Why MOV to MP4 does not have to cost quality
MOV and MP4 are close relatives. Both are containers: boxes that hold a video stream, a sound stream and some information about them. An iPhone video is usually H.264 or HEVC video with AAC sound inside a MOV box, and an MP4 box can hold exactly the same streams. So converting does not need to touch the picture at all. The streams are lifted out of one box and put into the other, frame for frame.
Many converters re-encode anyway: they decode every frame and compress it again, which takes minutes, changes the picture slightly and often makes the file bigger or smaller for no reason. This tool copies by default, and then proves it: after converting, it compares every video frame in the MP4 with the original, byte for byte, and tells you the result.
What we measured
We converted test videos in Chrome on a Windows PC (2 October 2026, several runs) and checked the results with a separate MP4 reader, not just with this tool:
| Video | Time | Frames identical | Size before → after |
|---|---|---|---|
| 12 s, 1080p MOV, H.264 + AAC | about 0.1 s | 360 of 360 | 12.16 MB → 12.16 MB |
| Same video, filmed upright (rotation 90°) | about 0.1 s | 360 of 360, still upright | 12.16 MB → 12.16 MB |
| 60 s, 1080p, 60.8 MB | about 0.3 s | 1,800 of 1,800 | 60.8 MB → 60.8 MB |
| 12 s, 1080p, re-encoded as H.264 | about 8 s | re-encoded (by choice) | 12.16 MB → 12.10 MB |
| 12 s, 1080p HEVC (iPhone-style), re-encoded as H.264 | 3.5 to 10 s | re-encoded (by choice) | 6.88 MB → 9.4 to 10.2 MB |
Copying is fast because nothing is computed: the time is mostly reading and writing the file. An upright phone video stays upright, because the rotation note in the file is carried across with it. The size barely changes, because the content is the same; only the box around it is new.
iPhone videos and HEVC
Since iOS 11 in 2017, iPhones record in HEVC (H.265) by default, the “High Efficiency” setting. HEVC makes smaller files, but not everything plays it: some Windows PCs, older TVs, some browsers and some upload forms only accept H.264. Copying keeps the video HEVC, so if the MP4 still will not play where you need it, choose Most compatible. That mode decodes the video and encodes it again as H.264, which plays almost everywhere. H.264 needs more data than HEVC for the same picture: in our test, an HEVC clip re-encoded at its own bit rate came out visibly softer (40.5 dB against the original instead of 42.7), so for HEVC sources the tool uses 1.5 times the bit rate (41.2 to 41.4 dB over two runs). The MP4 ends up a third to half bigger than the MOV. It takes longer than copying and changes the picture slightly, so use it only when you need it.
To avoid the question for future videos, the iPhone can record H.264 directly: Settings → Camera → Formats → Most Compatible. That setting also switches photos from HEIC to JPG; for photos you already have, use HEIC to JPG. If an iPhone video will not play on your PC at all, our guide on why iPhone videos won't play on Windows walks through how to check the format and every way to fix it.
Location and recording date
Phones store the place a video was recorded inside the MOV file, as GPS coordinates. To see what happens to it, we wrote location and date entries into our test MOV the way an iPhone does, converted it, and searched the MP4 byte by byte. The location was gone: neither the Apple location entry nor the older QuickTime one survived. The recording date was kept as the day (2026-07-14), but not the time of day or the time zone.
The tool reads both before converting and tells you what it found and what the MP4 keeps. If you are sharing a video publicly, losing the location is usually what you want. If you are archiving family videos and the exact time matters, keep the original MOV as well.
Can I just rename .mov to .mp4?
Sometimes it plays, because the two formats share the same structure. But the file still describes itself as
QuickTime: the first bytes of our test MOV say qt, while the converted file says isom,
avc1 and mp41, the labels MP4 players and upload checks look for. A renamed file can
also carry things MP4 does not define, such as uncompressed sound or extra tracks from editing apps. Converting
writes a real MP4 and drops what does not belong, in about the same time it takes to rename.
Limits
- The finished MP4 is built in your browser’s memory, so a video of several gigabytes may be too large on a phone or an older computer. A desktop browser handles typical phone videos easily.
- ProRes and other professional codecs cannot be copied into MP4 or decoded in a browser.
- Converting does not make a file smaller. For that, use Compress Video; to cut the start or end without re-encoding, Trim Video; to remove the sound, Mute Video.
Sending the video by email after converting? Our guide on how to send a video that is too big for email covers the limits of each provider. Everything on this page runs in your browser: the video is never uploaded.