Side-by-side IPO readiness, funding history, and valuation comparison. Data sourced by TechStackIPO.
Scores, valuations, and signals for OpenAI, Substack, and 370+ companies. 5-min read every Tuesday.
OpenAI is valued at $852B — the world's most valuable AI company, backed by $27B in funding. Track IPO readiness score, funding rounds, and timeline.
| Industry | Artificial Intelligence |
| Stage | Pre-IPO |
| IPO Status | Pre-IPO |
| Valuation | $852B |
| Total Funding | $55.4B |
| Headquarters | San Francisco, CA |
Newsletter publishing platform enabling writers to build paid subscription audiences.
| Industry | Media Technology |
| Stage | Series B |
| IPO Status | Pre-IPO |
| Valuation | $650M |
| Total Funding | $90M |
| Headquarters | San Francisco, CA |
OpenAI is valued at $852B. Substack is valued at $650M. Both valuations are based on the most recent private funding rounds tracked by TechStackIPO.
OpenAI has raised $55.4B. Substack has raised $90M.
OpenAI is currently pre-IPO. Substack is currently pre-IPO. Track both on TechStackIPO for S-1 filings and IPO announcements.
OpenAI operates in Artificial Intelligence, while Substack operates in Media Technology.
OpenAI is a Artificial Intelligence company valued at $852B with $55.4B raised. Substack is a Media Technology company valued at $650M with $90M raised. See TechStackIPO's full side-by-side comparison for IPO readiness scores, funding timelines, and investor data.
Accredited investors can access pre-IPO shares in OpenAI and Substack through secondary market platforms, pre-IPO funds, and broker-dealer platforms that facilitate private company transactions. TechStackIPO's marketplace section tracks available access options for both companies. Pre-IPO investments carry higher risk and limited liquidity.