WebM Compressor – Online & Free

Upload your files to the online WebM compressor, change the quality and/or the bitrate, and then export your compressed WebM file. When using online compressors, you can lower the file size by lowering the video bitrate, by reducing the WebM video resolution (for example from full 1920 × 1080 to 1280 × 720), or by trimming the file length. The above-mentioned file size reducer is browser based, thus you don’t have to install anything to compress WebM online for free. Use this tool just for a single time to reduce the size of your video files quickly. If you frequently need to reduce WebM size, use local software.

Some WebM video compressors have a target file size field that they use to compute the bitrate required to reach that file size at the chosen resolution. If a tool does not have a target file size field, you can do a rough estimate of the required bitrate as follows: divide the target file size in MB by the length of the video in seconds and then multiply by 8 to get the bitrate in Mbps. Note that aggressively reducing the size of a video will degrade quality, especially in videos with fast motion or lots of fine detail.

Yes, it is safe. Just make sure the online WebM video compressor has HTTPS with encrypted file transfer and check the data retention policy. Most online compressors delete the files uploaded by users as soon as possible, usually within a few hours. That is why it is best to use online tools to process only public files, i.e. files that the user does not want to keep secret and that do not pose any danger to others.

For WebM files, typically the VP8 and VP9 encoders are used. VP9 is very efficient and delivers similar quality at 30% – 50% lower bitrate than H.264 encoders. Here are some practical starting points for bitrates when exporting WebM files with the VP9 encoder.

• 1080p: 4–8 Mbps
• 720p: 2.5–5 Mbps
• 480p: 1–2.5 Mbps

For VP8 you can add 30%–40% to the numbers for VP9 to get comparable quality, so for example for 1080p 4–8 Mbps VP9 would be comparable to 5–11.2 Mbps for VP8. This makes re-encoding a WebM file from VP8 to VP9 one of the best ways to shrink a WebM file without significantly reducing quality.

Audio quality could suffer, depending on the file size reducer, if audio bitrate is reduced in addition to video. A typical amount for transparent quality for stereo audio is 128 kbps Opus, audio encoded into a WebM file. 96 kbps would be sufficient for voice or very low complexity audio. Below 64 kbps will introduce noticeable artifacts. Be cautious if a WebM file size reducer has an independent control for audio or if it is tied to an overall quality setting. Lowering quality for very small files could result in very poor audio.

Web encoded with open-source video and audio codecs (VP8 and Ogg or Opus), WebM files are best for web delivery. Because of its open-source status and the fact that its files play back natively in Chrome, Firefox, and Edge without requiring any browser plugins. On the other hand, MP4 files (which contain H.264 video) are supported by a broader range of software than WebM files, including Safari, mobile devices, and other. For embedding a video on a website and controlling playback with a player, the VP9-encoded WebM file will generally be smaller than an MP4 file playing back the same quality video. However, for distribution of a video to play back on a variety of devices and via a variety of software players, MP4 is the safer choice.