Brimley

I'm a solo developer building Brimley, a profit analytics tool for Etsy sellers. Public launch around January 2027. Live now: a free standalone fee calculator and a Chrome extension version that shipped this week.

The motivation. Etsy gives sellers two top-line numbers — Shop Stats Revenue and 1099-K Gross. Neither matches what hits the bank. Etsy's API returns one aggregated `amount_fees` field combining listing fee, transaction fee (6.5% on item + shipping), payment processing (3% + $0.25 in US), Offsite Ads (12-15% capped at $100/order), currency conversion (2.5%), and country-specific regulatory fees. To see the breakdown you have to reconstruct each component using Etsy's documented formulas.

What's live (all free):
- Standalone calculator covering 24 countries: getbrimley.com/etsy-fee-calculator
- UK sub-page modeling 20% UK VAT-on-fees most calculators miss, with reverse-charge toggle for VAT-registered sellers: getbrimley.com/etsy-fee-calculator/uk
- Chrome extension (side panel, Manifest V3, minimum permissions, zero data collection): chromewebstore.google.com/detail/brimley-%E2%80%94-etsy-fee-calcul/ljhjmmbdmiiagkoihdkmngggnlnpnaei
- 4 research articles on fee mechanics, the Offsite Ads $10K trapdoor, deposit-vs-dashboard reconciliation, and Schedule C tax mapping: getbrimley.com/blog

Tech: Next.js 15, Supabase, Drizzle, Inngest, Resend, PostHog, Vercel. Extension uses Vite + React + crxjs/vite-plugin, calc engine reused via path alias to main app's lib/etsy-fees (single source of truth). 22/22 vitest tests on fee math.

Anti-positioning: not all-in-one. No keyword research, no AI listing optimization, no LLM in product logic. Just profit math, done well, with full drill-down to source transactions. Complementary to eRank/Marmalead/Alura, not replacing them.

Happy to answer questions about Etsy fee structure (the OA $10K lifetime trapdoor is genuinely surprising), why "just download the CSV" doesn't actually work, or technical questions about the stack.