Trim WebM Video

How to Trim a WebM Video Online

1. Upload Your WebM File: Drag and drop your .webm file or click "Add Files" to select one. Multiple WebM files can be queued and trimmed in the same session — useful when chopping a stream archive into individual highlight clips.
2. Set Start Time and Duration: Open the Trim panel and pick Time Range. Enter a Start Time and a Duration in plain seconds (e.g. 45.5) or switch to HH:MM:SS.sss for frame-level precision on longer videos. The trim is destination-duration based, so a Start of 00:02:10.000 and Duration of 00:00:30.000 gives you exactly 30 seconds beginning at the 2:10 mark.
3. Tune Quality, Codec, and Resolution (Optional): Under Video Codec, keep VP9 (the WebM default) for the best size/quality balance, switch to VP8 for WebRTC or older-Android playback, or pick AV1 when you want roughly 30% smaller files than VP9. Under Video Compression, choose a Quality Preset (Highest through Lowest), Target File Size % (Smart Scaling will adjust resolution to hit it), Specific File Size in MB/KB, Constant Quality (CRF), or Constraint Quality (CRF with a max-bitrate cap for predictable streaming). Under Audio Codec, Opus is the WebM default; Vorbis is the legacy option. Video Resolution lets you keep the original or drop to a preset (1080p, 720p, 480p, 360p), scale by percentage, or enter custom width/height.
4. Convert and Download: Click Convert. The trimmed WebM is processed in your browser session — no sign-up, no watermark, no email gate.

Why Trim a WebM Online?

WebM is the open, royalty-free container Google built for the web, pairing VP8/VP9/AV1 video with Opus or Vorbis audio. It is what YouTube, Reddit, Twitter/X, and most CDNs serve to Chromium and Firefox browsers when they can, because VP9 typically delivers 30–50% smaller files than H.264 at matching quality. The trade-off: a WebM you downloaded with yt-dlp, recorded from OBS, or grabbed from a Twitter video link is often longer than you need, larger than a chat app accepts, or contains a section you want to share standalone.

• Cut a clip out of a stream archive — A 4-hour Twitch VOD downloaded as WebM is unwieldy. Trim a 90-second highlight at frame-accurate timestamps and you have something postable to Discord, Slack, or Bluesky.
• Hit Discord's 10 MB free upload — Discord lowered its free attachment cap from 25 MB to 10 MB in September 2024. Use Specific File Size = 10 MB with Smart Scaling and the tool down-rezzes the trimmed segment to fit.
• Strip an intro/outro before re-uploading — Animated logos, sponsor reads, and end cards inflate file size and watch time. Trim them out and your effective bitrate goes up for the same target file size.
• Extract one scene for a tutorial or bug report — Sending a 12-minute screen recording is rude. A 20-second VP9 clip at 720p lands under 5 MB and plays natively in every modern browser without re-encoding on the recipient's side.
• Prep a clip for a GIF conversion — WebM-to-GIF works best on short loops. Trim to 3–6 seconds first, then run convert-webm-to-gif — you skip the lost-quality round-trip of trimming a GIF after the fact.
• Reduce a recording to fit a CMS upload field — WordPress, Notion, and Ghost typically cap inline video uploads at 50–100 MB. Trimming combined with Target File Size lets you publish without spinning up an external CDN.

WebM vs MP4 for Trimmed Clips

Property	WebM	MP4
Default video codec	VP9 (also VP8, AV1)	H.264 / AVC (also H.265, AV1)
Default audio codec	Opus (also Vorbis)	AAC (also MP3, ALAC)
Licensing	Royalty-free, open	Patent-licensed (MPEG-LA)
Browser playback	Chrome, Firefox, Edge, Opera, Safari 14.1+	Universal, including older Safari/iOS
Compression at same quality	30–50% smaller (VP9 vs H.264)	Baseline
Hardware decode coverage	Good for VP9 on 2017+ devices; AV1 on 2020+	Universal for H.264
Native upload acceptance	Limited — many platforms re-encode	Direct upload on YouTube, Instagram, X, Reddit
Editing tool support	Strong in FFmpeg, Shotcut, DaVinci Resolve 18+	Universal

If your trimmed clip is destined for a social platform's native upload pipeline, convert it to MP4 after trimming — Reddit accepts MP4/MOV for native uploads and re-encodes WebM uploads server-side.

