How to compress a video
A video's size is simply its bitrate multiplied by its length. Everything else, including resolution, frame rate and codec, decides how good the picture looks for that number of bits.
Why phone videos are so big
Phones record at high bitrates so the camera can encode in real time without visible damage: iPhones and recent Android flagships commonly write 1080p at roughly 15–20 Mbps and 4K at 40–60 Mbps or more. A careful encoder with time to think can get a near-identical picture from a fraction of that. That's why a 400 MB phone clip often squeezes to 40–60 MB without anyone noticing, while a video downloaded from YouTube barely shrinks at all: it was already squeezed.
How codecs save space
H.264 doesn't store 30 separate pictures per second. It stores an occasional complete keyframe, then for the frames in between it records only what moved and by how much, plus a small correction. A talking head against a wall is mostly "same as before", which is nearly free. Confetti, rain, water and camera shake change everywhere at once, which is why they fall apart first at low bitrates.
Between keyframes an encoder stores only what changed, so a static shot costs almost nothing while a moving one eats bits. The night sky changes on a slower schedule; ahaboo narrates why the Moon has phases.
Resolution is the lever people forget
When a file has to fit a size, the bitrate is fixed by arithmetic. The only question is how many pixels share it. Drag the bitrate below and compare how much data each pixel gets.
Bits per pixel per frame at each resolution. 1080p has 2.25× the pixels of 720p, so the same file size gives each pixel less than half the data. When a size limit is tight, a sharp 720p beats a smeared 1080p.
A practical order of operations
- Trim. Every second you cut saves bits at no quality cost.
- Choose the resolution for the screen it will be watched on. 720p for phones and chat apps, 1080p for laptops and TVs.
- Pick quality or size. With no hard limit, use CRF 23–27. With a limit, work out the bitrate in the bitrate calculator, or let the compressor do it.
- Consider the audio. 96–128 kbps AAC is fine for most video; for a silent screen recording, remove it.
- Drop to 30 fps unless it's gaming or sport footage recorded at 60.
For hard limits, the presets for Discord and email already build in a safety margin.
Questions people ask
How do I compress a video without losing quality?
Truly lossless video compression barely reduces size. What works is "visually lossless": re-encode with H.264 at CRF 20–23 and keep the resolution. Phone videos are recorded at very high bitrates, so they often shrink a lot with no visible change.
What is the best format for a small video?
H.264 in MP4 is the safest choice because it plays everywhere. H.265 (HEVC) and AV1 are smaller at the same quality but encode more slowly and don't play on every device.
How do I compress a video on iPhone or Android?
Open squeezefiles.com/compress-video in your phone's browser and pick the video. Encoding on a phone is slower than on a laptop, so short clips work best. Alternatively, set the camera to record 1080p instead of 4K.
Why is my compressed video bigger than the original?
The original was already efficiently encoded (for example, a video downloaded from a streaming site) and you asked for a higher quality or bitrate than it had. Pick a lower quality level or a target size below the original.