NEW · FFmpeg.wasm · 100% Browser-Based

Free Video Converter

Convert between MP4, MOV, WebM, MKV, AVI, and GIF entirely in your browser. No upload, no signup, no watermark. Runs FFmpeg.wasm locally.

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Drop a video file
MP4 · MOV · WebM · MKV · AVI · GIF
Files stay on your device · Never uploaded

Why Do This in Your Browser?

Most video format problems are solved by switching containers and codecs, not by re-shooting. A QuickTime MOV won't play in Discord; a Sony AVCHD won't import into Premiere on Windows; a phone-shot MP4 with HEVC video won't open on older laptops. The fix is a container + codec conversion — exactly what FFmpeg has done from a command line for 20 years.

This tool wraps the same FFmpeg engine in a browser. Drop a video in, pick a target format, and the conversion runs locally on your CPU via WebAssembly. No upload, no watermark, no time limit. For most desktop laptops, a 5-minute 1080p clip converts in 30–90 seconds depending on the format pair.

How It Works

When you pick a target, the tool selects sensible defaults for that format: MP4 uses H.264 + AAC for maximum compatibility; WebM uses VP9 + Opus for smaller files at the same quality; MOV preserves H.264 in an Apple-friendly container; MKV keeps the source codec when possible (no re-encode, faster); AVI uses MPEG-4 + MP3 for legacy software; GIF generates a palette + dithers down to under 256 colors.

Where possible, the tool copies streams instead of re-encoding (MP4 → MKV is usually a stream copy, taking seconds instead of minutes). When a codec change is required, quality is preserved at CRF 23 — visually identical to the source for most content.

Tip: If your goal is to fit a specific file-size cap (WhatsApp 16MB, Gmail 25MB), the Video Compressor does this directly without you having to guess at bitrates. For tighter control over GIF output (frame range, fps, color palette), use the dedicated GIF Maker.

Common Use Cases

MOV → MP4 for Sharing
Apple devices record in MOV. Most messaging apps and Windows tools prefer MP4. One-click conversion, no quality loss.
MP4 → WebM for Web
WebM with VP9 averages 30–40% smaller than MP4 at the same visual quality. Worth it for hero videos on landing pages.
MKV → MP4 for Compatibility
Downloaded MKVs often don't play on phones or in browsers. Stream-copy to MP4 keeps quality with no re-encode.
Video → GIF for Threads & Slack
Quick conversion of short clips to animated GIFs for chat reactions and email attachments.
Source File Standardization
Convert mixed-source footage (MOV + MP4 + AVI) to a single container before editing.
Phone-Recorded HEVC Issues
Newer iPhones record HEVC by default — convert to H.264 for editors and old browsers.

How We Compare

Honest read on free, paid, and self-hosted options for this kind of job:

UDT Video Converter (this tool): Free, browser-based, runs FFmpeg.wasm locally. All formats. No upload, no watermark, no signup.
CloudConvert: Free tier 25 conversions/day, queue waits. $8–$50/mo paid plans. Cloud — your video goes through their servers.
Convertio: Free tier capped at 100MB and watermarks output. $10/mo. Cloud.
Online-Convert: Free with ads + 100MB cap. $9/mo. Cloud.
FFmpeg (command line): Free, open-source, runs locally — definitive answer for batch conversions. Requires installation and command-line use. This tool is the same engine, wrapped for one-off browser use.

Frequently Asked Questions

Which video formats are supported?
MP4, MOV, WebM, MKV, AVI, and GIF, both as input and output. The tool also reads less common containers (FLV, WMV, 3GP) for input even though they're not in the output list.
Will quality be lost?
Quality is preserved at CRF 23 for codec changes (visually identical to source for most content). Stream copies (e.g., MP4 → MKV) are byte-exact — no re-encode happens.
Are my videos uploaded anywhere?
No. Conversion runs entirely in your browser via FFmpeg.wasm. The 32MB engine downloads once, caches, and runs locally thereafter.
How long does a conversion take?
A 5-minute 1080p clip typically converts in 30–90 seconds on a modern laptop. Stream copies (no codec change) take 2–5 seconds regardless of length. Phones run roughly 2–3x slower than laptops.
Why is my converted video larger than the original?
Some conversions trade size for compatibility. MP4 → MOV is roughly equal; MP4 → AVI can be 20–40% larger because AVI lacks modern codec features. For size-focused conversions, prefer the compressor tool.
Can I convert without re-encoding?
When the target container supports the source codec, yes — the tool detects this and stream-copies. Common cases: MP4 ↔ MKV, MP4 ↔ MOV (both H.264). MP4 → WebM always re-encodes (different codecs).
What's the maximum file size?
Limited by browser memory. Modern laptops handle 1–2GB; phones cap around 500MB.
Does GIF conversion add a watermark?
No. The GIF output is clean. Note that converting a 1-minute 1080p video to GIF produces a 50MB+ file — for most uses, a short clip (≤10s) at reduced resolution gives a more usable result.

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