Cadence — Open-Source Follow-Up CRM in a Single HTML File
A complete CRM for freelancers and small businesses in one HTML file: weighted pipeline, follow-up engine, Excel import, statistics. Zero server, zero dependency, data never leaves the browser.
Overview
Cadence is a complete CRM that fits in a single HTML file. No server, no account, no dependency, no build step: open the file in a browser and it is installed. Data lives in the browser only, which makes GDPR compliance a property of the architecture rather than a promise.
The product thesis came from market research, not intuition: 80% of B2B sales close between the 5th and the 12th follow-up, yet 44% of salespeople stop after the first one. So Cadence is not a contact database with a pipeline bolted on. It is a follow-up engine. The home screen is not a dashboard: it is the list of who to follow up with today.
Key features
-
The morning list Overdue, today, tomorrow. Marking an action done logs it to the timeline and schedules the next one in a single keystroke. A "follow-up #3" counter reminds you most deals need five or more.
-
Weighted kanban pipeline Deal probability overrides stage probability, Pipedrive-style. Dormant deals are flagged per stage, with one improvement Pipedrive users keep asking for: a follow-up already planned within 7 days suspends the alert.
-
Quote cadence Moving a deal to "Quote sent" pre-fills follow-ups at day 3, 7 and 14. A followed-up quote converts at around 40% versus 15% without.
-
Excel-proof import and export Paste straight from Excel or Sheets: encoding detected, column mapping guessed, leading zeros of French phone numbers restored, mandatory preview. Exports ship with BOM and semicolons so Excel opens them cleanly, with formula injection neutralized.
-
Honest statistics Conversion funnel, monthly revenue, loss reasons. Every metric hides behind a data threshold instead of showing a misleading 0% or NaN.
Technologies used
- Vanilla JavaScript, HTML, CSS — no framework, no library, ~3,200 lines in one file
- localStorage with a versioned, sanitizing schema migration
- Inline SVG charts, palette validated by computation for contrast and color blindness
Challenges and learnings
The single-file constraint turns every "just add a library" reflex into a design decision. The hard parts were the ones users never see: a JSON import that cannot brick the app or inject HTML, CSV that survives Excel's opinions about phone numbers, date math that stays correct across timezones, and a full keyboard path with focus management.
The build process itself was part of the point: market research by parallel agents across ~50 sources, then an adversarial multi-agent code review that confirmed and fixed 40+ issues before release.
Outcome
A CRM a craftsman or freelancer can actually run their pipeline on, published open source with a live demo. It doubles as a proof of method: research first, opinionated product decisions, and a review process that treats a demo with the same rigor as production code.