About Apple ProRes (QuickTime)
Apple introduced ProRes in 2007 as the codec professional video would be edited in, and it stuck: nearly two decades later it is the default currency of postproduction. Its trick is intra-frame compression — every frame is stored complete, none is derived from its neighbors — which makes scrubbing a timeline instant and re-exporting generation after generation essentially painless. The price is size: ProRes spends hundreds of megabits per second, from the leaner 422 Proxy and LT proxies through 422 and 422 HQ up to 4444 and 4444 XQ, which add an alpha channel for motion graphics.
That design makes ProRes superb inside an edit suite and stubborn everywhere else. Browsers, phones, TVs, and upload forms have no idea what to do with it — it was never meant for delivery, so playback support outside professional software is close to nonexistent. Everyone who works with ProRes eventually needs the same thing: a watchable copy in a normal format.
Convertmaxxing decodes ProRes with a decoder built into the page — no editing software or plugin needed — and converts it to MP4 for delivery. ProRes always re-encodes (delivery players expect codecs like H.264, so there is no lossless repackaging shortcut), and ProRes RAW, being unprocessed sensor data rather than encoded video, is not supported. Creating ProRes files isn’t supported either; converting away from ProRes is the real-world need.
Strengths
- Every frame stands alone, so timeline scrubbing and cutting are instant in any editor
- Visually lossless 10-bit (and 12-bit in 4444) quality that survives repeated edit-and-export cycles
- The postproduction standard — every professional editing and grading tool accepts it
- The 4444 variants carry an alpha channel, making it a workhorse for motion graphics
Limitations
- Enormous files — minutes of footage can consume gigabytes of disk
- Virtually unplayable outside professional software: browsers, phones, and TVs refuse it
- A working format, not a delivery format — sharing ProRes always means converting first
- Creating ProRes isn’t supported here, and ProRes RAW capture files can’t be read
Intra-frame versus inter-frame, and why editors care
Delivery codecs like H.264 achieve their small files largely by storing most frames as differences from other frames. A keyframe appears every few seconds, and the frames between it are described as "what changed since". That is enormously efficient for playback, where you start at the beginning and move forward. It is miserable for editing, because landing on an arbitrary frame means finding the previous keyframe and reconstructing everything in between — which is why scrubbing a long H.264 file feels sluggish and why cuts can land in unexpected places.
ProRes stores every single frame complete and independent. Nothing is derived from a neighbour, so any frame is immediately available without reconstructing anything. Scrubbing is instant, cutting is frame-accurate by nature, and multi-stream playback in a timeline stops being a struggle. The cost is bitrate — ProRes 422 HQ runs around 220 Mbps at 1080p where a good H.264 delivery file might use 10 — but disk space is cheap compared with an editor’s time.
Choosing a variant, and why conversion always re-encodes
The family is a ladder. 422 Proxy and 422 LT are lightweight versions for offline editing on modest hardware. 422 is the general-purpose workhorse, and 422 HQ is the common mastering choice for most professional delivery. Above those, 4444 and 4444 XQ add a fourth channel for alpha transparency and higher bit depth, which is why motion graphics and visual effects work lives there. All of them decode here.
What none of them can do is travel to a delivery container untouched. A lossless rewrap works when the source codec is something the target container already accepts — H.264 moving from MOV to MP4, for instance. No mainstream delivery player expects ProRes, so every ProRes conversion decodes the frames and re-encodes them into H.264 or similar. That is a genuine generation of loss, though starting from a visually lossless master means the result is as good as a delivery encode gets. Note also that ProRes RAW is a different thing entirely — unprocessed sensor data rather than encoded video — and is not supported here.
Frequently asked questions
- Why are my ProRes files so enormous?
- Because every frame is stored complete rather than as a difference from its neighbours, and at a high bitrate. ProRes 422 HQ runs roughly 220 Mbps at 1080p, so a minute of footage is around 1.6 GB. That is the deliberate trade: disk space in exchange for instant scrubbing and quality that survives repeated re-exports.
- Do I need Final Cut or QuickTime to convert ProRes here?
- No. The ProRes decoder is built into the page and runs in your browser, so no editing software, codec pack, or plugin is required. Your footage is decoded on your own machine and never uploaded anywhere.
- Can ProRes convert losslessly to MP4?
- No — ProRes always re-encodes. A lossless conversion is only possible when the target container already accepts the source codec, and no mainstream delivery player expects ProRes. The frames are decoded and re-compressed to H.264 or similar, which is a real generation of loss, though starting from a pristine master keeps the result excellent.
- Is ProRes RAW supported?
- No. Despite the shared name it is a fundamentally different format — unprocessed sensor data awaiting demosaicing, rather than encoded video frames. All the standard ProRes variants are supported: 422 Proxy, 422 LT, 422, 422 HQ, 4444, and 4444 XQ.