WebM to WebM Converter

How to Re-encode WebM Files Online

1. Upload Your WebM File: Drag and drop or click "+ Add Files" to load WebM files from your computer. Batch upload is supported — re-encode an entire folder of clips with the same settings in one pass.
2. Pick a Video Codec: Choose VP8 for maximum compatibility (every browser since 2010), VP9 for 50% smaller files at the same visual quality, or AV1 for the best compression available today (30% smaller than VP9). Audio Codec defaults to Opus — the modern WebM standard — but Vorbis is available for legacy players.
3. Tune Quality, Resolution, or Trim (Optional): Set a CRF value on the 0-63 scale for VP9/AV1 (lower = higher quality; 30-35 is a good web target), pick a Video Resolution Preset (144p, 240p, 360p, 480p, 720p, 1080p, 1440p, 2160p, 4320p), scale by percentage, or use Video Trim to keep only a specific start time and duration.
4. Re-encode and Download: Click "Convert" and your re-encoded WebM downloads in seconds. Files process in your browser session — no sign-up, no watermark, no upload to a third-party server.

Why Re-encode WebM?

WebM is a container, not a single codec. The same .webm file might be VP8 + Vorbis (the original 2010 spec) or VP9 + Opus (the modern default) — and now AV1 is showing up in newer encodes. Re-encoding the same WebM gives you control over codec, bitrate, resolution, and length without changing the container, which keeps the file playable everywhere a WebM is expected (HTML5 <video> tags, Chrome, Firefox, Discord previews, OBS recordings).

• Shrink an OBS or screen recording for upload — OBS records WebM at high bitrates by default. A 5-minute 1080p VP8 capture can be 400MB+. Re-encoding to VP9 at CRF 32 typically lands under 50MB while looking nearly identical.
• Switch from VP8 to VP9 or AV1 for storage savings — A 200MB VP8 clip drops to ~100MB at VP9 with the same quality, or ~70MB at AV1. Useful when archiving years of recordings or fitting more onto a 500MB cloud-storage tier.
• Hit Discord, Slack, or email size limits — Discord's free tier caps uploads at 25MB (Nitro Basic 50MB, Nitro 500MB). Gmail caps attachments at 25MB. Re-encoding lets you hit the limit without changing format.
• Downscale 4K WebM to 1080p or 720p — A 4K screencast or game capture is overkill for a tutorial that will be embedded at 720p anyway. Drop the resolution and you cut bitrate requirements by ~75%.
• Trim before publishing — Cut out the dead time at the start of a recording or extract a 30-second highlight from a longer clip. The Video Trim option saves only the segment you want, re-encoded cleanly without a black-frame transition.
• Strip audio or replace the audio codec — Some tools choke on Vorbis audio inside WebM. Re-encoding to Opus fixes playback issues in modern browsers and reduces audio bitrate overhead.

VP8 vs VP9 vs AV1 — WebM Codec Comparison

CRF Quality Guide for VP9 and AV1

Frequently Asked Questions

Why would I convert WebM to WebM instead of just keeping the original?

The output container stays .webm, but the codec, bitrate, resolution, and length inside can all change. A VP8 WebM at 1080p/8Mbps and a VP9 WebM at 720p/2Mbps are both valid .webm files but have wildly different sizes and playback characteristics. Re-encoding lets you change the inside without changing the file extension that downstream tools expect.

Should I pick VP8, VP9, or AV1?

Pick VP9 unless you have a reason. It's universally supported in browsers since ~2017, has hardware decode on most devices made after 2017, and gives you ~50% smaller files than VP8 at the same quality. Use VP8 only if you need to support a very old player or embedded device. Use AV1 if storage matters more than encode time and your viewers are on modern hardware (encoding takes 3-10× longer than VP9).

What CRF should I use for VP9 or AV1?

Start at CRF 32 for VP9 and CRF 30 for AV1. Lower the value if the output looks soft (try 28, then 25). Raise it if the file is still too big for your target (try 35, then 40). Each CRF step roughly changes file size by 15-20%. CRF below 20 is overkill for web playback; CRF above 45 introduces visible blockiness.

Will re-encoding reduce quality?

Yes — every lossy re-encode loses some data. The loss is small at high CRF/bitrate settings and barely visible above CRF 30. If you start with a low-quality WebM (heavily compressed YouTube rip, low-bitrate Twitch VOD), re-encoding at a lower bitrate will compound the loss. For best quality, re-encode from the highest-quality source you have available, not from an already-compressed copy.

Can I keep the audio untouched while only changing the video codec?

In a WebM container, the supported audio codecs are Opus and Vorbis. If your source is already Opus, the audio passes through cleanly during VP9/AV1 re-encodes. If your source is Vorbis, switching to Opus typically reduces audio overhead by 20-30% at the same perceived quality.

Is there a file size limit?

XConvert processes files in your browser session, so the practical limit is your device's available memory. Most modern laptops handle 1080p WebM files up to 2-4GB without trouble. For very large 4K source files, downscale resolution first or trim to a shorter segment.

How is this different from compressing WebM?

Re-encoding WebM gives you full codec and parameter control (codec swap, CRF tuning, resolution, trim, audio codec). Compress WebM is a guided flow that targets a specific output size or percentage with sensible defaults. Use compress when you have a target like "under 25MB"; use re-encode when you want to switch from VP8 to VP9 or change resolution.

Can I convert to a different container format instead?

Yes. Use WebM to MP4 for the most universal container (Apple devices, social media, video editors), WebM to GIF for animated previews, or WebM to MP3 to extract just the audio.

Does the converter work offline once the page loads?

Yes. After the page and conversion engine load, the actual encoding runs locally via WebAssembly. You can disconnect Wi-Fi mid-conversion and it will still finish — files never leave your browser.