Codec and Compression Quick Guide

Setting	When to pick it	Trade-off
VP9 + Opus (default)	Web embedding, Chrome/Firefox audiences, archive	Slower encode than VP8; weaker iOS <14 support
VP8 + Vorbis	WebRTC, very old Android, MediaRecorder fallback	~35% larger than VP9 at matching quality
AV1 + Opus	Future-proofing, lowest bitrate at given quality	Slowest encode; Safari needs M3 / iPhone 15 Pro+ for HW decode
Quality Preset = Highest	Master copy, small trim window, archive	Largest file
Constant Quality (CRF) ~30 (VP9)	Best quality-to-size ratio at unknown bitrate	File size not predictable in advance
Target File Size %	Hitting a relative size (e.g., 25% of original)	Re-encodes; quality varies with content
Specific File Size (MB)	Hitting a hard upload cap (10 MB Discord, 25 MB Gmail)	Resolution may auto-scale down
Constraint Quality	Streaming with bandwidth ceiling	Slightly more complex than plain CRF

Frequently Asked Questions

Can I trim a WebM without re-encoding so quality is preserved exactly?

This tool always re-encodes the trimmed segment so you can simultaneously change codec, resolution, bitrate, and audio. If lossless trimming is the goal, pick Quality Preset = Highest or Constant Quality (CRF) with a low CRF value (around 18–23 for VP9), keep the codec at VP9, and leave resolution unchanged. The output is visually indistinguishable from the source for typical viewing. For true stream-copy trimming with zero re-encoding you would need a desktop tool like FFmpeg with -c copy, which only cuts at keyframes and gives you less precise edit points.

What time format should I use for frame-accurate cuts?

Use HH:MM:SS.sss from the dropdown next to the time field. The milliseconds component lets you specify edits like 00:01:23.500, which is roughly half a frame off at 30 fps and exact at 60 fps. Plain seconds works fine for short clips but gets awkward past about 10 minutes — typing 673.5 is more error-prone than 00:11:13.500.

How do I trim a WebM to fit Discord's 10 MB free upload?

Set your trim points first. Under Video Compression, choose Specific File Size and enter 10 MB. Smart Scaling will adjust bitrate (and resolution, if needed) to land under the cap. Discord Nitro Basic raises it to 50 MB and full Nitro to 500 MB. If you cannot get below 10 MB while keeping resolution acceptable, lower the duration further or switch the codec to AV1 — AV1 gives roughly 30% smaller files than VP9 at the same perceived quality, which often makes a borderline file fit.

Will Twitter/X, Reddit, or Instagram accept a trimmed WebM directly?

Twitter/X and Instagram do not accept WebM uploads — they require MP4 (H.264 + AAC). Reddit's native uploader also expects MOV or MP4. After trimming, run convert-webm-to-mp4 and you'll have a file these platforms will take without re-encoding it server-side (which often degrades the visible quality of your clip). YouTube does accept WebM uploads but transcodes everything regardless.

Can I change the codec while I trim?

Yes. Under Video Codec, switch from the default VP9 to VP8 (for WebRTC or legacy Android), AV1 (smaller files, slower encode), H.264, or H.265. Audio Codec accepts Opus, Vorbis, AAC, MP3, FLAC, and several PCM variants. Re-encoding to AV1 on a long trim segment is slow — for a multi-minute clip, expect noticeably longer processing than VP9, but the output file is typically the smallest possible at a given visual quality.

Can I trim and resize the WebM in one pass?

Yes — set the trim points, then adjust Video Resolution. Pick a preset (1080p, 720p, 480p, 360p), enter a custom width/height, or scale by percentage. Both operations happen in a single encode pass, which is faster and gives slightly better quality than trimming first and resizing later. Down-rezzing also dramatically reduces file size — going from 1080p to 720p at the same bitrate cuts pixels by 56%.

My WebM has VP8 + Vorbis from an old MediaRecorder capture. Should I upgrade?

If the original is short and bandwidth is not a concern, leaving it as VP8 + Vorbis is fine. If you plan to archive it, re-host it, or trim and re-share, upgrade to VP9 + Opus during this trim — VP9 typically delivers 30–50% smaller files than VP8 at matching quality, and Opus is dramatically better than Vorbis at low audio bitrates (it is the modern successor and is the default for new WebM files).

Does the trim include or exclude the Duration endpoint?

Duration is exclusive of any frame past your specified length. A Start of 10.000 and Duration of 5.000 includes frames from the 10.0 s mark up to (but not including) the 15.0 s mark. If you want to keep precisely the frame at 15.000, bump Duration to 5.040 (one extra 1/24 s frame) or 5.034 (one extra 1/30 s frame).

Is anything uploaded to your servers, and is there a file size limit?

Files are processed in your browser session and not stored on our servers after your session ends. The free tier handles single-file trims up to several hundred MB without trouble; if you have a multi-GB stream archive, compress the WebM first or split the source before uploading. There is no watermark and no sign-up requirement.