Why ConvertMathly is different
Most online converters upload your files to a remote server, make you wait in a queue and limit file sizes unless you pay for a subscription. ConvertMathly takes a different approach: the conversion engines — FFmpeg for video and audio, PDF.js and pdf-lib for documents, libarchive for archives — run directly in your browser through WebAssembly. That means your files stay on your device, there is nothing to upload or download from a server, and there is no reason to charge a subscription.
Files are processed on your device and never uploaded. Close the tab and they are gone.
No account, no daily cap, no queue and no watermark — convert as much as you want.
The same engine used by professional video tools, running in your browser via WebAssembly.
Windows, Mac, Linux, Chromebook, iPhone and Android — any modern browser, nothing to install.
How it works
- Drop your filesDrag files onto the box above or click Choose Files. The format is detected automatically.
- Pick the output formatEach file gets its own “to” menu with every format it can be converted to.
- Convert & downloadResults are ready in seconds. Download each file or all of them as one ZIP.
Frequently asked questions
Is ConvertMathly really free?
Yes. Every tool is free with no sign-up, no watermark, no queue and no daily limit. The site is supported by non-intrusive ads.
Are my files uploaded to your servers?
No. Unlike most online converters, ConvertMathly processes files entirely inside your web browser using JavaScript and WebAssembly. Your files never leave your device.
What file formats can I convert?
Hundreds of conversions across video (MP4, MOV, MKV, AVI, WEBM…), audio (MP3, WAV, M4A, FLAC, OGG…), images (JPG, PNG, WEBP, HEIC, SVG, ICO, TIFF…), PDF, Word, EPUB, Excel/CSV, and archives (ZIP, RAR, 7Z, TAR).
Is there a file size limit?
There is no artificial limit. The only limit is your device memory — most computers handle files up to 1–2 GB.
Does it work on my phone?
Yes. ConvertMathly works in Safari and Chrome on iPhone and Android, as well as on Windows, Mac, Linux and Chromebook.