Why Did My Video Get Bigger After Compressing?
Because you asked for a higher bitrate than the file already had. A compressor does not know what your source "should" weigh — it encodes to the settings you gave it, and if those settings are more generous than the original encoding, the result is a larger file that looks no better.
The usual causes
- The source was already compressed. A WhatsApp download, a re-uploaded clip or an old web video may already be at 800 kbps. Encoding it at "High quality" can ask for 5,000 kbps, and the encoder will dutifully spend them.
- A fixed bitrate above the source's. Setting 8 Mbps on a 3 Mbps file guarantees growth.
- H.265 to H.264. H.264 needs roughly a third more bitrate for the same quality, so this conversion enlarges the file by design. Correct when you need compatibility; surprising if you expected a saving.
- Upscaling. Encoding a 720p source at 1080p invents pixels and pays for them.
- A very short clip. Container headers and the first keyframe are a fixed cost that a two-second file cannot amortise.
How to avoid it
Look at the source bitrate before you choose settings — this tool shows it as soon as you pick a file. Then either:
- Use target size and name a number below the current size. Arithmetic cannot grow it.
- Or use constant quality at a CRF that is genuinely below the source's effective quality, and reduce the resolution at the same time.
This tool warns you before it starts when the planned bitrate exceeds the source's, because that is a minute of your time about to be wasted.
When there is nothing left to take
Some files are already efficiently encoded, and the only way to make them smaller is to accept visibly less: fewer pixels, fewer frames, or lower quality. If a 40 MB clip is a well-encoded minute of 1080p30, there is no clever setting that makes it 10 MB and still look the same. At that point the honest choice is downscaling — or sending a link instead of a file.
Reduce a video's file size → Runs in your browser. Nothing is uploaded.