MKV to MP4 Converter

How to Convert MKV to MP4 Online

1. Upload Your MKV File: Drag and drop, or click "+ Add Files" to select MKV files from your computer. Batch upload is supported, and large multi-GB rips work fine because processing runs on our servers rather than a small server upload cap.
2. Pick a Quality Preset: Default is "Very High (Recommended)", which keeps the source close to lossless for most H.264/H.265 sources. Switch to Specific File Size to hit a target (MB or %), Constant Bitrate for streaming-friendly output, Variable Bitrate for smaller files at the same perceived quality, or Constant/Constraint Quality (CRF) for hand-tuned encodes (lower CRF = higher quality, range 0–51 for H.264).
3. Resize or Trim (Optional): Under Video Resolution, pick a Preset Resolution (4320p down to 144p), enter Width × Height, or use Resolution Percentage to scale down. Under Trim, switch from Unchanged to Time Range and set start/duration in hours:minutes:seconds.milliseconds — useful for clipping a single episode out of a season pack.
4. Convert and Download: Click "Convert" and grab the MP4. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared.

Why Convert MKV to MP4?

MKV (Matroska) is an open container announced on 6 December 2002 and formalised as IETF RFC 9559 in October 2024. It is excellent for archiving — it can hold any number of video, audio, and subtitle tracks with chapter markers — but its niche-software origins mean a lot of consumer hardware never adopted it. MP4 (MPEG-4 Part 14, ISO/IEC 14496-14) is the universal playback container: every smart TV, console, phone, browser, and editor accepts it.

• Play on phones, TVs, and consoles — iOS, Apple TV, PlayStation 4/5, Xbox Series X/S, Chromecast, Roku, and most smart TVs play MP4 natively but skip or transcode MKV. iPhone's Photos app and AirDrop both refuse MKV outright.
• macOS-native workflow — QuickTime, Quick Look previews, iMovie, Final Cut Pro, and Photos all open MP4 directly; MKV requires VLC or IINA as a third-party player and won't import into Apple's editors.
• Social and streaming upload — YouTube, Instagram, TikTok, X (Twitter), Facebook, Vimeo, LinkedIn, and Reddit accept MP4 directly. Most reject MKV outright or transcode it server-side, which can re-compress your video and drop subtitle tracks.
• Editor compatibility — Premiere Pro, DaVinci Resolve, Final Cut Pro, and CapCut all import MP4 cleanly; MKV support is patchy and often requires remuxing first.
• Hardware decode — MP4 with H.264 or H.265 hits hardware decoders on essentially every chipset from the last decade (Apple A-series, Qualcomm Snapdragon, Intel Quick Sync, NVIDIA NVDEC), so playback is smooth and battery-efficient. MKV often falls back to software decoding on the same hardware.
• Streaming and progressive download — MP4 supports the faststart flag that moves metadata to the head of the file, letting browsers play before the download finishes. MKV is poorly suited to HTTP streaming.

MKV vs MP4 — Container Comparison

Remux vs Re-encode — What's the Difference?

Two different operations can turn an MKV into an MP4, and it's worth knowing which is which. This converter always re-encodes — it never stream-copies; a remux is what desktop tools like ffmpeg's -c copy or MKVToolNix perform.

Every conversion here takes the re-encode column: at XConvert's "Very High (Recommended)" preset the fresh encode is visually indistinguishable from the original, and when you don't pick a codec the source codec family is kept (H.264 in → H.264 out), so there's no cross-codec generation loss. Streams MP4 doesn't accept — DTS audio, FLAC — are converted to MP4-legal codecs in the same pass.

Frequently Asked Questions

Will I lose quality converting MKV to MP4?

The conversion always re-encodes — it is not a container rewrap, so the output is a fresh encode rather than a copy of the original bytes. In practice the loss is invisible: the default Very High preset encodes at the visually-lossless CRF tier (18 for H.264, 17 for HEVC), and with no codec selected the source codec family is kept, so an H.264 MKV becomes an H.264 MP4 with no cross-codec generation loss. Streams MP4 doesn't accept (DTS, FLAC, TrueHD) are converted to MP4-legal codecs; the result is visually and audibly indistinguishable from the source at normal viewing distance.

What happens to multiple audio tracks (e.g., English + Japanese dub)?

MKV supports unlimited audio tracks natively, and so does MP4 — but consumer playback software handles MP4 multi-track inconsistently. QuickTime, VLC, and modern Android players surface multiple tracks; some smart-TV and older phone players only expose the first track. The primary audio is always preserved; for guaranteed multi-language playback, keep the MKV archive in parallel.

Will embedded subtitles survive the conversion?

This depends on the format. MKV typically carries SRT, ASS/SSA, VobSub, or PGS subtitles. MP4 only natively carries mov_text (the MPEG-4 Timed Text codec, ISO/IEC 14496-17). Plain SRT can be converted to mov_text and travel as a soft subtitle track; styled ASS/SSA subtitles either lose their styling on conversion or need to be burned into the picture (hardcoded). If subtitle fidelity matters, archive the MKV alongside the MP4.

Why does my iPhone play the MP4 but refuse the MKV?

iOS's video stack only registers .mp4, .m4v, and .mov extensions. The Photos app, Files preview, AirDrop, and most third-party apps won't open an .mkv even when the underlying H.264 stream would play fine. After conversion, the same content plays in Photos, can be AirDropped, and works in iMovie. See also our MOV converter for AirDrop-optimised output.

Is the conversion lossless if the source is already H.264/AAC?

Not bit-identical — XConvert re-encodes the streams rather than rewrapping them, so the output is a fresh encode, not a byte copy of the input. In practical terms the difference is invisible: the default preset encodes at the visually-lossless CRF tier and keeps the source codec family, so an H.264/AAC MKV comes back as an H.264/AAC MP4 that is hard to tell apart from the source. Expect the file size to differ somewhat from the original rather than match it exactly.

Can I convert a large MKV (5 GB Blu-ray rip, full season pack)?

Yes. Multi-gigabyte files are supported, and because processing happens on our servers on our servers there is no small server-side upload cap to worry about. For 4K Blu-ray rips you may want to drop resolution to 1080p under Video Resolution → Preset Resolutions if the target device is a phone — it cuts file size roughly to a quarter.

Should I pick H.264 or H.265 inside the MP4?

H.264 (AVC) plays on absolutely everything from 2007 onward and is the safest pick for broad sharing. H.265 (HEVC) cuts file size roughly in half at the same visual quality but requires hardware decode support — fine on iPhones since the iPhone 6 (2014) and modern Android, but older smart TVs and browsers may struggle. For YouTube/social uploads pick H.264; for personal archives where you control the players, H.265 saves storage.

How do I just trim out a section instead of converting the whole thing?

Set Trim → Time Range and enter start time and duration. For pure trimming without container conversion, use the dedicated MKV trimmer — it keeps the source as MKV. If you also want a smaller file, see compress MKV or, after this conversion, compress MP4. Once it's an MP4 you can also make your video smaller to hit a tighter size target.

Is there a file count limit, account, or watermark?

No. Convert as many files in one session as you like, no sign-up, no watermark, and no per-file caps — everything is processed on our servers. The Conversion runs on our servers, so your files aren't stored on a server after download.