Convert files
without uploading
them.

FAQ

Common questions

Is twineconvert really free?

Yes, completely free for every conversion, with no daily quotas, no signup, no upgrade-to-remove-watermark gates. The site runs on display ads in the SEO content areas of each tool page; the conversions themselves never have ads or limits. No paid tier exists.

How is it possible that nothing is uploaded?

Modern browsers ship a near-complete operating system: WebAssembly runs C / C++ / Rust libraries at near-native speed, the File API reads files directly off your disk, and the Blob API lets us hand the converted file back as a download, all without ever sending bytes to a server. The same libraries (FFmpeg, libheif, pdfjs, mammoth, web-ifc, jsquash, etc.) that upload-based converters run on their servers, we ship as WASM into your browser tab.

Is there a file size limit?

Practically, your limit is whatever your machine can hold in browser memory, usually 1–4 GB of RAM for the conversion's working set. We don't impose an artificial cap. Upload-based converters typically cap at 1 GB on the free tier because their servers cost money per gigabyte; ours don't, because there are no servers.

What about really sensitive files, bank statements, medical records, court documents?

Those are exactly the files this site exists for. A bank statement (OFX, QFX, QBO, QIF) or a medical export (Apple Health, DICOM) sitting on a third-party server, even briefly, is an unnecessary risk. Here, the conversion executes locally in your browser tab, we have no server that could store, log, or even see the file.

Why are some converters slow?

Conversions that involve OCR (image-to-text), heavy video encoding (FFmpeg transcoding), or large 3D meshes (IFC, STL) are CPU-bound and execute on your machine. The WebAssembly runtime is fast (typically 80–95% of native speed) but still bound by your CPU. Upload-based converters feel faster on small files because they trade your privacy for a beefier server; on large files, the upload time often makes them slower overall.

Will my browser hang on a big file?

The conversion runs in a Web Worker (a background thread), so the page stays responsive while it works. You'll see a progress indicator during long operations. If you do hit a memory ceiling, the tab will reload, your file is never lost because it never left your disk.

Is the code open source?

Yes, every line of the conversion engine is on GitHub at github.com/Achraf921/conversionEngine. You can audit which libraries handle which formats, fork it, run it locally without internet access, or submit fixes. The 192-converter test suite (registry integrity, real-file conversion validation, round-trip equivalence checks, adversarial fuzz tests) runs on every commit.

Do you support batch conversion?

Not yet, the current UI is one file at a time per tool page. Batch conversion is on the near-term roadmap; the engine itself is stateless and supports it, the UI just isn't wired up yet. Open an issue on GitHub if this is blocking you and it'll get prioritized.