HEVC to MP4 (H.264) converter
A video that plays on your iPhone but shows a black screen on Windows is almost always HEVC. Turn it into H.264 MP4, the format everything plays.
Everything happens inside your browser, using your own computer’s memory. Your file is never uploaded, never stored, and nothing is sent to us — so there is no limit on how often you use this.
How converting HEVC to MP4 (H.264) works
At a glance
- Converts
- HEVC to MP4 (H.264)
- Runs on
- Your computer, inside this tab (WebAssembly)
- Fast route
- Seconds, no quality change — when the video inside already suits the new type
- Rebuild
- H.264 at CRF 23 — roughly real time at 1080p, when a re-wrap is not enough
- Keeps
- The picture and the first sound track. Subtitles and extra tracks are left out
How it works
iPhones save video as HEVC by default because it is half the size. The catch is that many Windows PCs, older browsers and some upload forms cannot decode it at all.
This rebuilds the picture as H.264 inside an MP4 — the one combination every device made in the last fifteen years can play.
To stop it happening, set the iPhone to Settings › Camera › Formats › Most Compatible. New recordings will be H.264 from the start.
Step by step
- Drop the videoIt opens in this tab. Nothing uploads. The first time, the browser downloads the 32 MB video engine and keeps it.
- Pick the new typeMP4 plays on everything and is the right answer almost every time. MOV is for Apple editing apps; MKV is for keeping.
- Leave the fast route onIt re-wraps when it can, in seconds and with no loss. If the video needs rebuilding, the tool says so and does it.
- Convert and downloadKeep the tab open while it works. The finished file stays in this browser until you press Delete.
Which setting for which job
| If you are… | Choose |
|---|---|
| An iPhone video shows a black screen on Windows | MP4 — it is HEVC, and it will be rebuilt as H.264 automatically |
| A WebM screen recording for Instagram or TikTok | MP4 |
| An MKV a phone or TV will not open | MP4 — a quick re-wrap when the video inside is H.264 |
| Handing footage to someone on Final Cut or iMovie | MOV |
| The file plays fine but is too big to upload | Not this tool — use Compress, which can change the type too |
| You need the subtitles or a second audio track kept | Not this tool — it keeps the picture and the first sound track only |
Under the hood
The technical detail, for anyone who wants to know exactly what happens to their file. Each line first says it plainly.
Container versus codec
The box, and what is in the box.
MP4, MOV and MKV are containers: they hold streams and describe how to play them. H.264, HEVC and AAC are codecs: the way each stream is compressed. A player needs to understand both.
Remux (stream copy)
A new box, the same contents.
With -c copy the compressed streams are moved into the new container unchanged. Nothing is decoded, so it is fast even on large files and loses nothing — but it only works when the new container accepts those codecs.
Transcode with libx264 at CRF 23
Rebuilt so everything can play it.
Each frame is decoded and re-encoded as H.264 with the veryfast preset. CRF 23 is a constant-quality setting — the encoder spends whatever bits each scene needs to look the same — and is x264's own default.
HEVC (H.265)
Why iPhone videos fail on some PCs.
HEVC files are about half the size of H.264 at the same quality, which is why iPhones use it. Windows needs a separately installed HEVC extension to decode it, and many browsers and upload forms cannot read it at all.
Stream selection
Picture and sound, nothing else.
The tool keeps the first video and first audio stream (-map 0:v:0 -map 0:a:0?) and drops subtitles and data streams (-sn -dn). Image-based subtitles cannot be stored in MP4 at all and would otherwise make the whole conversion fail.
yuv420p and fast start
Plays everywhere, starts at once.
Rebuilt video uses 8-bit 4:2:0 colour, the layout every player expects. MP4 and MOV files get their index (the moov atom) moved to the front, so they can start playing before they finish downloading.
Size ceiling and retry
Built to finish, not to crash.
A rebuild is capped at 2160p (4K), because 8K runs a browser out of memory. If a large file still runs out, the tool retries on its own at 720p; if that fails too, it tells you to shrink the file with Compress first.
Platform specs
What each platform accepts. MP4 with H.264 video and AAC sound is accepted by all three — which is exactly what the rebuild produces.
| Platform | Shape | Resolution | File size | Length | Format |
|---|---|---|---|---|---|
| Instagram Reels | 9:16 | 1440 × 2560 recommended | Up to 4 GB | Up to 15 minutes | MP4 or MOV · H.264 · AAC stereo, 128 kbps or more |
| TikTok | 9:16 recommended | 540 × 960 or larger | Up to 500 MB | — | MP4, MOV, MPEG, 3GP or AVI |
| YouTube Shorts | Vertical or square | — | — | Up to 3 minutes | — |
From each platform's own published specifications (Meta Ads Guide, TikTok Ads video specifications, YouTube Help), checked September 2026. “—” means the platform does not state it. Platforms change these; check before a big campaign.
