How to Record Only Part of Your Screen in OBS

OBS has no "record this region" button. Snipping Tool has one, QuickTime has one, OBS does not — it has a canvas, and sources placed on that canvas, and you get a partial-screen recording by trimming a source down to the part you want.

That distinction matters more than it sounds, because cropping a source does not change what resolution OBS writes to the file. Skip that step and you get one of two disappointing results: a small region floating in a sea of black, or a small region stretched up to fill 1080p and looking soft. Both are avoidable, and both are why "I cropped it and it looks worse" is such a common complaint.

This page is about capturing a fixed rectangle of your display. If what you actually want is one application, wherever it happens to be on screen, that is a different tool — see how to record a specific window in OBS. A crop cannot follow a window that moves; a window capture cannot trim off the top half of the window.

Method 1: Alt-Drag (Fast, Approximate)

The quickest way to trim a source, and the right one when the exact pixel boundaries do not matter.

1. Add a Display Capture source (Sources → +) and pick your monitor.
2. Click the source in the preview so the red bounding box appears.
3. Hold Alt (Windows) or Option (macOS), grab one of the handles, and drag inward.
4. The edge turns green. Green means cropped. Repeat for each side.

To undo it: right-click the source → Transform → Reset Transform.

Alt-drag crops the scene item, not the source. If the same source appears in two scenes, each scene keeps its own crop — which is genuinely useful when you want a wide shot in one scene and a tight one in another.

The Same Crop, With Numbers

Alt-drag is imprecise. For exact values without leaving the transform system, right-click the source → Transform → Edit Transform (Ctrl+E). The dialog has numeric Crop fields for Left, Top, Right and Bottom, plus position and size, and it is far easier to nudge than a mouse drag.

Method 2: The Crop/Pad Filter (Exact, Reusable)

The filter is a different thing in an important way: it applies to the source, so every scene using that source gets the same crop, and the crop happens before any transform. If you want one canonical region used consistently across a project, this is the one.

1. Right-click the source → Filters.
2. Under Effect Filters, click + → Crop/Pad.
3. Enter values for Left, Top, Right, Bottom.

The field most people get wrong: these are insets, not coordinates. "Right: 400" means remove 400 pixels from the right edge, not stop at x=400.

To capture a specific box on a 1920×1080 display, the arithmetic is:

• Left = the x coordinate where your region starts.
• Top = the y coordinate where your region starts.
• Right = 1920 − (Left + region width).
• Bottom = 1080 − (Top + region height).

For a 1280×720 region starting at (320, 180): Left 320, Top 180, Right 320, Bottom 180. The Relative checkbox toggles between this inset behaviour and absolute positioning — leave it ticked unless you have a reason not to.

The Step Everyone Skips: Output Resolution

You have now cropped a 1280×720 region. Your canvas is still 1920×1080, so OBS is still writing a 1920×1080 file with your region sitting in one corner and black filling the rest.

There are three ways out, and they are not equivalent:

Resize output (source size) is the right answer most of the time. The one case where it is not: you need a specific delivery resolution — a 1920×1080 YouTube upload, say — and your region is smaller. Then you are choosing between upscaling and letterboxing, and upscaling from 1280×720 to 1080p is usually the lesser evil.

If you must upscale, set Settings → Video → Downscale Filter to Lanczos. It is meaningfully sharper on interface text than Bilinear.

This is the whole explanation behind why an OBS recording looks worse than the preview in cropped setups: the preview shows the canvas, the file shows the result of scaling it.

Cropping for Vertical Video

If the region is for a Short, a Reel or a TikTok, do it in this order or you will fight the canvas the whole way:

1. Settings → Video → Base (Canvas) Resolution → 1080x1920. Output the same.
2. Add your Display Capture. It will be far too wide for the canvas.
3. Crop it to the vertical strip you want using the Crop/Pad filter.
4. Transform → Fit to screen.

Setting the canvas first means every subsequent decision is made against the shape you are actually delivering. Setting it last means redoing all of them.

The honest caveat: you are cutting a 9:16 slot out of a 16:9 interface. Unless the application has a genuinely narrow column of content, most desktop software does not survive that crop, and the result is a video of one third of a UI. Applications with a sidebar, a chat panel or a form column work; spreadsheets and timelines do not.

Excluding a Second Monitor

A specific case worth naming, because the obvious approach is wrong.

If you have two displays and want to record only one, do not capture both and crop. Add a Display Capture and choose the specific monitor in its properties — OBS enumerates them separately. Cropping a combined capture wastes the encoder on pixels you are discarding, and on mixed-DPI setups the maths rarely lands where you expect.

Cropping is for excluding part of one display: the taskbar, a browser's tab strip and address bar, a docked panel, a second-monitor edge that bleeds into the capture.

What Cropping Cannot Do

Worth knowing before you build a workflow on it:

• The region cannot move. It is a fixed rectangle. If your cursor leaves it, viewers see nothing — a real problem when you click a menu that opens outside the box.
• It cannot follow a window. Move or resize the application and the crop stays where it was. That is window capture's job.
• You cannot zoom in and back out mid-recording without building two scenes with different crops and switching between them with a hotkey — workable, but you are now operating a live production while also presenting.
• It does not reduce encoder load much. OBS still captures the full display and then discards pixels. If your goal was performance, cropping is not the lever; OBS high CPU usage covers what is.

A Different Answer to the Same Problem

Step back from the mechanics for a second. Almost nobody wants a cropped rectangle for its own sake. They want the viewer to be able to read the thing they are pointing at — and cropping is just the only lever OBS offers.

It is a blunt one. You are permanently discarding context to make one area larger, deciding before you record which area will matter, and losing anything that happens outside the box.

Cubix Capture inverts that. It records the full workspace and moves a virtual camera around inside it, zooming toward wherever your cursor is working and pulling back when you move elsewhere, so the detail is legible without the context being thrown away. Target aspect ratios including 9:16 and 1:1 are set upfront and the framing follows them, and the space around a non-matching source is filled with a background rather than black. It runs on Windows and macOS, and the free Starter plan is enough to record the same region both ways and compare what a viewer actually sees.

If your requirement is genuinely a fixed rectangle — masking a second monitor, or blanking a region that must never appear — cropping in OBS is exactly right, and the Crop/Pad filter is the precise way to do it.

Keep Reading

• How to Record a Specific Window in OBS — isolating an application instead of a rectangle.
• How to Screen Record with OBS: The Simplest Guide — the four settings that matter, if you are starting from scratch.
• Why Does My OBS Recording Look Worse Than the Preview? — the scaling maths behind soft cropped video.
• OBS Best Settings for Screen Recording — canvas, output and downscale filter in full.
• How to Screenshot a Specific Area on Windows — when a still would have done the job.