Mac video compression
How to shrink videos for any destination — codecs, CRF, and the math behind file size
Video compression on Mac is a deeper rabbit hole than image compression. Codecs (H.264, HEVC, AV1), modes (CBR vs CRF), presets (ultrafast through veryslow), audio (AAC, Opus, copy), containers (MP4, MOV, MKV), hardware vs software encoding, and dozens of destination-specific quirks (Discord's 25 MB cap, iMessage's silent fallback to email, WhatsApp's automatic re-encode). The vocabulary alone takes a few hours to understand.
This is our hub for everything we've written about getting a video down to a reasonable size without losing visible quality. The practical answer for most cases: H.264 at CRF 23, preset medium, AAC audio at 128 Kbps — a recipe that fits 90% of the 'compress this video for upload' problems Mac users actually have.
We ship QuickVid Compress because we wanted the simplest possible workflow — drop a file, pick a mode, save — without configuring codec menus every time. Below are the technical articles for when you want to understand what's happening, plus the destination-specific recipes for Discord, iMessage, Gmail, and a dozen others.
The app
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May 16, 2026 · 8 min read
How to compress video for Discord, iMessage, and email on Mac
Every chat app has a different upload limit, and every codec choice has a different trade-off. A practical guide to shrinking videos on macOS for the platforms you actually share to.
May 17, 2026 · 6 min read
'iMessage attachment too big' — how to fix it on Mac and iPhone
Why iMessage rejects your video, what the actual size limits are, and three ways to compress a video down to a working size — including a one-click Mac fix.
May 17, 2026 · 3 min read
iMessage / 微信 视频太大发不出去？Mac 上 3 种压缩办法
为什么 iMessage 拒绝你的视频、各平台的真实大小限制（不是官方说的那样）、以及一键修复方案。
May 17, 2026 · 10 min read
What is CRF in video compression? A practical guide for non-engineers
CRF is the single most useful knob in modern video encoding — but most guides explain it wrong. Here's what it actually does, with concrete recommendations.
May 17, 2026 · 9 min read
How to compress an MP4 without losing quality (Mac, 2026)
"Visually lossless" is achievable. Here's the recipe — codec, CRF, preset — and how much smaller you can realistically expect.
How it compares to other tools
Reference data
Browse compression recipes by destination — size limits and exact codec/CRF/bitrate settings for Discord, iMessage, Slack, Gmail, and 8 other platforms.
Frequently asked questions
What's the best codec for compressing video on Mac?
H.264 (libx264) is the universal default — every device made since 2004 can play it, and the quality-vs-size tradeoff is well understood. HEVC (libx265) produces 30-50% smaller files at the same quality but only works reliably on Apple ecosystem devices and modern browsers. AV1 produces the smallest files but encoding is 5-20x slower and not universally supported. For 95% of cases, H.264 is the right answer.
What does CRF do in video compression?
CRF (Constant Rate Factor) controls perceptual quality — lower number means higher quality and larger file. For H.264, CRF 18 is visually transparent, CRF 23 is the libx264 default for web video, CRF 28 produces noticeably-compressed-but-acceptable output for chat-app uploads. Each step of +6 roughly halves the file size at the cost of visible quality.
Why is my compressed video lower quality than I expected?
Most fast-presets (ultrafast, veryfast, faster, fast) trade visible quality for encoding speed. For 'compress without quality loss' switch to 'medium' or 'slow' preset and use CRF 18-23 in H.264 (or CRF 22-26 in HEVC). Hardware encoding via VideoToolbox is fast but quality is consistently worse than software encoding at the same file size.
What's the difference between MP4, MOV, and MKV containers?
MP4 is the universal container — everything plays it. MOV is Apple's preferred container (same H.264 video inside, slightly different metadata structure); QuickTime treats MOV as native. MKV (Matroska) supports more codecs, multiple audio tracks, and subtitles but isn't supported on iOS or most chat apps. For sharing: always MP4. For Apple-ecosystem internal use: MOV is fine. For archival with subtitles: MKV.