, and gives you a synthesized answer with inline citations.

No ads. No SEO spam.

Just answers.

The product launched quietly and grew through word of mouth among researchers, developers, and knowledge workers who were frustrated with Google's increasingly ad-cluttered, SEO-gamed results. Within a year, Perplexity was handling millions of queries daily.

Sierra

Bret Taylor had already done the impossible twice. He co-created Google Maps.

He later became co-CEO of Salesforce, chaired Twitter's board during the messy Elon Musk takeover, and became chairman of OpenAI in late 2023. Clay Bavor spent 18 years at Google, most recently running its Labs group.

The two friends left their big jobs in 2023 to build something together. They picked customer service on purpose.

It is the least glamorous corner of software. Their logic was simple.

Companies hate their support costs. Customers hate waiting on hold.

AI that actually resolves problems could fix both sides at once. They launched Sierra in February 2024 with $110 million from Sequoia and Benchmark.

Perplexity AI

Perplexity grew almost entirely through product quality and word of mouth. The first users were AI researchers and tech workers who shared it on Twitter.

Every time someone used Perplexity and got a better answer than Google, they posted about it. The product was its own marketing.

The mobile app was a growth accelerator. By launching on iOS and Android early, Perplexity captured users who wanted quick answers on their phones.

The app was faster than opening a browser and Googling — one tap, ask your question, get an answer. Mobile usage now exceeds desktop.

Strategic distribution deals expanded reach. Perplexity partnered with SoftBank (default AI assistant on SoftBank phones in Japan), Deutsche Telekom, and various hardware manufacturers to be pre-installed as the default search assistant.

These deals put Perplexity in front of millions of users who had never heard of it.

Sierra

Sierra went straight for big brands, not tiny startups. SoFi, Ramp, ADT, Sonos and Brex signed up early.

By 2026 it said more than 40% of the Fortune 50 were customers. The trick was trust.

Enterprises are terrified of an AI bot going rogue and insulting a customer. So Sierra built guardrails and let each company control exactly how the agent behaves.

Bret Taylor's contacts did the rest. When the chairman of OpenAI calls a Fortune 500 CEO, they pick up.

Sierra hit $100 million in annual recurring revenue in November 2025, seven quarters after launch, and $150 million by February 2026. In April 2026 it launched Ghostwriter, which builds and deploys a new agent from a plain-English description.

Perplexity AI

Google is the elephant in the room. Google controls 90%+ of the search market and generates $175 billion annually from search advertising.

Google has responded to Perplexity by adding AI Overviews to search results — essentially copying the answer engine concept. Google has unlimited data, unlimited compute, and the default position on every browser and phone.

Competing with Google for search is historically a death sentence.

The publisher problem is real and litigious. Perplexity synthesizes content from news articles and websites without driving traffic back to those publishers.

Multiple media companies have accused Perplexity of scraping their content and delivering it as answers, depriving them of page views and ad revenue. The New York Times, Forbes, and Condé Nast have all raised concerns.

If publishers successfully block Perplexity or win legal challenges, the product's utility decreases.

Monetization without ads is nearly impossible at scale. Perplexity initially positioned itself as the ad-free alternative to Google.

But $20/month subscriptions can't fund the compute costs of an answer engine serving hundreds of millions of queries. The introduction of sponsored questions signals that pure subscription revenue isn't enough.

Whether Perplexity can add ads without becoming what it set out to replace is the defining question.

Sierra

Everyone is building AI customer service agents right now. Decagon has raised at a multi-billion valuation.

Salesforce, ServiceNow and Intercom all shipped their own agents. Sierra is not the cheap option.

It sells premium AI to giant companies that move slowly. The bigger risk sits underneath the product.

Sierra does not make its own AI models. It rents them from providers like OpenAI and Anthropic.

If those model makers decide to compete directly, Sierra's edge gets thin fast, and its co-founder chairing one of them only makes that question louder. A $15.8 billion valuation on roughly $150 million in revenue leaves almost no room for a stumble.

Perplexity AI

Perplexity Search is the core — ask any question and get an AI-synthesized answer with cited sources. Pro Search performs multi-step research, asking clarifying questions and digging deeper for complex queries.

Perplexity Pages lets users create shareable research articles from their queries. Collections organize saved searches and threads.

The Perplexity API lets developers integrate the answer engine into their own products. Perplexity recently added Spaces for team collaboration on research projects.

Sierra

The core product is the Sierra AI agent. It is a branded customer service bot that companies deploy on their website, app, and phone lines.

It handles the boring stuff. Order tracking.

Refunds. Password resets.

Account changes. Sierra also built its own tools to test and monitor these agents so they do not make things up.

In 2024 the company added a voice version that talks to customers on the phone. In April 2026 it added Ghostwriter, a tool that builds and deploys a new agent from a plain-English description.

The whole pitch is one AI agent that carries your brand's name and never sleeps.

Perplexity AI

Jeff Bezos, IVP, NEA, Databricks Ventures, Nvidia, SoftBank

Sierra

Sequoia Capital and Benchmark wrote the first checks at launch in February 2024, $110 million between them. Greenoaks Capital then led both the $175 million round in 2024 and the $350 million round in September 2025.

In May 2026 Tiger Global and Google's GV led a $950 million round at a $15.8 billion valuation, with Benchmark, Sequoia and Greenoaks back in. That takes total funding to about $1.6 billion.

That is partly the product and partly Bret Taylor. Investors bet on founders who have already built billion-dollar things.