How to Reduce a Video File Size Without Ruining the Quality

By Thiago · Updated September 25, 2026 · 4 min read

A one-minute clip from a modern phone can easily pass 100 MB. That is far too big for email and slow to upload anywhere. The good news: most of that size can go away with almost no visible difference, as long as you change the right things.

Why phone videos are so big

Phones record at a very high bitrate, the amount of data used for each second of video. A phone recording in 4K at 30 or 60 frames per second writes tens of megabits every second so it can capture every detail, even if you later watch it on a small screen. That is great for editing, but wasteful for sharing.

Three things decide how big a video file is:

• Length. Double the duration, double the size.
• Resolution. 4K has four times as many pixels as 1080p, and 1080p has more than twice as many as 720p.
• Compression level. How much detail the encoder is allowed to discard. This has the biggest effect of all.

What a video compressor actually does

A compressor re-encodes the video with more efficient settings. ConvertKiwi's video compressor uses the H.264 codec, the most compatible video format there is, and controls quality with a setting called CRF (constant rate factor). A lower CRF means better quality and a bigger file, and a higher CRF means a smaller file. Every step of about 6 roughly halves the file size.

You choose one of three levels:

The resolution limit applies to the height of the frame, and a video is never enlarged. A 4K clip on "Balanced" comes out at 1080p, while a 720p clip stays at 720p. Vertical phone videos keep their shape: the limit applies to the height, so they get proportionally narrower.

The result is always an MP4 file that plays on any phone, browser, TV and social network. It is also prepared for streaming, so it starts playing before it has fully downloaded.

Which level should you pick?

Sending by email

Most email services cap attachments at around 20–25 MB (Gmail's limit is 25 MB). Start with Smallest file. As a rough guide, a 720p clip at this level usually lands at a few megabytes per minute, depending on how much movement there is. If the result is still too big, trim the video first. Length is the one thing a compressor cannot change.

Chat apps and Discord

Messaging apps usually recompress videos themselves, often quite aggressively. Sending a file that is already reasonably small (Balanced or Smallest file) gives you more control over how it looks. Some platforms have strict limits for free accounts. On Discord, for example, the free upload limit is currently 10 MB.

Uploading to YouTube, Instagram or TikTok

These platforms re-encode every upload anyway, so feeding them a higher-quality file gives a better final result. Use Better quality or skip compression entirely if your connection can handle the original.

Archiving or backing up

Keep the original if you might edit the video later. If storage is tight, Better quality can shrink a phone recording a lot without a visible difference on most screens.

Why some videos barely shrink

• The video is already compressed. Files that came from WhatsApp, social media or a screen recorder are often already efficient. Compressing them again saves little, and it can cost some quality.
• Lots of motion. Confetti, water, fast sports or a shaky camera change every pixel in every frame, and that takes more data no matter what.
• Very short, high-resolution clips. Try the Smallest file level, which also lowers the resolution.

Other ways to make a video smaller

• Trim it. Cutting a two-minute clip down to the 30 seconds that matter cuts the size by 75% before any compression.
• Record at a lower setting. If you only share videos, 1080p at 30 fps is plenty. On iPhone, look in Settings → Camera → Record Video. On Android, look in the camera app's settings.
• Convert MOV to MP4. iPhone MOV files in the HEVC format are efficient but don't play everywhere. Converting MOV to MP4 fixes compatibility. If size is the goal, use the compressor, which produces MP4 directly.
• Send a GIF for short loops. For a few silent seconds of a reaction or a demo, an animated GIF may be all you need.

Step by step

1. Open the video compressor and add your video (MP4, MOV, WEBM, MKV, AVI or M4V, up to 100 MB).
2. Pick a level. If you're not sure, start with Balanced.
3. Click "Compress video". The progress bars show the upload, then the real encoding progress.
4. Download the MP4 and check its size. If it's still too big, run the original again on Smallest file.