WebM Compressor

How to Compress WebM Files Online

1. Upload Your WebM Files: Drag and drop or click "Add Files" to select WebM clips. Screen recordings, downloaded web video, OBS captures, and Chrome MediaRecorder exports all work. Batch is supported — drop a folder of recordings at once.
2. Pick a Compression Mode: Choose Target file size (%) for predictable shrinkage (default 80%), Specific file size to hit an exact MB cap, Constant Quality to lock perceived quality with a CRF value, Constraint Quality for CRF with a bitrate ceiling, or Constant / Variable Bitrate for a fixed bps target. VP9 CRF is on a 0-63 scale — 23 is a sensible starting point per the WebM Project's encoding guide.
3. Resize, Trim, and Auto Scale (Optional): Use Auto Scale to let the encoder pick a resolution that hits the size target without manual math. Drop 1080p to 720p for screen recordings, set a Trim time range to cut intros and idle segments, or leave dimensions Unchanged. Cutting unused footage shrinks output more than any quality tweak.
4. Compress and Download: Click Compress. Files process on our servers and download individually or as a ZIP — no sign-up, no watermark, no file count limit.

Why Compress WebM Files?

WebM is Google's open container for the web — VP8/VP9 (or AV1) video paired with Vorbis or Opus audio, built on the Matroska container and announced in May 2010. It already ships smaller than equivalent MP4/H.264 by roughly 20-50% at matched quality, but raw screen captures, web downloads, and OBS recordings still routinely land at hundreds of MB. Common reasons to compress further:

• HTML5 video embedding — Self-hosted hero videos and product loops should stay under a few MB to avoid hurting Largest Contentful Paint. A 30 MB landing-page WebM at CRF 32 typically drops to 4-6 MB with no perceptible loss for muted background autoplay.
• Screen recordings from Loom, OBS, Chrome's Recorder — A 5-minute 1080p screen capture frequently comes out 80-300 MB. Re-encoding at CRF 30 with 15-24 fps (UI demos don't need 60 fps) often hits a 10-30 MB file that's emailable.
• Discord and chat uploads — Discord lowered the free-tier attachment cap from 25 MB to 10 MB in September 2024; Nitro Basic is 50 MB, full Nitro 500 MB. Compressing keeps you under the free cap without needing Nitro.
• Email and cloud limits — Gmail caps attachments at 25 MB. iCloud Mail and most providers sit at the same 20-25 MB band. Compressing a 90 MB screen-share down to 15-20 MB makes direct attachment possible.
• Cutting CDN bandwidth bills — High-traffic sites serving a 12 MB intro video pay real money on egress. A CRF 33 re-encode often drops to 2-3 MB with no visible difference on muted autoplay.
• Archiving older WebM downloads — Old yt-dlp / video saver outputs from before VP9-was-default can be re-encoded to VP9 at CRF 28-30 and shrink 40-60% with imperceptible quality difference at those settings.

Compression Mode Quick Guide

VP9 CRF Reference

WebM vs MP4 — Format Comparison

Frequently Asked Questions

How much can I shrink a WebM file?

Typical reductions are 30-70% at default settings and 70-90% with aggressive CRF (34+) or resolution drops. Screen recordings and UI demos compress much better than full-motion gameplay or live-action — large flat areas of static pixels (windows, code editors, slide decks) encode efficiently. A 200 MB 1080p screen capture often becomes a 15-25 MB CRF 30 file that's visually indistinguishable on first watch.

Should I pick Constant Quality (CRF) or Target File Size?

CRF is the better default — it locks perceived quality and lets the file size float, so you get consistent visual results across a batch. Pick Target File Size or Specific File Size only when you need to hit a hard cap (Discord 10 MB, Gmail 25 MB, a CDN limit). CRF 28-30 is a strong starting point for most web content; drop to 23-25 for archival, push to 33-36 for muted autoplay backgrounds.

What CRF value should I use?

For VP9, the scale is 0-63 (lower = higher quality). Per the WebM Project's official encoding guide, 23 is a reasonable default and a ±6 change roughly halves or doubles the file size. Tune from there: 20-23 for archival, 24-28 for product demos, 30-33 for chat/email shares, 34-38 for background hero videos. Note CRF in VP9 is resolution-dependent (unlike H.264), so the same CRF will look better at lower resolutions.

Will compressed WebM still play in every browser?

WebM (VP9) plays natively in Chrome, Firefox, Edge, Opera, and Safari 16+ (macOS) / iOS 17.4+, covering roughly 95-97% of browsers globally per caniuse. For older Safari users and Internet Explorer holdouts, serve an MP4 fallback in the same <video> tag — Chrome will pick WebM, older Safari will fall back to MP4. See also WebM to MP4 and MP4 to WebM.

Can I compress WebM to fit Discord's 10 MB free-tier limit?

Yes — pick Specific file size and enter 10 MB (or 9.5 MB to stay safely under). The encoder will auto-scale resolution and pick a bitrate to hit that target. Discord lowered the free cap from 25 MB to 10 MB in September 2024, so older guides showing 8 MB or 25 MB are out of date. Nitro Basic raises the cap to 50 MB and full Nitro to 500 MB.

Will compressing reduce the video's playback length?

No. Compression changes the size in MB, not the duration. The video plays back at the same length and frame rate unless you explicitly use the Trim time range to cut out segments, or reduce frame rate (e.g., 60 → 30 fps), which is sometimes useful for screen recordings.

What's the difference between VP8, VP9, and AV1?

VP8 is the original WebM video codec (2010) — broadly compatible but ~30-40% larger than VP9 at matched quality. VP9 (2013) is the practical default — strong compression, hardware decoding on most 2018+ devices, and supported in 95%+ of browsers. AV1 (2018, AOMedia) is roughly 30% more efficient than VP9 but encoding is 5-10× slower and decoding requires 2022+ hardware for smooth playback. For most web compression today, VP9 is the sweet spot.

Can I trim and compress in one pass?

Yes. Set Trim to a time range to cut intros, idle moments, or post-credits. Cutting unused footage is the most effective single change you can make — removing 30 seconds of dead air from a 2-minute screen recording cuts the output 25% before any CRF or bitrate tuning. Combine trim with CRF 30 for a typical 70-85% total reduction.

Are my files uploaded to a server?

Compression runs on our servers. Files aren't kept on a permanent server and there's no sign-up. For longer videos or low-power devices where server-based conversion is slow, see also MP4 compression or video trimming as a preprocessing step.