AVI is one of the oldest container formats still in circulation, and its age is exactly why it causes so much friction today. It predates HTML5 video, predates the smartphone, and was designed for the Video for Windows codec ecosystem of the mid-1990s. Browsers have never supported AVI playback natively, iPhones and iPads cannot play it at all without a third-party app, and many modern editing tools, upload forms, and streaming platforms simply reject it outright. MP4 with H.264 video and AAC audio, by contrast, is the closest thing the internet has to a universal video standard — every browser, every phone, every smart TV, and every social platform accepts it without complaint.
Because AVI can contain a huge range of different video codecs — some AVI files hold H.264 already, others hold decades-old codecs like DivX, Xvid, Cinepak, or Indeo — this converter does not assume it can simply repackage the data unchanged. It fully decodes the video stream and re-encodes it as H.264 at a CRF (Constant Rate Factor) of 23, a setting widely regarded as visually lossless for most content, and encodes the audio as AAC. This full re-encode step is slower than a simple remux, but it is what guarantees the output MP4 works everywhere, regardless of what obscure codec your original AVI happened to use.
Once you have an MP4, Trim Video and Compress Video both work directly on it, or convert to MKV if you need a container with broader codec/subtitle support.
