What is Codec?
A plain-English definition, and the tools that work with it.
A codec is the method used to compress and decompress audio or video: it's the 'how' inside a file. H.264, H.265 (HEVC) and AV1 are common video codecs. A file's container (MP4, MOV) is separate from its codec, which is why two MP4s can behave differently.
- The container (MP4, MOV, WebM) is the box. The codec (H.264, HEVC, AV1) is how the video inside is encoded.
- Newer codecs like HEVC and AV1 compress smaller but need more support and processing power.
- 'The file won't play' is often a codec issue, not the container, re-encoding to H.264 usually fixes it.
Tools for Codec
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Video Converter
Convert video between MP4, WebM, MOV, AVI, MKV and GIF in your browser with FFmpeg. Pick a target format, tune MP4 quality, preview the result and download. Nothing is uploaded.
Video Compressor
Compress video in your browser with FFmpeg, shrink MP4, MOV, WebM and MKV files with a simple quality slider, see the exact bytes and percentage saved next to a live preview, then download. Nothing is uploaded.
MP3 Converter
Convert any audio to MP3 in your browser, WAV, M4A, AAC, OGG, FLAC and more to a clean, universally-playable MP3 with a bitrate you choose. Preview the waveform, encode locally with lamejs, then download. Nothing is uploaded.
Extract Audio from Video
Pull the audio track out of any video and save it as MP3, WAV, AAC, M4A or OGG, right in your browser. Drop an MP4, MOV or WEBM, pick a format, preview and download. Nothing is uploaded.
Codec problems we solve
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Frequently asked questions
Related terms
- MP4MP4 is the most widely supported video format, a container that holds video and audio together. Because virtually every device, editor, browser and platform plays MP4, it's the safe default for sharing, uploading and playing video anywhere.
- BitrateBitrate is how much data is used per second of audio or video, measured in kbps or Mbps. A higher bitrate means more detail and a larger file. A lower bitrate means a smaller file with more compression. It's the main dial for the quality-versus-size trade-off.
- MOVMOV is Apple's QuickTime video format, the default for videos recorded on iPhones and Macs. It's high quality and works natively in Apple's ecosystem, but some Windows PCs, apps and platforms can't play it, which is why MOV is often converted to MP4.
Keep exploring
Problems we solve
Definitions
From the blog
- How to Add a Watermark to a Video: Brand and Protect Your Clips
- How to Merge Video Clips Into One File (Without Re-Encoding When You Can)
- How to Extract Audio From a Video: Save the Sound as MP3
- How Browser-Based Video Editing Works (ffmpeg.wasm and the Privacy Angle)
- How to Trim a Video Online, Cut Clips Privately, With No Upload
Common tasks
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