Most tools stitch a long screenshot. Here is how to render a website scrolling as an MP4 instead, at the ratio your destination wants, with the same output every time.
Most tools that capture a long web page stitch it into one tall image. That is the right answer when you want a document. It is the wrong answer when you want to show a site moving — a scroll that reveals a layout the way a visitor would meet it, sized for a feed.
This is how to produce that: an MP4 of a website scrolling, at whatever ratio the destination wants, from a URL.
What you need
Aspects for macOS, and the address of the page. Nothing is installed in the browser and no extension is involved — Aspects loads the page itself, in a real WebKit view.
1. Load the page
Make a new Capture artboard and put the URL in. The page loads exactly as it would in Safari, because it is the same engine. Sign in, dismiss a cookie banner, scroll to the section you care about — whatever state you leave the page in is the state it renders from.
That last point is worth pausing on. Because Aspects drives a live page rather than a screenshot service, anything you can reach in a browser you can capture: pages behind a login, a staging URL on localhost, a design that only exists on your machine.
2. Choose the shape before you choose the motion
The ratio decides the composition, so set it first. Aspects names the destinations rather than making you remember numbers:
- 9:16 — Reels, Stories, TikTok, Shorts
- 4:5 — the Instagram and Facebook portrait feed
- 3:4 — Instagram's profile grid preview, which changed from square in 2025 and is what your post is cropped to on your own profile
- 1:1 — a square post
- 16:9 — YouTube, or anywhere a video is expected to be landscape
A desktop layout in a 9:16 frame is mostly empty margin. If the output is for a phone, set a narrower render viewport too and let the site's own responsive breakpoints do the work — you are capturing the mobile design, not shrinking the desktop one.
3. Build the scroll
Switch to Scroll mode. A scroll is a list of steps: go to this position, over this long, with this easing. Two steps is usually enough — rest at the top, then travel to the bottom — and a hold at either end stops the video starting and ending mid-motion, which is what makes a loop feel deliberate.
Easing matters more than duration. A linear scroll reads as machinery; an ease-in-out reads as a hand. If the page has a section worth dwelling on, add a step that stops there for a beat rather than slowing the whole thing down.
4. Export
Press export and you get an MP4. Not a screen recording of your desktop — there is no desktop in it, no cursor unless you asked for one, no dropped frames because another app woke up mid-capture.
Why the output is identical every time
This is the part that separates a rendered scroll from a recorded one, and it is worth understanding because it changes how you work.
A screen recorder samples whatever the display happened to show, at whatever rate the machine could manage. Render the same scroll twice and you get two different files: different frame timings, different dropped frames, a different result on a busy machine than on an idle one.
Aspects does not sample. Frame N is computed from the scroll position at frame N, with no reference to the wall clock at all. The same artboard produces the same bytes on a laptop on battery and a Mac Studio, today and next month.
Which means you can re-export at a different ratio, or after fixing a typo on the page, and get back exactly the video you had — minus the typo.
Common mistakes
Capturing the desktop layout for a phone-shaped video
The most frequent one. If the render viewport is 1440 wide and the output is 9:16, you are showing a wide layout letterboxed into a tall frame. Narrow the viewport and the site gives you its mobile design.
Scrolling too fast to read
A scroll that takes three seconds to cross a page nobody can read is an animation, not a demonstration. If the point is the content, slow down; if the point is the length, speed up and hold at the end.
Forgetting the first frame is the thumbnail
Whatever is at the top of the scroll is what people see before they press play. Start on something worth stopping for.
Where the file goes
Exports land in your Movies folder, and if cloud sync is on they appear on your iPhone within seconds — in the same folders you use on the Mac. That is usually the point: the video is for a feed, the feed is on a phone, and the file is already there when you get to it.