Convert ProRes to MP4
Apple ProRes is the editing-friendly intermediate codec you love in Resolve or Final Cut and can't play on iOS. Wave re-encodes ProRes to H.264 in MP4 through your browser's hardware encoder. No 20 GB upload before anyone can watch a review copy.
What actually changes
Apple ProRes launched in 2007 as an editing intermediate: constant bit rate, GOP-of-1 (every frame is a keyframe), engineered to decode in software at multiple 4K streams simultaneously. It ships in seven flavours - Proxy (~45 Mbps at 1080p), LT (~102 Mbps), 422 (~147 Mbps), 422 HQ (~220 Mbps), 4444 (~330 Mbps with alpha), 4444 XQ (~500 Mbps), and RAW (dcraw-scale bitrates). All of them decode fine anywhere QuickTime is installed, and refuse to play anywhere else - Chrome, Safari, iOS, Android MediaCodec, Windows Media Foundation, most smart TVs.
MP4's spec lists ProRes as a technically-accepted codec, but the ecosystem doesn't back that up: no consumer player decodes ProRes-in-MP4 in the wild. Wave decodes every ProRes frame to raw pixels and re-encodes to H.264 through WebCodecs - the browser API that lets web pages use the device's hardware video encoder directly. On a machine with a hardware H.264 encoder (2015+ Intel Quick Sync, NVIDIA NVENC, Apple VideoToolbox), this runs at real-time or faster for 1080p sources. On browsers without WebCodecs H.264 (Firefox, older Safari), Wave falls back to the LGPL MPEG-4 Part 2 encoder shipped in the wasm ffmpeg core - slower and slightly less efficient, but same license-clean toolchain.
ProRes 4444 and 4444 XQ carry an alpha channel that was the whole point of choosing them over 422 HQ. MP4 has no widely-supported alpha codec, so Wave composites the alpha against black during the re-encode. If preserving alpha matters (green-screen keys, motion graphics with transparency, VFX plates), keep the source .mov and use it in workflows that respect alpha - After Effects, Motion, Nuke, Resolve. Deliver the MP4 for playback only.
The file-size reduction is dramatic and worth planning around. A one-minute 1080p ProRes 422 HQ master is roughly 1.6 GB; the H.264 MP4 that comes out is typically 40-80 MB at high visual quality - a 20-40x reduction. For 4K ProRes 4444 XQ, expect roughly ~4 GB to ~200 MB at the cost of the alpha channel and full colour depth. For review-copy delivery, that's exactly the trade-off you want; for archival or further editing, keep the ProRes.
Three steps.
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Step 1
Drop your ProRes .mov onto Wave. Any of the seven ProRes variants works - Wave inspects and detects the flavour.
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Step 2
Wave confirms Re-encode - the source decodes to raw pixels and re-encodes to H.264 through your browser's WebCodecs encoder.
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Step 3
Convert. 1080p ProRes runs at real-time or faster on hardware-accelerated systems; 4K runs at 2-4x real-time on modern GPUs. Save the MP4.
Answers, specifically.
ProRes 4444 alpha - does it survive?
No. MP4 has no alpha-carrying codec that consumer players decode. The alpha channel composites against black during the re-encode. For alpha preservation, keep the ProRes .mov as your working master and deliver the MP4 for playback only.
How much visual quality is lost?
At the H.264 bitrate Wave targets for 1080p, the visual difference from the ProRes source is well below the perceptual threshold on any consumer display. Studio-monitor critical review might flag block-boundary artifacts on high-detail or high-motion content; the delivery MP4 is not intended for critical review.
Can I export MP4 directly from DaVinci Resolve or Final Cut without the ProRes step?
Yes. Resolve and Final Cut both export H.264 MP4 directly and that is faster than exporting ProRes then converting. Wave is for the case where you already have the ProRes master and need MP4 - a client sends you a ProRes master, a colourist delivers ProRes for review, an editor hands off ProRes to a stakeholder who can't play .mov.
ProRes RAW to MP4?
Yes. Same re-encode path. The RAW variant carries per-pixel sensor data rather than a Bayer-demosaiced image, so the decode debayers on the way through. It's slower than the other ProRes variants but still runs locally in the browser.
My ProRes file is 60 GB. Will Wave handle it?
Wave caps at 8 GB per file. Above that, ffmpeg from the command line locally is the practical path: `ffmpeg -i input.mov -c:v h264_videotoolbox -b:v 20M -c:a aac -b:a 192k output.mp4` on macOS, `-c:v h264_nvenc` on NVIDIA, `-c:v h264_qsv` on Intel Quick Sync.
Frame rate handling?
Wave preserves the source frame rate exactly. A 23.976 fps ProRes stays 23.976; a 59.94 fps ProRes stays 59.94; a 29.97 drop-frame stays 29.97 drop-frame. Timecode metadata is copied through when the ProRes source carries it.
Colour space and HDR?
Rec.709 SDR ProRes converts cleanly to Rec.709 MP4. HDR sources (Rec.2020 with PQ or HLG transfer) go through the same re-encode; the resulting H.264 MP4 preserves the colour tags. Playback on an HDR-capable display shows the intended tone mapping; on SDR displays, the player handles the fallback tone map.
Two-pass encoding for better quality-per-bitrate?
Not in the current build. WebCodecs H.264 is single-pass with the encoder's built-in rate control. For delivery to a bitrate budget with best quality, ffmpeg with `-pass 1` then `-pass 2` locally is still the reference workflow.