Offline ConverterWhy is my .MOV file so big?
Three minutes of video. 1.2 gigabytes. Meanwhile a 90-minute movie you downloaded is 800 MB. Nothing is broken — you're just looking at footage that was never compressed for delivery. Here's what's actually going on, and how to fix it.
The three usual culprits
Frame rate and resolution. 4K at 60 fps is roughly eight times the data of 1080p at 30 fps. If you filmed in the iPhone's “4K/60” or “ProRes” mode, the size is expected behaviour, not a bug.
The codec. A finished MP4 you download uses H.264 or H.265 tuned for small size. A camera or screen recording often uses ProRes or Motion JPEG, which are edit-friendly formats that deliberately keep every frame fat so scrubbing stays instant. ProRes runs around 1.5 GB per minute at 4K.
Screen recordings. macOS records the screen essentially losslessly. A ten-minute screen capture at Retina resolution regularly lands over 2 GB even though it's mostly a static window.
How to check which one you've got
Right-click the file → Get Info, and look at the dimensions and codecs line. 3840 × 2160 means 4K. If the codec says “Apple ProRes 422” you're looking at an editing format, and converting it to H.264 alone will cut the size by 90% or more with no visible difference for anything that isn't going into colour grading.
Shrinking it
For a one-off, QuickTime's File → Export As → 1080p is enough and costs nothing.
When you need control — a target size, keeping the audio untouched, converting 40 clips from a shoot in one pass — that's what a real converter is for. Convert ProRes to H.264 (or H.265 for another ~40% saving), keep the resolution, and the 1.2 GB clip typically lands between 60 and 120 MB while still looking correct on any screen.
Keep the original if the footage is going into an edit. Convert a copy for sending.
Common questions
Is MOV bigger than MP4?
Not inherently — MOV and MP4 are containers, not compression. The same H.264 video is the same size in either. MOV files are usually bigger in practice because Apple devices and editing software write ProRes or lightly-compressed footage into them.
Will converting MOV to MP4 make it smaller?
Only if the codec changes. Re-wrapping ProRes into an MP4 container saves nothing; re-encoding to H.264 or H.265 is what cuts the size — often by 90% from ProRes.
Does compressing lose quality?
Some, always — but from ProRes or a screen recording the loss is genuinely invisible outside a grading suite. The visible losses come from cutting resolution or pushing the bitrate very low.