Video converter

How to convert a video

Why convert videos?

Container and codec mismatches stall everyday workflows: a phone shooting MOV when the editor wants MP4, a screen recorder spitting MKV that a CMS rejects, an old AVI archive that needs to ship on the web as WebM, or a marketing team standardizing every clip into H.264 MP4 for cross-platform playback. Our converter probes the input to detect codecs and frame parameters, then picks the cheapest valid path — copying streams losslessly when the source already matches the destination container, otherwise re-encoding with H.264 + AAC for mp4/mov and VP9 + Opus for webm. It runs in a Rust service wrapping ffmpeg in the cloud over an encrypted connection (TLS); your files are auto-deleted after conversion and never shared, while a content-hash cache makes repeat conversions instant. No watermark, no signup, no upsell.

Containers vs codecs: the thing to understand first

Video files confuse people because two different things share the same name in casual speech. A container — mp4, mkv, webm, mov, avi — is the wrapper. It bundles the video stream, one or more audio tracks, subtitles, chapters and metadata into a single file, and defines how a player finds and syncs them. A codec — H.264, H.265 (HEVC), VP9, AV1 — is the compression algorithm that turns raw frames into a manageable size. The two are largely independent: the same H.264 video can sit inside an mp4 or an mkv, and the same mp4 container can hold H.264 or H.265. When a player 'can't open' a file, the culprit is usually the codec inside, not the container extension.

This is why simply renaming a .mkv to .mp4 rarely works, and why a real converter has to look at both layers. This tool inspects the streams first, then either re-wraps them into the requested container without touching the picture (fast, lossless) or re-encodes to a codec the target container supports well — H.264 + AAC for mp4 and mov, VP9 + Opus for webm.

The formats this tool handles

• MP4 — the universal default. Usually H.264 video with AAC audio. Plays on essentially every device, browser and editor; the format to reach for when a video needs to 'just work'.

• WebM — the open web format, built around the VP9 (or VP8) codec and Opus audio. Smaller than MP4 at similar quality and royalty-free, ideal for background videos and HTML5 players on sites you control.

• MOV — Apple's QuickTime container, the native output of iPhones and many cameras. Technically similar to MP4 and often holding the same H.264 stream, but less universally accepted by web tools, so it's a common source you'll want to convert to MP4.

• MKV (Matroska) — a flexible open container that can hold almost any codec plus multiple audio tracks and subtitles. Popular for archived films and screen recordings, but poorly supported in browsers, so it's frequently converted to MP4 for sharing.

• AVI — a legacy Microsoft container from the 1990s. Still turns up in old archives and some cameras; large and dated, it's almost always worth converting to a modern format.

Codecs and containers at a glance

How the common containers pair with codecs, and where each fits:

Why MP4 with H.264 is the compatibility default

If you only remember one recommendation, make it this: when in doubt, export MP4 with H.264 video and AAC audio. H.264 has been hardware-accelerated in phones, laptops, TVs and browsers for well over a decade, so it decodes smoothly even on modest devices and drains less battery than newer codecs that fall back to software decoding. Its licensing situation is settled, which is why every website upload form, messaging app and video editor accepts it. Newer codecs like H.265 and AV1 compress better — meaning a smaller file at the same quality — but their playback support is still patchier, especially in browsers and older hardware. Unless you have a specific reason to chase file size and control where the video plays, MP4/H.264 is the safe, boring, correct choice.

Quality, size and bitrate

For a re-encoded video, bitrate is the main lever on quality and size. Bitrate is how many megabits per second the codec spends describing motion and detail; higher bitrate means a sharper picture and a bigger file. The right number depends on resolution and content: fast-moving, detailed footage (sport, games) needs more bits than a mostly static talking-head clip at the same resolution. As a rough guide, 1080p web video looks good around 6–10 Mbps with H.264, while 720p is comfortable at 3–5 Mbps. More efficient codecs reach the same visual quality at a lower bitrate — VP9 and H.265 typically need 30–50% fewer bits than H.264 for the same result, which is the whole point of using them.

Because video is lossy, every re-encode discards a little detail. A single conversion at a sensible bitrate is visually clean, but re-encoding the same clip over and over slowly softens it. Where the source stream already matches the target container, this tool copies it verbatim rather than re-encoding, so there's zero additional loss.

When should you convert?

• An upload form rejects your file — a site accepts MP4 but not MOV or MKV. Convert to MP4/H.264 and it goes through.

• A video won't play on a particular device — the container is fine but the codec inside isn't supported. Re-encoding to H.264 fixes it.

• You want a smaller file — moving to WebM (VP9) or lowering the bitrate cuts size for web delivery or email.

• You're standardizing a library — converting every clip to one format (usually MP4) makes editing and playback predictable.

• You're publishing on your own site — WebM gives you a lighter self-hosted video with a wide-enough modern-browser reach.

Frequently asked

Related tools