You've got a video file. You want to watch it. But your browser says it can't play MKV files. Or the codec isn't supported. Or you need to download some plugin. Or convert it first. Sound familiar?

Seedr's player handles all of that. Upload your file — any format — and click play. We convert incompatible formats automatically in the background. No codec packs to install. No conversion software to download. No waiting for a file to process before you can watch. Most videos start playing within seconds.

This isn't a basic HTML5 player that only handles MP4. This is a full-featured video player built to handle the formats people actually have.

Supported Video Formats

Containers

The container is the "wrapper" that holds video, audio, and subtitle tracks together:

• MKV (Matroska) — The most versatile container. Supports multiple audio tracks and multiple subtitle tracks. Seedr handles MKV files fully, including track switching during playback.
• MP4 / M4V — Standard web format. Usually plays directly without conversion.
• AVI — Older format, still common. Full support.
• MOV — Apple's format. Works great.
• WebM — Google's open format. Native browser support.
• WMV / ASF — Windows Media formats. Supported.
• FLV — Flash video. Still works despite Flash being dead.
• MPEG / MPG — Classic format. Supported.
• 3GP — Mobile video format. Supported.
• OGV — Ogg video. Supported.
• TS / MTS / M2TS — Transport stream formats from cameras and broadcasts. Supported.

Video Codecs

The codec is how the video is compressed inside the container:

• H.264 / AVC — The most common codec. Plays directly in all browsers.
• H.265 / HEVC — Newer, more efficient codec. Native support in Safari and Edge; transcoded for other browsers if needed.
• VP8 / VP9 — Google's codecs used by YouTube. Native browser support.
• AV1 — Next-gen codec. Supported where browsers allow.
• MPEG-4 — Older but common. Supported.
• MPEG-2 — DVD-era codec. Supported.
• WMV / VC-1 — Windows codecs. Transcoded automatically.
• Xvid / DivX — Classic codecs from the 2000s. Still work.

Audio Codecs

• AAC — Standard. Direct playback.
• MP3 — Universal. Direct playback.
• AC3 / E-AC3 (Dolby Digital) — Common in high-quality releases. Transcoded for browser playback while preserving quality.
• DTS — Premium audio format. Transcoded to compatible format.
• FLAC — Lossless audio. Supported.
• Opus / Vorbis — Open formats. Native support.
• PCM / WAV — Uncompressed audio. Supported.

MKV Files: Full Support

MKV is the most popular container for high-quality video, and for good reason — it supports features that MP4 doesn't. Seedr handles MKV files completely:

Multiple Audio Tracks (v2)

Many MKV files include multiple audio tracks — original language, dubbed versions, commentary tracks. On Seedr v2, switch between them during playback without restarting the video. The track selector shows available options. (Requires v2 — Premium members skip the waitlist.)

Multiple Subtitle Tracks

Same for subtitles. English, Spanish, forced subtitles only, SDH (subtitles for the deaf and hard of hearing) — switch between them on the fly. Seedr supports:

• SRT — Text-based subtitles (embedded or external files)
• VTT — Web subtitle format
• ASS / SSA — Styled subtitles with fonts, colors, and positioning
• PGS — Blu-ray image-based subtitles

Subtitle Timing Adjustment

Subtitles out of sync? Use the timing adjustment control to shift subtitles forward or backward in increments as small as 0.1 seconds. No need to edit the subtitle file — adjust on the fly.

How Format Conversion Works

Not every format can play directly in web browsers. When you add a file that needs conversion, here's what happens:

1. Instant analysis — Seedr identifies the file format, codecs, and tracks within seconds.
2. Background processing — If conversion is needed, it happens on our servers. You'll see progress in the interface.
3. Streaming while converting — For most files, you can start watching before conversion finishes. We process from the beginning of the file first.
4. Original preserved — The original file stays intact. Conversion creates a streamable version alongside it.

What Plays Directly (No Conversion)

• MP4 with H.264 video and AAC audio — instant playback
• WebM with VP8/VP9 video — instant playback
• Many MKV files with compatible codecs

What Needs Conversion

• MKV with DTS or AC3 audio (audio gets transcoded)
• AVI files (container converted)
• HEVC video on browsers without native support
• Unusual or very old codecs

Conversion typically takes 1-5 minutes depending on file size and complexity. Most files are ready before you finish reading this paragraph.

Player Features

• Adaptive bitrate streaming — Quality adjusts to your connection. Starts fast, improves as it buffers.
• Quality selector — Choose your streaming quality. v2 with Premium unlocks resolutions above HD.
• Playback speed — 0.5x to 2x speed without audio pitch distortion.
• Picture-in-Picture (v2) — Pop out video to a floating window while you browse.
• Chromecast — Cast to your TV with one tap.
• Resume playback (v2) — Pick up where you left off, even on different devices.
• Keyboard shortcuts — Space for play/pause, arrows to seek, M to mute, F for fullscreen.
• Theater mode — Expanded player without going full-screen.
• Mobile optimized — Touch-friendly controls, gesture support, orientation lock.

Seedr vs. Other Online Players

Audio Files Too

Seedr isn't video-only. The audio player handles:

• MP3, AAC, M4A — Standard formats
• FLAC, ALAC, WAV — Lossless formats for audiophiles
• OGG, Opus — Open formats
• WMA — Windows audio

Features: continuous playback, queue management, album art display, Chromecast support, background playback.

Works With Media Servers

All these formats work seamlessly with media server software. Connect Seedr to your existing setup:

• Plex: MKV, MP4, AVI — Plex handles them all when connected via WebDAV or FTP. Plex + WebDAV guide →
• Jellyfin: Open-source alternative with excellent format support. Jellyfin setup →
• Kodi: Native Seedr addon for direct playback of any format. Kodi addon →
• Roku: Stream your library directly on Roku devices. Roku setup →

Common Questions

Can I play MKV files in my browser?

Yes. Seedr plays MKV files directly in your browser, including multi-audio and multi-subtitle MKV files. No plugins or codec packs needed.

What about high-quality video?

Seedr v2 supports quality options from 360p up to 2160p (4K), limited by your plan. Free accounts stream at 360p. v1 maxes out at 720p. Premium members get instant v2 access.

Do I need to wait for conversion?

Usually no. Many files play directly. When conversion is needed, you can often start watching while it's still processing.

What's the maximum file size?

Limited only by your storage quota. Free accounts get 2GB. Paid plans go up to 10TB. Individual files can be as large as your available space.

Can I download the original file?

Yes. Streaming and downloading are both options. The original file is always preserved — conversion creates a separate streamable version. Learn more about streaming vs downloading →

Does it work on mobile?

Yes. The player is fully responsive and works on iOS and Android. Install as a PWA for the best experience.

What if a format doesn't work?

Rare, but possible with very obscure codecs. Contact support — we may be able to add support or suggest alternatives.