# Sprogeny

> Sprogeny (sprogeny.com) is a free web app that combines multiple Spotify playlists into a single weighted, truly random mix. Not affiliated with Spotify AB.

## What it does

Takes two or more Spotify playlists, lets the user assign a weight (ratio) to each, and generates a new playlist in the user's Spotify library — randomly shuffled with no play-count weighting, no algorithmic track promotion, no emotional weighting.

## Key features

- Combine any number of Spotify playlists
- Per-playlist weight sliders control track proportions
- Output playlist created directly in the user's Spotify library
- Source playlists are never modified
- Free, no ads, no tracking cookies
- Sign in with existing Spotify account via OAuth — no separate account needed
- No AI or recommendation algorithms involved in track selection

## How it works

1. User authenticates with Spotify via OAuth 2.0 (Sprogeny never receives the Spotify password)
2. User adds source playlists by pasting a link or selecting from their library
3. User adjusts weight sliders to set the mix ratio
4. User hits Generate; Sprogeny builds a weighted random shuffle and creates a new playlist via the Spotify API
5. The new playlist appears in the user's Spotify library immediately

## Privacy

- Session stored in encrypted cookie only
- Playlist and track data used in-memory during session, not persisted afterward
- Non-reversible hash of used tracks stored to avoid duplicates across combine operations
- Self-hosted cookieless analytics (Matomo) — no personal data, no third-party sharing
- Spotify permissions: playlist-read-private, playlist-read-collaborative, playlist-modify-public, playlist-modify-private

## Tech stack

SvelteKit 2, Svelte 5, TypeScript, Three.js, Spotify Web API, adapter-node

## Public pages

- https://sprogeny.com/ — Homepage
- https://sprogeny.com/faq — FAQ and privacy information
- https://sprogeny.com/terms — Terms of use

## What it is not

Sprogeny does not play music. It creates playlists in Spotify, which users play using the Spotify app. It is not a streaming service, Spotify alternative, or playlist management dashboard.