Vidlora guide
MP4 vs MKV and the right video download quality
Choosing a video format means making three separate decisions: the container that holds everything, the codec that compresses the picture, and the resolution that sets how much detail there is. People often mix these up, which leads to files that will not play or are far larger than needed. This guide separates the three, compares MP4 and MKV honestly, and gives file-size figures so you can pick a quality that suits your device and storage.
7 minute read
Container, codec and resolution are different things
A container such as MP4, MKV, MOV or WebM is a box that holds a video stream, one or more audio streams, subtitles and metadata. The codec, for example H.264, H.265 (HEVC), VP9 or AV1, is the method used to compress the picture inside that box. Resolution, such as 720p or 2160p, is the pixel dimension of each frame. A file called .mp4 can contain H.264 or H.265, and two MP4 files with the same resolution can differ by a factor of three in size if one uses a more efficient codec or a higher bitrate. When a file will not play, the cause is usually an unsupported codec rather than the container. Knowing which of the three you are choosing makes the format list far less confusing.
MP4: the safe default
MP4 (MPEG-4 Part 14) is supported natively by phones, tablets, smart TVs, game consoles, browsers, social platforms and almost every editing application. Paired with H.264 video and AAC audio, it is the closest thing to a universal video file. It supports a single video track with multiple audio tracks and basic subtitles, and it can place metadata at the start of the file so playback begins before the download finishes, which suits web video. Its weaknesses are limited support for exotic subtitle formats and some audio codecs. Choose MP4 when you are not sure where the file will be played, when you will upload it to a social platform, or when you will import it into an editor. For most people, most of the time, MP4 is the right answer.
MKV: flexible but less universal
MKV (Matroska) is an open container designed for flexibility. It can hold many audio tracks, multiple subtitle languages, chapter markers, attachments such as fonts, and almost any codec including VP9, AV1 and H.265. That makes it popular for archiving films, anime and lectures with several languages. The downside is compatibility: Windows and macOS need a capable player such as VLC, many TVs handle it only partially, iPhones do not play it natively, and many editors need it converted first. MKV is also less convenient for web streaming. Choose MKV when you want to keep separate subtitle or audio tracks, or when the best available stream uses a codec MP4 does not carry cleanly. If the file will be shared or edited, convert it to MP4 afterwards.
Resolution and what you actually see
Resolution describes pixels: 360p is 640x360, 720p is 1280x720, 1080p is 1920x1080, 1440p is 2560x1440, 2160p (4K) is 3840x2160 and 4320p (8K) is 7680x4320. Each step multiplies the pixel count: 4K has four times the pixels of 1080p. Whether you can see the difference depends on screen size and viewing distance. On a 6-inch phone, 720p and 1080p look almost the same; on a 55-inch TV from three metres, 4K is visible if the source is clean. A 1080p video that was upscaled from 480p will never look sharp. Pick the resolution that matches the display, not the largest number in the list. For tutorials with small on-screen text, 1080p matters more than for talking-head videos.
File size by quality
Size grows quickly with resolution. At typical web bitrates, 360p runs about 0.7 Mbps (5 MB per minute), 720p about 2.5 Mbps (19 MB per minute), 1080p about 5 to 8 Mbps (40 to 60 MB per minute), 1440p around 12 Mbps (90 MB per minute) and 4K 20 to 45 Mbps (150 to 340 MB per minute). So a 20-minute video is roughly 100 MB at 360p, 380 MB at 720p, 1 to 1.2 GB at 1080p and several gigabytes at 4K. 8K files are enormous and few devices can play them smoothly. Efficient codecs help: AV1 or VP9 can match H.264 quality at about 30 to 50 percent less data, but older hardware may struggle to decode them. If storage or mobile data is limited, 720p is the sweet spot.
Matching format to device
For an iPhone or iPad, MP4 with H.264 or HEVC plays everywhere; WebM and MKV generally do not. Android phones handle MP4 and most WebM. Smart TVs vary widely: a USB stick with a 1080p H.264 MP4 is the most reliable combination, while 4K HEVC or AV1 depends on the model and its age. Browsers play MP4 and WebM. Video editors prefer MP4 or MOV with H.264 or HEVC, though long-GOP formats can feel slow when scrubbing. If you are copying files to an older device, drop to 720p and H.264. If a file stutters on a TV but plays well on a computer, the TV cannot decode the codec or bitrate; converting to a more conservative H.264 MP4 usually fixes it.
Frame rate, HDR and other details
The format list may also show frame rate (24, 30, 60 fps) and HDR. A 60 fps video looks smoother for sport and gaming but needs roughly 1.5 times the data of the same clip at 30 fps. Film and most talking-head content looks fine at 24 or 30 fps. HDR (high dynamic range) stores a wider range of brightness and colour, but on a screen without HDR support it can look washed out or dim, so only choose HDR if your display supports it. Variable frame rate recordings from phones can cause audio sync problems in some editors, which is another reason to convert to a constant frame rate before editing. When you are unsure, stay with standard dynamic range and the frame rate the source uses.
A simple decision guide
Ask three questions. Where will it be played? If the answer is a mix of devices or the web, choose MP4. How much space and data do you have? If limited, choose 720p. Do you need multiple subtitle or audio tracks? If yes, choose MKV and keep it for your own player. For lectures and tutorials, use 1080p so text stays legible. For music videos and clips on a phone, 720p is enough. For archiving something you own, keep the highest quality available and convert copies for sharing. For editing, download the best quality and avoid repeated re-encoding. If a file will not open, check the codec in a metadata viewer, then convert to H.264 MP4. Following this guide avoids most format headaches.
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