Podcast chapter builder

From your edit’s markers to chapters every app reads.

Import the markers from your edit, or paste a list, and see whether Apple Podcasts, Spotify and YouTube will show them. Then write them into the episode MP3, your show notes, or a chapters file for your host. The MP3 is rewritten in your browser, audio untouched. Nothing is uploaded.

Start from your markers, or your episode

Marker export: Audition (Markers panel › Export Selected Markers to CSV), Reaper (Region/Marker Manager › Export), Final Cut (File › Export XML), Resolve (Timeline Markers to EDL) or Premiere (Export Markers CSV). Or a WAV or AIFF with markers in it, as Audition, Logic and Hindenburg export. GarageBand has no markers: type or paste the list below instead.

The episode MP3: gives its length, reads any chapters already in it, and lets you save it with the chapters written in.

Chapters

Episode length

Where each app reads chapters

Apple Podcasts reads them from the MP3’s ID3 tags (or an M4A’s header), from a chapters file linked in your feed, or from timestamps in the episode description. It asks for at least three, the first at 00:00:00, and suggests chapters of two minutes or more, no more than six an hour, with titles under five words.

Spotify reads timestamps in the description, or Podlove chapters in the feed for shows hosted elsewhere. Its pages don’t mention ID3 chapters. It needs at least three, the first at 00:00, and 30 seconds between starts.

YouTube reads description timestamps: at least three, from 00:00, each at least 10 seconds long.

So the description list is the one place all three look. The MP3 tags carry chapters to Apple, and to the apps that read chapters from the file itself.

How the MP3 is written

Chapters go in as ID3 CHAP frames with a CTOC table of contents, the standard way to put chapters in an MP3. The rest of your tags and artwork are kept, any chapters already in the file are replaced, and the audio after the tag is copied byte for byte. The output has been read back with ffprobe and mutagen, and its audio checked bit-identical to the original.