How to Get OBS to Capture Screen at the Correct Size

Getting OBS Studio to record or stream at the right resolution is one of those things that looks straightforward until it isn't. You open OBS, add a display capture source, and suddenly your output is cropped, stretched, letterboxed, or just the wrong dimensions entirely. Understanding why this happens — and what settings actually control it — makes the difference between a clean capture and a frustrating guessing game.

What "Correct Size" Actually Means in OBS

OBS works with two separate resolution settings that need to work together:

• Base (Canvas) Resolution — the working space OBS uses internally. Think of it as your virtual canvas.
• Output (Scaled) Resolution — the final resolution written to your recording or stream.

Your display capture source has its own native resolution too — whatever your monitor is physically running at. When these three values don't align, OBS scales, crops, or adds black bars to compensate.

The goal is to make these three things agree, or at least scale predictably.

Step 1: Match Your Canvas to Your Screen Resolution

The most common reason OBS captures at the wrong size is a canvas resolution mismatch.

To check and set your Base Resolution:

1. Open OBS → go to Settings → Video
2. Find the Base (Canvas) Resolution field
3. Set it to match your monitor's native resolution (e.g., 1920×1080, 2560×1440, or 3840×2160)

You can find your monitor's resolution in Windows under Display Settings → Display Resolution, or on macOS under System Settings → Displays.

If your canvas is set to 1920×1080 but your monitor runs at 2560×1440, OBS will either crop the capture or scale it down automatically — neither of which gives you a clean, accurate result.

Step 2: Fit Your Capture Source to the Canvas

Adding a display capture source doesn't automatically size it to fill the canvas. If the source appears smaller than the canvas, or is offset, you'll see black bars or a partial capture.

To fit a source to the canvas:

• Right-click the source in the Sources panel
• Select Transform → Fit to Screen (or press Ctrl+F on Windows)

This scales the source to fill the canvas while preserving aspect ratio. If you want it to fill completely without preserving ratio, use Stretch to Screen instead — though this will distort the image if the aspect ratios don't match.

You can also manually resize by clicking and dragging the red handles around the source preview in the OBS canvas.

Step 3: Set Your Output Resolution

Your Output (Scaled) Resolution in Settings → Video is what actually gets recorded or streamed. This doesn't have to match the base canvas — OBS will downscale automatically — but it should be intentional.

Common output resolutions:

If you're recording a 4K display but want a 1080p output file, set canvas to 3840×2160, capture your screen at native size, and set the output to 1920×1080. OBS handles the downscale cleanly.

Common Problems and What Causes Them 🖥️

Black bars on the sides or top/bottom This usually means your source and canvas have different aspect ratios. A 21:9 ultrawide monitor captured on a 16:9 canvas will always produce black bars unless you crop the source or change the canvas ratio.

Capture appears zoomed in or cropped Often caused by a canvas resolution smaller than the monitor resolution. OBS captures the full screen but the canvas can't display all of it.

Blurry or soft output Happens when the output resolution is set lower than the canvas without a matching downscale filter. In Settings → Video, try changing the Downscale Filter to Lanczos for better quality.

Source doesn't fill the preview The source dimensions and canvas dimensions don't match. Use Fit to Screen or manually drag the source to fill the canvas area.

Multi-Monitor and High-DPI Considerations

If you're on a HiDPI or Retina display (common on Macs and some Windows laptops), your OS may report a scaled resolution rather than the physical pixel count. For example, a MacBook with a 2560×1600 panel might be set to display at 1280×800 in macOS scaling terms.

OBS captures at the logical resolution the OS reports — not the raw pixel resolution. So setting your OBS canvas to 1280×800 in this case would be correct, not 2560×1600.

On Windows with display scaling above 100%, similar behavior applies. If captures look oversized or offset, check whether Windows scaling is affecting how OBS reads the display dimensions.

For multi-monitor setups, OBS lets you choose which display to capture. Each display can have its own resolution, so make sure the canvas resolution matches the specific monitor you're capturing — not your primary display if that's a different size. 🎯

The Downscale Filter and Framerate Add Another Layer

Even when resolution is correct, framerate mismatches between your monitor's refresh rate and OBS's output FPS setting can affect capture smoothness. The FPS setting lives in the same Settings → Video panel and is independent of resolution.

Additionally, if you're using Window Capture instead of Display Capture, the application window's own resolution and scaling settings come into play — a windowed app running at a non-standard size may need manual source resizing inside OBS.

What the right configuration actually looks like depends on your monitor's resolution and aspect ratio, whether you're on a HiDPI display, what you're capturing (full display vs. a single window), and whether your priority is file size, stream quality, or pixel-perfect accuracy. Each of those factors pushes the optimal settings in a different direction — and your specific combination of them determines which approach actually fits your setup. 🔍