How to make a commercial: structure, length and script

What a commercial is and what makes one work

A commercial is a short video ad made for people who were not looking for it. That is the big difference from almost any other brand video: nobody sits down to watch it, it shows up between other things and it has to earn attention on its own. That is why a good commercial has more in common with a well-told joke than with a company presentation.

A commercial that works comes down to five traits. One idea, not three: if you want to say a backpack looks good, is tough and is theft-proof, pick what matters most or make three pieces. An opening that stops the thumb or the channel surfing. The product or service in action, not described. The brand recognisable before the end, in case someone drops off halfway. And a close that says what to do next: visit the website, find the shop, order in the app.

There are commercials for TV, radio, cinema and social media, and the logic is the same in all of them. What changes is the length, the format and the role of sound. On social media, many people will watch with the sound off, so whatever matters has to come across through the image and on-screen text.

The parts of a commercial, with a real example

Almost every commercial, however short, follows the same four-beat structure.

The hook, the first two or three seconds: a strange image, a question, a problem the audience recognises. On YouTube many ads can be skipped after five seconds, so everything is decided there.

The build-up: the situation, the conflict or the demonstration. This is where you see what the thing you sell is for.

The payoff: the product steps in and solves the problem or changes the situation. If the build-up is well set up, nothing needs explaining here.

The close: the logo, the brand line and the call to action. It usually takes the last three to five seconds.

One of ours: for the launch of La Bunker, the anti-theft backpack brand from BCNapiedecalle, we made three commercials instead of one. Each told a different side of the product, but all three shared the same world: urban Barcelona, constant movement, urban music and street style, shot in recognisable locations around the city. Each piece kept to the one-idea rule and, together, they built the brand from day one.

How long a commercial should be

There is no mandatory length, but every medium has its habits. On TV the usual formats are 20 and 30 seconds, with 10-second cut-downs; in Spain, 20 seconds is the most common. Radio works in a similar range. On social media the platform decides: YouTube has 6-second ads that cannot be skipped, Reels and TikTok suit pieces of 15 to 30 seconds, and a website or a brand launch has room for a one-minute piece that tells something more calmly.

The practical move is to think not of one commercial but of a family of lengths cut from the same shoot. For the La Bunker campaign we edited three pieces of 60, 45 and 30 seconds, ready for social media and the website. For Dr. Pizza, in its campaign with Glovo, we went to the other extreme: videos under 10 seconds, because in a delivery app people scroll from one dish to the next without stopping and there is no time for more.

The underlying rule is simple. If the idea does not land in the shortest version, the problem is not the length, it is the idea. And if you have to choose, a short commercial done well beats a long one that feels long.

How a commercial script is written: story and shooting script

A commercial is scripted twice. First comes the story script: what happens and what is said, scene by scene, in plain prose. It lets the brand approve the story without having to picture shots. A good test is to read it aloud against a stopwatch: if it does not fit the time you have, there is too much text.

Then comes the shooting script, which turns all of that into production language. It is usually written in two columns, picture on one side and sound on the other, and each row is a shot with its number, its type (wide, medium or close-up), its rough duration, what is heard and any on-screen text. It is what the shoot is planned from, and it tells you how many locations, actors and hours you need.

Many commercials add a third document, the storyboard: frames that sketch every shot and prevent surprises on the day.

Three tips repeat in every script that works. Write for the picture, not the voice-over: if something can be shown, do not say it. Put the brand in before the end. And cut the adjectives: there is no room in 20 seconds for innovative, unique and high quality, and they convince nobody anyway.

Step by step, and whether a phone, Canva or AI will do

The full process has five steps: goal and audience, idea, script, shoot, and edit with all its versions. We go through it phase by phase in what a campaign with a creative agency looks like, so here we focus on what people ask most: whether you can make one for free, at home, with Canva or with AI.

To test an idea, for a small business that posts every week or for a weekend offer, a template and a phone can be enough. The limit comes when the commercial has to represent the brand for months or compete with ads made by professionals: that is where light, sound, editing rhythm and, above all, the idea show.

Generative AI is similar. For Bunker's Christmas campaign we made two 30-second commercials with characters and sets created with AI, but with art direction, editing and post-production like any shoot. AI opened up a world that could not have been filmed; the idea and the finish were still people's work. We explain it in what works in an ad made with AI.

At Bostak Films we make commercials from start to finish, from the idea to the versions for each platform. If you have something to launch, tell us about it on our creative agency in Barcelona page.

FAQ

Got a project in mind?

We tell stories in video end to end — production, filming and post-production.

Keep reading