Scrobble Time Machine

Your Last.fm history meets Spotify playback. An endless radio of your own past.

Use it: https://stm-lastfm.vercel.app/ (bring your own Spotify app, see Getting started)

What it does

Scrobble Time Machine connects your Last.fm scrobble history with Spotify playback. Start an endless radio of your own scrobbles: random songs from any year, or whole moments played back in the order you played them, so you hear exactly what you were listening to months or years ago.

Features

• Stations - pick Library (below), Discover (new music from Last.fm's recommendations and artists similar to your recent top artists, skipping songs you played or saved) or Mix (your past and new music, alternating)
• Library Radio - one click starts an endless stream from your own history; songs you played more often come up more often. Two options:
  • How it plays: Songs (random scrobbles, each from a different day) or Moments (a stretch of what you played back then, in the order you played it; when it ends the radio jumps to another moment)
  • When: every year, or one year you pick
• This moment - while Moments plays, a panel says when it was ("Tuesday, March 11, 2014 · evening"), with Save this moment (a Spotify playlist named after it) and Next moment
• Up next and artist info - click a queued song to jump to it; the artist's Last.fm bio and your play counts for the artist and track
• Play on - pick a speaker or another device on your Spotify account; a running radio moves with its queue, and on a computer the volume slider sets the speaker's volume
• Pick it up on your phone - start a radio on the computer, open the app on your phone and tap Open radio
• Installable - add it to your phone's home screen like an app
• Embedded player - the Spotify Web Playback SDK plays in the browser; no other device needed
• Liked songs - a heart button saves or removes the current song in your Spotify Liked Songs

Getting started

Spotify only lets an app in Development Mode serve 5 people, so everyone brings their own Spotify app. It's free and takes about 3 minutes. The first screen walks you through it; here are the same steps.

You need: a Last.fm account with a public profile, and Spotify Premium (Spotify requires it to own a developer app and to play in the browser).

1. Create the app. Open the Spotify Developer Dashboard, log in with your Spotify account and press Create app. Any name and description will do.
2. Tick two APIs. Under Which API/SDKs are you planning to use? tick Web API and Web Playback SDK.
3. Add the Redirect URI. Paste https://stm-lastfm.vercel.app/ into Redirect URIs, press Add, then Save. It must match exactly, slash included. (The first screen shows the address to use, with a Copy button.)
4. Copy the Client ID. Open the app's Settings. The Client ID is at the top. You don't need the Client secret.
5. Paste it into Scrobble Time Machine, enter your Last.fm username and press Connect Spotify.
6. Optional: invite friends. In your app's User Management, add the name and Spotify email of up to 4 more people. They paste the same Client ID.

Your Client ID stays in your browser. It isn't a password: it only tells Spotify which app is asking. To switch apps later, open the Spotify menu in the header and choose Use a different Spotify app.

Troubleshooting

What you see	What to do
Spotify says INVALID_CLIENT: Invalid redirect URI	The Redirect URI in your Spotify app is not exactly the app's address (check https, the domain and the trailing slash)
Spotify says INVALID_CLIENT: Invalid client	The Client ID was mistyped, or the app was deleted: choose Use a different Spotify app and paste it again
"This Spotify account isn't on that Spotify app's user list yet"	Using a friend's app: they add your Spotify email under User Management. Your own app: sign in with the Spotify account that created it
"Spotify Premium is needed to play in this browser"	That account is not Premium; it can still play on another device where Spotify is open
Nothing works with your app anymore	The app owner's Premium lapsed: Spotify turns Development Mode apps off until it is renewed
"Spotify is limiting searches"	Spotify's rate limit for your app; wait the time shown

How it works

No build step, no dependencies. Everything runs in the browser (plain HTML, CSS and JS files), plus two small Vercel functions:

• api/lfm-station.js fetches Last.fm's recommended station for Discover (Last.fm does not let a browser fetch it directly; it needs no key, only your username)
• api/session.js keeps a small note per Spotify user, so a radio can be picked up on another device (needs an Upstash Redis store)

Sign-in is Spotify's PKCE flow with your own app's Client ID, so there is no client secret anywhere. The Last.fm API key in js/config.js is shared: it only names the app, and Last.fm answers for whichever public username is asked.

Privacy

• Your Spotify tokens, your app's Client ID and your Last.fm username stay in your browser (localStorage); Disconnect removes the tokens, and Use a different Spotify app also forgets the Client ID.
• The app reads only public data from Last.fm (your scrobbles and play counts).
• api/session.js keeps the running radio's song list and state under your Spotify user id for 12 hours, so another device can pick it up. Your token is sent to it only to ask Spotify who you are; it is never stored or logged.
• No analytics, no cookies, no other servers.

Self-hosting (optional)

You don't need your own copy to use the app. If you want one anyway:

以上為 README 的開頭部分。其餘內容請閱讀原文。 檢視完整 README ↗