How to Compress a Video to 10 MB or 25 MB (Without Uploading It)

A one-minute phone video is often 100 MB or more. That’s far over the limit for an email attachment, most online forms and many chat apps. This guide explains why videos are so large, how to work out what will fit, and how to compress one on your own device with the Video Compressor, without uploading it anywhere.

Why phone videos are so big

Phones record at a high bitrate: the amount of data used for each second of video. A 1080p clip from a recent phone often uses around 15–20 megabits per second (Mbps) with H.264 (less with HEVC), and 4K uses far more. The camera chooses quality over size, because it can’t know what you’ll do with the clip later.

The file size follows directly from the bitrate and the length:

File size (MB) ≈ bitrate (Mbps) × length (seconds) ÷ 8

So a 60-second clip at 16 Mbps is about 16 × 60 ÷ 8 = 120 MB.

Working backwards from a size limit

The same formula tells you what bitrate fits a limit. To fit 25 MB in 60 seconds:

25 × 8 ÷ 60 ≈ 3.3 Mbps in total for picture and sound

That’s comfortable for sharp 720p and borderline for 1080p. For 10 MB in 60 seconds, the budget drops to about 1.3 Mbps, which looks much better at 540p than at full 1080p. A sharp smaller picture looks better than a blocky large one.

Length	Under 10 MB	Under 25 MB
30 seconds	~2.6 Mbps: 720p	~6.6 Mbps: full 1080p
1 minute	~1.3 Mbps: 540p	~3.3 Mbps: 720p
3 minutes	~0.4 Mbps: 360p	~1.1 Mbps: 540p
10 minutes	~0.13 Mbps: 240p, barely watchable	~0.33 Mbps: 360p

These are the resolutions the Video Compressor picks on Auto for a 1080p video; the bitrates are before the small overhead of the file format. If your video is too long for the size you need, trim it first and send only the part that matters.

Compress a video in your browser

1. Open the Video Compressor and drop in your video (MP4, MOV, WebM or MKV).
2. Leave Target size selected and pick the limit: 10 MB, 25 MB or another size.
3. Leave Resolution on Auto. The tool works out the bitrate from your video’s length and lowers the resolution if full size would look blocky.
4. Click Compress video and keep the tab open until it finishes.
5. Play the result, then download the MP4.

Video encoders never hit a bitrate exactly, so the tool measures the result. If it came out over the limit, it compresses again at a slightly lower bitrate, up to two more times. If a video simply can’t fit, for example a 15-minute recording into 10 MB, it tells you the smallest size that works instead of producing an unwatchable file.

For the two most common limits there are ready-made pages: compress video to 10 MB and compress video to 25 MB.

Why it doesn’t upload your video

Most online compressors make you upload the whole file to their server first, which takes ages on mobile data and hands your video to someone else. OptiPress compresses in your browser using its built-in video encoder (WebCodecs), which on many phones and computers runs on the device’s own video hardware. A one-minute clip usually takes well under a minute, and the video never leaves your device.

A few tips

• Email limits count the encoded size. Gmail’s limit is 25 MB, but attachments grow when they’re encoded for sending, so a file close to 25 MB may be refused or turned into a Drive link. Aim for 16–20 MB to be safe.
• 60 fps becomes 30 fps. Frame rates above 30 are reduced, which saves a lot of space and looks the same for most clips.
• Already small? If a video is already under your limit, the tool says so. Compressing it further still works, but there may be little to gain.
• Need just the sound? Use Video to MP3: an audio file is a tiny fraction of the video’s size.