Any file up to 500 MB. Drop several files and they come back as one ZIP. Many image, audio and video conversions run in your browser; anything else is uploaded and removed within the hour.
Easily convert your legacy AVI video files into the modern MKV container format. This tool is perfect for users who need to update their video library for better compatibility with modern media players.
AVI (Audio Video Interleave) is an older container format that often struggles with modern codec support and subtitles. MKV (Matroska) is a versatile, open-standard container designed to hold an unlimited number of video, audio, and subtitle tracks within a single file. Converting from AVI to MKV involves re-packaging the data streams; while the underlying video data remains intact, the file structure is updated to the more robust Matroska standard.
Since both AVI and MKV are containers, the conversion process performs a remuxing or light re-encoding. Because both formats involve lossy compression, repeated re-encoding will degrade quality, but a direct container swap keeps visual fidelity stable.
We built this project so anyone can convert files without paywalls, accounts, or hidden limits. Here is what that promise means in practice.
Every converter on ConvertX is free to use: no trials, no premium tiers, and no credit packs. We will never put core conversion features behind a subscription. Whether you convert one photo or a hundred files a week, the price stays zero.
Many image, audio, and video conversions run entirely in your browser. Your files never leave your device for those jobs. When server processing is required for documents or specialized formats, uploads are handled securely and removed automatically — typically within one hour.
A quick guide to strengths and trade-offs of popular formats — so you pick the right one before converting.
Clips, streams, screen recordings, and movies.
Common extensions: MP4, WebM, MOV, MKV, AVI, MPEG
Raster and vector graphics for web, print, and photography.
Common extensions: PNG, JPG, WebP, AVIF, GIF, SVG, HEIC, TIFF
Office files, PDFs, ebooks, and plain text.
Common extensions: PDF, DOCX, XLSX, PPTX, ODT, EPUB, TXT
Music, podcasts, voice recordings, and sound effects.
Common extensions: MP3, WAV, FLAC, OGG, AAC, M4A, OPUS
