Cut a YouTube lecture into chapters.

№ 01  /  Why

From 2-hour lecture to 8-minute concept.

YouTube hosts more lecture content than any university library: full MIT semesters, Stanford CS sessions, Khan Academy walkthroughs, every TED talk ever recorded, and thousands of independent educators teaching everything from quantum mechanics to medieval Latin. The format works for delivery — sit through the lecture once. It fails for revision: you don't want to scrub through 90 minutes to find the 6-minute proof you forgot.

Cutting a lecture into chapters fixes this. Pull just the segment that covers Bayes' theorem, or just the part where the professor walks through the derivation, and you have a focused study clip — small, named, and fast to rewatch. Repeat for each topic and you've turned a single video into a structured course of 8–12 mini-lectures.

When a lecturer ships their YouTube upload with chapters set, AppsGolem reads that chapter list and surfaces every chapter as a one-click pick. Click a chapter, the start and end fill in, hit cut. Shift-click to add several chapters to the batch queue and cut them all as a ZIP. If chapters aren't set, you paste the URL and enter HH:MM:SS yourself — same result.

№ 02  /  Audiences

Three ways educators and learners use chapter cuts.

№ 03  /  Precision

Stop a few seconds before the tangent.

Lectures aren't tightly edited. Professors meander, reference homework you didn't get, take questions mid-explanation, or break for a cough. Frame-accurate trimming lets you stop the clip exactly when the topic ends — not three seconds later when the question about lab-due-dates begins. AppsGolem accepts HH:MM:SS, so you can paste timestamps you noted while watching: "explanation of recursion: 47:12 to 53:48."

Multiple short cuts from one lecture cost less than one long cut. The URL probe is cached for a week, so after the first cut, every additional segment from the same video starts instantly. A 90-minute lecture cut into 12 chapters takes maybe 5 minutes total: paste once, set 12 ranges, download.

Lecture audio matters more than visual fidelity — you need to hear the professor clearly. AppsGolem keeps the audio bit-perfect from the YouTube source (no audio re-encode, no compression artifacts on the dialogue). Video is re-encoded to H.264 at libx264 veryfast CRF 22 — visually transparent quality, and the resulting MP4 imports cleanly into Premiere, DaVinci, or Final Cut for further editing.

№ 04  /  Audio mode

Audio mode for walking and driving.

Most lecture content is functionally a podcast — a person explaining things. The visuals are often supportive (slides, whiteboard) but the audio carries 80% of the value. Export to MP3 instead of MP4 and your study clip becomes a podcast you can listen to while commuting, walking, or doing dishes.

The MP3 export uses the original audio bitrate — typically 128 kbps for older lectures, 192 kbps for newer ones. File size is small (1–2 MB per minute), which means a 90-minute lecture cut into 10 audio chapters fits in under 200 MB total. Easy to sync to a phone, easy to share via Drive or Discord.

When the visuals matter — slides with formulas, whiteboard derivations, graphs — pick MP4. Both formats preserve the same precise trim, so you're not picking quality, you're picking destination.

№ 05  /  FAQ

Lecture cutting FAQ.