Video Formats Explained: MP4 vs MOV vs WebM & Which to Use
When you try to upload a video and get the error "format not supported," or when a MOV file from your iPhone won't open on a Windows PC, the culprit is almost always the video format (container). Choosing the right format affects compatibility, file size, and quality. This guide explains the major video formats and tells you exactly which to use for each platform and situation.
Video Format Comparison Table
| Format | Common Codecs | Compatibility | File Size | Best For |
|---|---|---|---|---|
| MP4 | H.264, H.265 | Excellent (universal) | Small–Medium | YouTube, SNS, general sharing |
| MOV | ProRes, H.264 | Good (Apple-centric) | Medium–Large | iPhone recording, Mac editing |
| WebM | VP8, VP9, AV1 | Medium (Web-centric) | Very small | Website embedding |
| AVI | Xvid, DivX | Medium (legacy) | Large | Old Windows video files |
| MKV | H.264, H.265, etc. | Medium (Windows-focused) | Medium | Movies with multiple subtitles |
MP4 — The Universal King
Compatibility: Excellent / Recommended for: Everything
MP4 (MPEG-4 Part 14) is the most universally supported video format in the world. It plays on Windows, Mac, iOS, Android, every major web browser, and every major video platform including YouTube, TikTok, Instagram, X (Twitter), and Discord. When in doubt, use MP4.
H.264 vs H.265 (HEVC) — what's the difference?
The "codec" is the compression engine inside the MP4 container. H.264 offers excellent quality at reasonable file sizes and plays on virtually every device. H.265 (HEVC) achieves the same visual quality at roughly half the file size, but has slightly worse compatibility with older devices. For uploading to social media, use H.264. For personal storage where file size matters more, H.265 is the better choice.
MOV — Apple's Native Format
Compatibility: Good on Apple devices / Potential issues on Windows
MOV is the default video container used by Apple's QuickTime and is recorded natively by iPhones and Macs. It often contains high-quality ProRes or H.264 video, making it excellent for video editing workflows within the Apple ecosystem.
The issue: MOV files can have compatibility problems on Windows or non-Apple media players without additional codecs. If you're sending a video to someone whose device you're unsure about, convert it to MP4 first. Major social media platforms (YouTube, Instagram, TikTok) accept MOV, but MP4 is safer and often results in smaller file sizes.
WebM — The Web Developer's Format
Compatibility: All modern browsers / Limited on native apps
WebM was created by Google specifically for use in web browsers via HTML5 video. It uses VP8, VP9, or the newer AV1 codec, achieving significantly smaller file sizes than MP4 at comparable quality — ideal for keeping your website fast.
The trade-off: WebM is a web-only format. Older Safari versions on iOS had no native WebM support. It's not accepted by most social media platforms for uploads. Use WebM when you're embedding a video directly in a website and need the fastest load time possible. Provide an MP4 fallback for older browsers.
AVI and MKV — Legacy and Specialty Formats
AVI was once Windows' dominant video format but is now largely obsolete. AVI files are large, often lack modern codec support, and are not accepted by most social media platforms. If you have old AVI files, convert them to MP4.
MKV (Matroska) is a flexible container that can hold multiple video streams, audio tracks, and subtitle files in a single file — making it popular for movies and TV shows with multiple language options. However, it's not supported by major social media platforms for direct upload and has inconsistent native support on mobile devices.
Convert MOV to MP4 & Compress in One Step
Limitio's video compressor converts iPhone MOV files to lightweight, compatible MP4 entirely in your browser — no uploads to external servers. Perfect for Discord's 50MB limit or Gmail's 25MB cap.
Compress & Convert Video FreePlatform-by-Platform Recommendations
| Platform | Best Format | Size Limit | Notes |
|---|---|---|---|
| YouTube | MP4 (H.264) | 128GB / 12 hrs | MOV also accepted; H.265 for 4K |
| MP4 (H.264) | 4GB (Reels: 1GB) | Feed: up to 60 sec; Reels: up to 90 sec | |
| X (Twitter) | MP4 | 512MB | Max 2 min 20 sec for standard accounts |
| Discord (free) | MP4 | 50MB | Convert MOV first; compress if over limit |
| TikTok | MP4 / MOV | 287.6MB (web) | Vertical (9:16) strongly recommended |
| Website embedding | WebM + MP4 | Varies | Use WebM for speed; MP4 as fallback |
Frequently Asked Questions
Does converting MOV to MP4 reduce quality?
If done correctly, the quality loss is negligible or undetectable. When converting, use a high-quality or lossless setting for the output bitrate. Limitio's video compressor offers preset quality levels so you can choose the right balance for your use case.
My video is over 50MB — how do I send it on Discord?
Discord free accounts have a 50MB video limit. Compressing the video with a lower bitrate (while keeping the same resolution) or converting a MOV to a more efficient MP4 typically brings it under the limit. Use Limitio's "Discord" preset to automatically target the 50MB limit.
Should I film in MOV or MP4 on my iPhone?
Go to Settings → Camera → Formats. "High Efficiency" records in HEVC (H.265) MOV, which is smaller but less compatible. "Most Compatible" records in H.264 MP4/MOV, which works everywhere. If you often share videos with Windows users or on social media, "Most Compatible" avoids conversion headaches.
What's the best format for 4K video?
For archival and editing: MOV with ProRes (Apple) or MP4 with H.265. For uploading to YouTube or social media: MP4 with H.264 or H.265. H.265 handles 4K much more efficiently — a 4K H.265 file is often half the size of the equivalent H.264 file with nearly identical visual quality.
Can WebM replace MP4?
For website video embedding, WebM is often the better choice due to smaller file sizes. But for social media uploads, email attachments, or sending files to others, MP4 remains the standard. WebM is a supplementary format for web developers, not a universal replacement for MP4.