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 FLV (Flash Video) files into the modern, versatile MKV (Matroska) container. This tool is perfect for users looking to modernize their video library for playback on contemporary media players.
FLV was the standard for web streaming in the Flash era, but it lacks support in modern hardware and software. MKV, conversely, is an open-standard container designed to hold virtually any number of video, audio, and subtitle tracks. When converting from FLV to MKV, the tool repackages the existing video and audio streams into the Matroska structure without requiring a complex codec change, ensuring the process is efficient.
Because both FLV and MKV are containers, this process involves re-wrapping the data. However, as both formats typically use lossy compression codecs like H.264 or Sorenson Spark, repeated re-encoding can lead to minor quality degradation.
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