If something goes wrong
| What you see | Why | What to do |
|---|---|---|
| It said it had to rebuild, and it is slow | The video inside does not suit the new container — usually HEVC or VP9 — so every frame is being re-encoded. | Let it run and keep the tab open. It is roughly real time at 1080p; 4K takes about four times as long. |
| The MP4 is bigger than the original MOV | HEVC is about twice as efficient as H.264, so rebuilding the same quality in H.264 takes more space. | Run the result through Compress, or use Compress in the first place — it converts and shrinks in one go. |
| Colours look washed out | The iPhone filmed in HDR; the rebuild writes standard-dynamic-range video and does not convert HDR brightness. | For clips you plan to post, turn off Settings › Camera › Record Video › HDR Video on the iPhone. |
| “Too large for a browser to convert” | Even at 720p, the file needed more memory than the browser gives one page. | Shrink it with Compress first, then convert the smaller file — or use a laptop rather than a phone. |
| Subtitles or a second language track are gone | The tool keeps the picture and the first sound track only, by design. | Keep the original file for those. For posting, burned-in captions are what the platforms show anyway. |
Privacy: your file stays on your computer
The files people convert are usually straight off a phone — family, customers, the inside of a shop. Converting them in your browser means none of it is uploaded to be converted somewhere else.
- What your browser downloads
- The page — and, the first time you use a video tool, the video engine: about 32 MB, then kept in your browser's cache.
- What it sends to us
- Nothing. There is no upload step, no copy on our servers and no account. The work happens in your computer's memory.
- How we know
- Our automated tests run every tool while recording every network request the page makes. A single upload fails the test.
- Where the result lives
- In this browser only, until you press Delete. A finished file is still here if you close the tab and come back; a job still running stops when the tab closes.
Questions
Why is my HEVC file a black screen on Windows?
Windows needs a separate HEVC extension, usually paid, to decode it. H.264 needs nothing.
Will the file get bigger?
Usually a little — H.264 is less efficient than HEVC. Compress it afterwards if size matters.
Is my file uploaded?
No. The conversion runs inside your browser, using your own computer's memory. The file never leaves your device.
Does this handle iPhone HEVC files?
Yes. That is the most common reason people land here: a .mov that will not play on Windows or will not upload. It is rebuilt as H.264 in an MP4.
Will I lose quality?
Not when the video only needs re-wrapping, which is the usual case for H.264 files. When it has to be rebuilt, CRF 23 keeps the difference invisible at normal viewing.
Why did my file get bigger?
HEVC is more efficient than H.264, so the same quality in H.264 takes more space. Compress can make it smaller, and can convert at the same time.
Can I convert to WebM?
Not yet — the WebM encoders a browser can run fail on real phone recordings. WebM files open here fine and can be saved as MP4, MOV or MKV.
Can I convert several files at once?
One at a time. The finished file stays in this browser until you delete it, so you can start the next straight away.
A tool makes a file fit. It does not make people watch to the end — that is the hook, the order of the shots, the captions and the music. See how Ruzz does it.
Other conversions
Other free tools
Compress video
Too big to upload, email or text? Make it small enough, without it looking bad. Takes a few minutes.
Crop to 9:16
Turn a landscape or square video into a vertical short for Reels, TikTok and Shorts.
Trim video
Cut the dead air off the start and end, or keep just the 30 seconds that matter.
Extract audio
Pull the sound out of a video as MP3, WAV or AAC.
Grab a cover frame
Pick any moment and save it as a vertical cover image.
Join clips
Filmed it in three takes? Put them end to end in one video — different shapes and silent clips are fine.
Video to GIF
Turn a moment into a GIF with real colours, not the grainy web palette.
Compress image
Shrink and resize a photo to JPG, WebP or PNG. Instant.
Change speed
Slow motion or sped up, from 0.5× to 2×, with voices at their own pitch.
Remove sound
Take the audio off a video in seconds, picture untouched — then add a trending sound in the app.
Resize video
Exactly 1080×1920, 1080×1350, 1080×1080 or 1920×1080 — the size each platform asks for.