How to Compress Screen Recordings (OBS, QuickTime, Loom)

Screen recordings are simultaneously the easiest video to compress and the easiest to wreck. Easiest, because most of the pixels do not change between frames — a one-hour recording routinely shrinks by 80–90%. Easiest to wreck, because the moment you scale the picture down, the text stops being readable and the whole recording becomes useless. The rule is the opposite of the one for camera footage: keep the resolution and let the quality setting do the work. Drop your file into the browser compressor, leave the resolution at original, and you will usually get a file a fraction of the size that still looks pin-sharp.

Why screen recordings come out so huge

• Recorders default to quality, not size. OBS and QuickTime are built for people who will edit afterwards, so their defaults deliberately waste space. That is the right default and the wrong file to send anyone.
• They run long. Nobody records a 20-second screen capture. Demos, meetings and bug reproductions run 10 to 60 minutes, and size scales linearly with time.
• 60 fps by default. Screen recorders often capture at 60 fps because they are aimed at gameplay. A slide deck at 60 fps is pure waste.
• Some presets are effectively lossless. OBS's top recording quality and QuickTime's maximum-quality modes produce files measured in gigabytes per minute.

The settings that work for screen content

Two of these levers live in your recorder, and two live in the compressor. It is worth knowing which is which before you start fighting the wrong one:

Setting	Where	What to do
Resolution	Compressor	Leave at original. Text is the content — halving the resolution makes small UI labels unreadable. This is the one place where downscaling is not the free win it usually is.
Quality (CRF)	Compressor	24–26. Screen content compresses so well that you rarely need to go higher, and pushing past 28 starts putting visible ringing around letters.
Frame rate	Recorder	Record at 30 fps, not 60. Worth roughly a third of the file, and a cursor at 30 fps looks completely normal. This has to be set before you record — re-encoding will not undo a 60 fps capture.
Audio	Recorder	Keep it, but count it: output audio is 128 kbps, about 1 MB per minute. On a 60-minute recording that is ~57 MB before a single frame of video. If you do not need narration, record without it.

That last row explains a lot of frustrated attempts at hitting a small target. If a 45-minute walkthrough refuses to fit under 25 MB, it is not the compressor being weak — the audio track alone is most of the budget.

OBS Studio

OBS is the most common source of unnecessarily huge recordings, and it is entirely down to one dropdown. Under Settings → Output → Recording, the Recording Quality options escalate fast: "High Quality, Medium File Size" is a sensible CRF around 23, "Indistinguishable Quality" is roughly CRF 16 and several times larger, and "Lossless" produces files so big they are only useful as an editing intermediate.

• If you already have the file: drop it into the compressor as-is. OBS records to MKV by default and MKV is accepted directly — no remux needed first.
• If you want to fix it at the source: set Recording Quality to "High Quality, Medium File Size", and set your recording FPS to 30 under Settings → Video unless you are capturing gameplay.
• If you need MP4 rather than MKV: OBS's File → Remux Recordings rewraps the file without re-encoding it, so it is instant and lossless. Compressing with SqueezeVid also outputs MP4, so if you are compressing anyway you can skip the remux entirely.

QuickTime and macOS screen recordings

macOS screen recordings — whether from QuickTime Player or the Cmd+Shift+5 toolbar — come out as H.264 in a .MOV container at a generous bitrate. They are perfectly good files; they are just larger than they need to be and wrapped in a container that some upload forms and Windows recipients dislike.

Compressing one gives you both fixes at once: the output is an MP4 with the metadata at the front, so it streams and previews properly. Keep the original resolution — Retina captures are frequently 2880 or 3456 pixels wide, and while that is a lot of pixels, it is also why the text looks so good. If the file is still too big at native resolution, push the quality value up to 28 before you consider scaling anything down.

One thing worth knowing: QuickTime's New Movie Recording and export presets can be set to a maximum-quality mode that produces enormous files. If a two-minute capture is somehow a gigabyte, that is what happened.

Loom and other browser recorders

Loom downloads give you an MP4 that is already H.264, so compatibility is not the problem — size is. Browser-based recorders bias towards a high bitrate to keep text crisp, which is the right call while recording and unnecessary once you are sending the file to someone.

Two practical notes:

• Download the file, do not screen-record the player. Recording a playing video re-encodes it a second time and looks noticeably worse than compressing the download.
• Compressing a Loom download is safe and cheap. These files typically shrink 60–80% at CRF 26 with the resolution untouched, because the content is still mostly static UI.

Realistic numbers

Source recording	Settings	Typical result
OBS 1080p60, 30 min, ~2.5 GB	Original resolution, quality 26	~250–450 MB (−80–90%)
QuickTime Retina capture, 10 min, ~1.2 GB	Original resolution, quality 26	~120–250 MB (−80–90%)
Loom download 1080p, 15 min, ~400 MB	Original resolution, quality 26	~80–160 MB (−60–80%)
Slide-deck walkthrough 1080p, 45 min, ~1.5 GB	Original resolution, quality 28	~100–200 MB (−85–93%)

Screen recordings sit at the top end of what compression can do, because a slide that does not change for eight seconds costs almost nothing to encode. A recording of a video game, a scrolling page, or a full-screen animation will not do nearly as well — the more of the frame that changes, the more bits it needs.

When the file is bigger than your browser can handle

Long recordings get big. In-browser compression is bounded by your device's memory at roughly 2GB; above that, use the large video compressor, which handles files up to 10GB server-side and deletes them automatically after processing. For anything below 2GB, stay in the browser — nothing is uploaded, and a 30-minute recording does not have to travel anywhere before it starts compressing.

Frequently asked questions

How do I make an OBS recording smaller?

Two levers. Before recording, set Settings → Output → Recording → Recording Quality to "High Quality, Medium File Size" and record at 30 fps. After recording, drop the file — MKV or MP4 — into the compressor at original resolution with quality 26; a 1080p60 OBS capture typically loses 80–90% of its size.

Why does my screen recording look blurry after compressing?

Almost always because the resolution was reduced. Text has no tolerance for scaling: a 1080p recording shown at 720p turns UI labels into smudges. Keep the original resolution and use the quality value to save space instead — screen content tolerates a higher CRF far better than it tolerates scaling.

Can I compress an MKV recording without converting it first?

Yes. MKV files are accepted directly, and the output is an MP4 — so the compression and the container change happen in one step. You do not need to remux in OBS beforehand.

Why can't I get my hour-long recording under 25 MB?

Audio. At 128 kbps, an hour of sound is about 57 MB on its own, which already exceeds the target before any video is added. Either trim the recording, split it into parts, or share it as a link instead of an attachment.