HEVC to H.264 Converter

HEVC and H.264 are codecs, not containers

This is the one conversion on this site where the file extension tells you nothing. HEVC (H.265) and H.264 are both stored inside an MP4 almost all of the time, so the iPhone clip your PC refuses and the one it plays happily can both be called .mp4. The container is the box; the codec is how the pictures inside it were compressed. Renaming the file relabels the box and changes nothing inside it, which is why the "just change the extension" advice fails for HEVC and works for a MOV.

It is also why this page behaves differently from the rest of the site. MOV to MP4 and TS to MP4 are container swaps: one H.264 stream is lifted out of one wrapper into another in seconds, bit for bit. HEVC to H.264 means every frame is decoded and drawn again by a different compressor. There is no shortcut here or anywhere, and anything advertising a lossless H.265-to-H.264 conversion is misusing the word.

What actually differs between the two

H.264 arrived in 2003 and became the format everything on earth learned to decode. HEVC arrived a decade later with one goal: the same picture at roughly half the bitrate. It succeeded, which is why phones, drones and action cameras record in it, and why the files trip over anything that predates it or never licensed it.

The last row matters more than it looks. Output is 8-bit 4:2:0 with the moov atom moved to the front, the combination that makes an MP4 both universally decodable and able to start playing before it has finished downloading.

Picking a quality that does not hurt

Because this is a real re-encode, the quality setting is the only decision that matters. Low, Medium and High are CRF 28, 23 and 20 with x264's veryfast preset. CRF is constant quality rather than constant bitrate: the encoder spends bits where the picture is complicated and saves them where it is not, so a static interview and a handheld forest shot each come out looking like themselves instead of each being forced into the same megabits per second. High (CRF 20) is close enough to the source that most people cannot pick the difference on a phone or a laptop panel, and it is what you should use for anything you cannot re-shoot.

Expect the file to grow. You are leaving a codec designed to be twice as efficient, so an HEVC clip re-encoded at a genuinely similar quality is commonly larger than the original. That is the price of playing everywhere, not a sign of a fault. If size matters more than fidelity, drop the resolution to 1080p rather than reaching for Low quality: throwing away pixels you were never going to see costs far less visible detail than crushing every pixel you keep.

10-bit, HDR, and what happens to it

If your iPhone is set to record HDR, or your camera writes 10-bit HLG, the source is 10-bit HEVC. H.264 has a 10-bit profile on paper, but almost nothing that people actually own will play it, so converting to it would defeat the purpose of the conversion. This tool writes 8-bit 4:2:0, which is what "H.264 that plays everywhere" means in practice.

What does not survive the trip

Only the first video stream and the first audio stream are kept. Subtitle tracks are dropped, extra audio tracks (a second language, a commentary, a separate camera mic) are dropped, and chapters do not carry over. The phone app drops them too. The tool counts those tracks before it converts anything and says so in plain words, so it is never a surprise you find afterwards. Choosing MKV does not rescue them: only one video and one audio stream survive here whatever the output container, so a file whose extra tracks matter belongs in a desktop tool.

The honest limits of doing this in a tab

The engine is FFmpeg compiled to WebAssembly, served from this domain and run in a Web Worker. Nothing is uploaded, there is no server involved, and once your first conversion has fetched the engine, the converter keeps working with the network switched off. The cost of that architecture is speed: the build is single-threaded, so a re-encode runs at roughly real time for 720p, slower than real time for 1080p, and slower again when the source is HEVC, because HEVC decoding is itself heavier than H.264 decoding. A ten-minute 4K clip is a long wait, not a quick one.

There are two hard numbers. Files over 2 GB are refused, because a 32-bit WebAssembly heap cannot address them. Past a few hundred megabytes the page warns you, because the job needs roughly three times the file size in free memory. Neither is a business decision a paid tier removes; both are properties of the platform.

This is also the honest case for the app. Video Converter on iPhone and the Android version use the device's own hardware encoder — VideoToolbox or MediaCodec — silicon built for exactly this job, so long or 4K footage finishes far faster and there is no size ceiling. The app always re-encodes and has no stream-copy mode, so for a container swap the browser wins; for a heavy HEVC job, the app does.

The files that send people to this page

Nearly everyone who arrives here has one of five symptoms, and all five share a cause.

• Windows plays the sound over a black rectangle. Windows has not shipped HEVC decoding by default for years; it is a Store add-on, free only if your PC maker pre-installed its version. Converting the file fixes it for good, on every PC you send it to — the full story is in why HEVC will not play on Windows 11.
• An Android phone shows a grey thumbnail. Older or budget Android hardware has no HEVC decoder, and the gallery gives up silently rather than explaining. See iPhone video that will not play on Android.
• An editor imports audio only. DaVinci Resolve's free edition, and some Premiere installs, will not decode HEVC on every platform, so the clip lands as a waveform. Resolve refusing an MP4 is almost always this.
• PowerPoint shows a black box in the meeting room. A deck that plays on your machine and not on the conference PC is usually an HEVC clip meeting an Office install without the decoder — see PowerPoint cannot play this media.
• A TV, car stereo or older console ignores the file. These decode in fixed hardware; if that hardware predates HEVC, no update helps. H.264 in an MP4 is what they were built for.

If you are not sure which codec you actually have, drop the file into the converter above and read the panel it prints: container, video codec and profile, resolution, frame rate, audio codec and channel layout, and the track counts. Nothing leaves your machine to produce that readout. Checking what is inside a video file explains what each line means, and if it turns out you have an MKV rather than an HEVC problem, MKV to MP4 will usually finish in seconds without re-encoding anything.