How to summarize a presentation (without copying the slides)

If you want to know how to summarize a presentation from class, start here: copying the slides in smaller handwriting isn't it. A lecture deck already is a summary, the one your professor made to support what they said out loud. Copy it and you end up with the same list of loose keywords, just in your own handwriting, and a summary you can't follow without the lecture is useless.

What does work is different: group the slides by topic, rebuild what's missing between the lines, and write it in your own words without looking. What you get is a page (or two) that reads like prose and that you can study during finals week without opening the PDF again.

Here's how I do it as a final-year computer engineering student, with a real example: the TCP lecture from my Networking course, sixty-odd slides that I first tried to summarize by copying the headings, which left me with a page that said nothing.

Why copying slides isn't summarizing

A slide has a heading, three or four lines and sometimes a diagram. In the lecture that's enough, because the professor connects the ideas, gives the example and explains why it matters. When you copy it into a notebook, you only copy what was written, which is exactly the part that explains the least.

Copying has two more problems:

• It feels productive and isn't. Filling pages feels like studying, but your brain didn't have to decide anything. It just moved text from one place to another.
• It follows the wrong order. The deck goes slide by slide, and the exam goes by topic. A concept introduced on slide 8 and used again on slide 41 ends up split across two places in your summary.

Step 1: skim the whole deck and mark the topics

Before writing a single word, flip through every slide in ten minutes. Not to learn anything, just to see the map: how many topics there are, where each one starts, and which slides are just the title page, an outline or an example.

The TCP lecture came down to four blocks for me: what TCP is for, how a connection opens and closes, how it makes sure data arrives, and flow and congestion control. Four headings on a blank page. That's the skeleton of the summary, and it isn't "sixty slides" anymore. It's four topics.

One tip: if the deck has an outline slide at the start, use it, but don't trust it completely. Often it's the course syllabus rather than what was actually covered that day.

Step 2: group slides by topic, not by number

Now go back to each block and write down which slides belong to it: "connection: 12 to 23, plus 47". That last part happens more than you'd think. Professors come back to a topic later with an example or a clarification, and that stray slide is often the one that explains the most.

Slide numbers don't index anything; topics do. By the end of this step, each topic in your summary pulls together everything the deck says about it, wherever it appears.

Step 3: rebuild what the professor said

This is the step almost nobody does, and the one that changes the result the most. For each group of slides, ask yourself: if this is what they wrote, what did they explain out loud?

A few clues for rebuilding it:

• A single word is a concept that needs a definition. If the slide just says "three-way handshake", the lecture explained what it is and why it takes three messages instead of two. Write that down.
• An arrow is a relationship. An arrow from A to B is a "because", a "so" or a "turns into". Say which one.
• A diagram is a story in order. Tell it in steps: first this happens, then this, and it ends up like this.
• If there's no example, make one up. If you can't think of one, you don't understand it yet, and it's better to find out now.

For whatever you can't rebuild, use your notes, the textbook or a classmate. If you missed that lecture entirely, what I wrote in missed a lecture: how to catch up will help.

Step 4: write it in your own words, without looking

Once the topic is clear, close the deck and write the summary for that block from memory, as if you were explaining it to someone who skipped class. Only then open the slides and fix what's missing or wrong.

It feels slower than copying, but it does two things at once. Writing without looking is active recall, one of the most effective ways to study (I covered it in active recall). And the gaps show up on their own: if you can't write how a connection closes, that's what you need to look at again.

My first summary of the connection block said roughly: "Before sending data, both sides agree using three messages: SYN, SYN-ACK and ACK. It lets each side know which sequence number the other one starts from." Two sentences. When I checked against the slides, I realized I'd forgotten about closing the connection, which works differently, and I added it.

A few rules that help me when writing:

• Full sentences, not keywords. If you just write "ACK", a month from now you won't know what you meant.
• One example per topic. Your own, not the one on the slide, if you can.
• Mark what you don't understand. A question mark in the margin is worth more than a copied sentence that sounds good.

Step 5: cut it down to one page per topic

The first draft always comes out long. That's fine. Reread it the next day and cross out everything you already know without reading it. A good summary keeps only what you forget, not everything that was said.

What usually survives into my final version:

• The definitions the exam asks for, written precisely.
• The steps of each process, in order and numbered.
• The differences people mix up, side by side: TCP vs UDP, flow control vs congestion control.
• One or two questions per topic to answer without looking during exam week.

If you end up with a page per topic, you're on track. If you end up with fifteen, you went back to copying.

Tools that help (and what they won't do for you)

You can do all of this with pen and paper, and that's what I'd suggest at first. If you use a note-taking app, it helps to be able to write in blocks and reorder topics without rewriting everything.

You can also ask an AI to draft a summary, but do it after writing your own, not before: the effort of writing it is what makes it stick. And check every claim against the lecture, because a confident, wrong summary is worse than none.

When I built Filmina, the web app that explains my lecture slides out loud, one slide at a time, I gave it a summary that builds itself when you finish the lecture: it gathers what was explained on each slide and organizes it by topic rather than by slide number, and you can copy it as text to paste wherever you keep notes. It's described in the lecture summary. Even so, the summary that helps me most is still the one I write on top of that.

For what comes after the summary, actually studying the deck in depth, the full method is in how to study from lecture slides.

Frequently asked questions

How do you summarize a PowerPoint presentation?

Skim the whole deck to see how many topics it has, group the slides by topic and rebuild what the professor explained on each one. Then write each topic in your own words without looking, and correct it against the slides.

How long should a lecture summary be?

There's no fixed length, but one page per topic is a good benchmark. If your summary has nearly as many pages as the presentation, you probably copied instead of summarizing.

Is it better to summarize by hand or on a laptop?

Both work as long as you write in your own words instead of copying. By hand it's harder to copy word for word, which helps; on a laptop it's easier to reorder topics and fix mistakes. Pick the one you'll actually use to review.

Can I use AI to summarize my lecture slides?

It works as a draft or as something to compare yours against, but it doesn't replace writing it yourself. The benefit of summarizing comes from the effort of organizing and explaining the topic, and you still have to check that what the AI says matches what was covered in class.