What Is B-Roll? (And How to Make It With AI)

B-roll is the supporting footage that plays over your main shot — the scenery, close-ups, and cutaways that make a video feel finished instead of flat. If your "A-roll" is a person talking, your b-roll is everything you cut to while they talk. Here's what it is, why every good video uses it, and how to make exactly the b-roll you need with AI instead of hunting stock libraries.

TL;DR

B-roll = secondary/cutaway footage that supports the main footage (a-roll). Establishing shots, hands typing, product close-ups, scenery.
Why it matters: it covers edits, illustrates what's being said, sets the scene, and holds attention — the difference between amateur and polished.
Where to get it: shoot it, buy stock, or generate it with AI — describe the exact shot and create it on demand.
AI b-roll cost: a 5-second 720p clip is ~300 credits on Seedance 2 (~150 if you animate a photo).

A-roll vs B-roll: main footage versus the supporting cutaways

What is b-roll?

B-roll is any footage that isn't your primary shot. The term comes from old film editing: the "A-roll" held the main scene, and a second reel — the "B-roll" — held supplemental footage to cut in.

In a modern video, a-roll is the core content: the person speaking, the interview, the product demo, the narration. B-roll is everything you cut away to while that continues — a wide shot of the location, hands on a keyboard, a product turning on a table, a city street at dusk. The a-roll carries the message; the b-roll shows it.

Why b-roll matters

It covers cuts. When you trim a sentence out of an interview, the picture jumps. Lay b-roll over the join and the cut disappears.
It illustrates the point. Saying "our coffee is sourced from small farms" while showing a farm lands harder than a talking head alone.
It sets the scene. An establishing shot tells the viewer where they are in one second.
It holds attention. Cutting between a-roll and b-roll keeps the frame changing, which keeps people watching.

Videos without b-roll feel static and amateur. Videos with the right b-roll feel produced.

Where to get b-roll

Shoot it yourself — full control, but time-consuming and you need the location/subject.
Stock footage libraries — fast, but you're searching for a clip that's "close enough," it may be watermarked or paid, and everyone else uses the same clips.
Generate it with AI — describe the exact shot you need and create it. No shoot, no stock hunt, and it's unique to your video.

That third option is what's changed: you're no longer limited to footage that already exists.

How to make AI b-roll

AI b-roll is a perfect fit for text-to-video, because b-roll is usually a simple, specific shot — exactly what these models do well. On seedance-21.app:

Describe the shot you need like a director: subject, action, camera. "Close-up of coffee beans pouring into a grinder, slow motion, warm light."
Set 9:16 or 16:9 to match your timeline, pick the length, and check the cost (the credit cost shows before you run).
Generate, then drop it into your editor over the a-roll. If you already have a photo of the subject, animate it instead (image-to-video, ~150 credits).

A 5-second 720p clip runs ~300 credits on Seedance 2, or ~210 on the cheaper Fast/Mini tier for quick filler shots. Because failed generations aren't charged, you can iterate the shot until it fits. New accounts start with free credits. Generate a b-roll clip →

Prompt ideas for common b-roll:

Establishing: "aerial shot over a coastal town at sunrise, slow push-in."
Product: "a watch rotating on a marble surface, studio lighting, shallow depth of field."
Texture/filler: "rain on a window at night, soft focus, city lights behind."

FAQ

What does b-roll mean?
It's supplementary footage cut in over the main shot (a-roll) — cutaways, establishing shots, and close-ups that support the story.

What's the difference between A-roll and B-roll?
A-roll is your primary footage (the person talking, the main action). B-roll is the supporting footage you cut away to.

Can I generate b-roll with AI?
Yes. Text-to-video tools like Seedance 2 generate a specific shot from a prompt — ideal for b-roll, since you describe exactly the cutaway you need (~300 credits per 5-second 720p clip).

Is AI b-roll better than stock?
It's more specific — you get the exact shot instead of the closest stock match, and it's unique to your video. Stock is still faster for very generic shots.

How long should b-roll clips be?
Usually 2–5 seconds each in the edit; generate short clips and trim to taste.