"Your browser can't decode this file's format"
The file is a type we support, but it uses a codec your browser can't read.
Last updated October 2, 2026
Video and audio files are containers. An MP4 or MKV can hold many different codecs inside, and Okaysize uses your browser's own decoders to read them. Some codecs, such as HEVC (H.265) on some systems or old formats like WMV, aren't available in every browser.
What to try
Open the page in a recent Chrome or Edge on a computer, which support the widest range of codecs. Or export the file again from the app that made it, choosing H.264 MP4.
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