Video too big to send? Four compression methods (online / software / mobile)
WeChat caps files at 100MB and email at 25MB — I have hit both. I tried four ways of compressing the same 98MB travel clip and the size and quality differences were large.
I tried to send a New Year trip video to the family group chat. The original was 98MB, WeChat spun for three minutes and finally said "file too large" — a video too big to send. I hit this at least four times a year.
The usual limits: WeChat allows about 100MB per file (a little more on desktop), email attachments stop at 25MB, and some OA systems are stricter. Douyin says 4GB, but big files upload slowly and eat up phone storage. Compression is not optional; it is a requirement.
Four compression methods
Method 1: in the browser (recommended)
Open Compress Video, drop the file in, pick a CRF level (a higher number means a smaller file), then download it. TwoThink processes it with ffmpeg.wasm in your browser, so nothing is uploaded.
My 98MB travel clip came down to 22MB at the standard level, faces were still recognisable, and WeChat accepted it on the first try.
Method 2: tick "compress" when sending in WeChat
The chat window sometimes offers to compress the video before sending. Convenient, but not controllable: you do not know how much it compresses or how the quality looks, and it only works inside the WeChat ecosystem.
Method 3: a mobile app
The app stores are full of "video compressor" apps — some are free but show splash ads, others upload to the cloud by default. I am not comfortable with that for sensitive material (contracts, internal training).
Method 4: ffmpeg on the command line
ffmpeg -i input.mp4 -c:v libx264 -crf 28 -preset veryfast -c:a aac -b:a 128k output.mp4
That gets the file down to about 18MB with decent quality; the catch is that you have to set up an environment, and colleagues will not manage it.
Measured comparison (the same 98MB H.264 travel clip)
| Method | Output size | Subjective quality | Privacy | Time |
|---|---|---|---|---|
| TwoThink online CRF28 | ~22MB | ★★★★ | ★★★★★ | ~40s |
| WeChat compress on send | ~35MB | ★★★ | ★★★ | fast |
| Some free app | ~28MB | ★★★ | ★★ | slow + ads |
| ffmpeg CRF28 | ~18MB | ★★★★ | ★★★★★ | fast locally |
The differences come from the encoding preset and whether the audio bitrate is touched. For scenes with a lot of motion, do not push CRF too hard or it turns into mosaic.
How to choose
- Occasionally sending over WeChat: use Compress Video, drop it in and pick the standard level — that is enough.
- You need it even smaller: try CRF 30, or Trim Video the useless intro and outro away first and then compress.
- An animation will do: if you only want to share a reaction, make a short Video to GIF — the file is tiny (see How to keep a video-to-GIF sharp).
- Wrong format: some devices produce MOV files that other people cannot open, so Convert Video Format to MP4 first and then compress.
My advice
Keep the original before you compress. Send a "preview version" out, keep the master for archiving. My routine now is: back up the original to the NAS → compress one WeChat-friendly copy online → if it is still too long, lower the resolution rather than pushing CRF ever higher.
Try it → Open Compress Video, drag in the file that would not send, and see whether the size drops below 100MB in one pass.